A

Assessing productivity of free breeding fish species

in farmer-managed irrigation tanks in the

Dry Zone, Sri Lanka

by Carlos Yanes-Roca

I

Acknowledgments

I would like to thank too many people for their help during my thesis:

Dr. Dave Little for giving the chance to work in this project and the patience of going

through all my grammatical mistakes.

Francis Murray for his help and support in Sri Lanka

All the assistant researches and house mates, for helping with the translations and other

things… (Susantha, Prythanta, Bandara, Tharaka, Deeptha and Yasantha)

To Rasak, for looking after me during the lonely weekend and for his magnificent lime

sodas.

To Dr. Sarah for his academic help.

The volleyball team of Galgamuwa great distraction after hard day of work.

To Astrid Holzer for her moral support during my days in Sri Lanka.

Of course my family for their unconditional support.

And finally to my computer for not crashing in Sri Lanka.

II

Abstract

. Man made reservoirs (tanks) in Sri Lanka are found throughout the country representing

nearly all the country’s surface water (2% of the total land surface), but are particularly

important in the Dry Zone. The current study was carried out to assess if tanks have

potential as a central element in the development of aquaculture.

The analysis of seasonality, water catchment, location and water input were the main

factors used to classify the potential of various types of tank for fish culture. These

factors, together with the analysis of peoples livelihood’s around the tanks and the impact

of macrophytes on tank productivity, has led to the conclusion that seasonal tanks (e.i.

those that dry out completely) have the potential for development of a sustainable

aquaculture.

In an analysis of the priorities of water usage, fisheries was found to be lower than

irrigation and bathing and potential conflicts were identified that constraint development

of fish culture in Dry Zone tanks. Other constraints such as macrophyte infestation do not

represent a ma jor impediment since the infestation occurs less severely in seasonal tanks

where the main species are relatively easy to remove.

The development of fish culture in the Dry Zone may improve the poor nutrition of

people living there that are particularly dependent on freshwater fish, but a holistic

approach to understanding constraints and peoples’ priorities will be essential to

increasing fish yields on a sustainable basis.

III

Table of Contents

Acknowledgements Abstract

1 Introduction………………………………………………………………………1-28

1.1 Geography

1.2 Climate

1.3 Vegetation and fauna

1.4 Social-economic Aspects

1.5 Inland water resources

1.6 Agriculture

1.7 Fisheries

1.8 Macrophytes

1.9 Objectives

2 Methods………………………………………………………………………….29-32

2.1 Data collection

2.2 Data Organisation structure

2.3 Data analysis

3 Results……………………………………………………………………………..33-49

3.1 Tank Classification

3.2 Natural Fisheries productivity

3.3 Macrophytes

3.4 Poverty

4 Discussion…………………………………………………………………… ….50-54

References……………………………………………………………………………55-57

IV

Appendix

1.Average rainfall and temperature

2. Monsoon rainfall

3. Sri Lanka surface water

4. Sri Lanka’s population density distribution

5. Data clearing methodology

6. Macrophytes taxonomic identification

7. Data clearing disc* (attached to the back)

8. Statistical Analysis Result tables

V

List of figures

Figure 1. Study area and it’s geographical location (Murray 1999)…………… ………1

Figure 2. Distribution of small-scale irrigation systems in Sri Lanka ……………………6

Figure 3. Cascade system diagram (Source: Sakthivadivel 1996)……………… ……...8

Figure 4. Paddy fields…………………………………………………………… ……...9

Figure 5. Tank cover with aquatic plants…………………………………………… ….20

Figure 6. Nymphacea Lotus……………………………………………………………..21

Figure 7. Total tank distribution (%), from each tank type, in terms of seasonality

Patterns……………………………………………………………………….30

Figure 8. Seasonality and maximum water spread relationship. ………………………..31

Figure 9. Average fisheries annual production from two types of fishing: collective

fishing and pre-collective fishing at the different tanks………………………………….32

Figure 10. Collective fishing main caught species and it distribution at the different

tanks……………………………………………………………………………………...34

Figure 11. Tank cover with salvinia sp………………………………………… ……..35

Figure 12. Tank cover with Nelumbo nucifera…………………………………………..35

Figure 13. Utricularia vulgaris ………………………………………………………….35

Figure 14. Nymphacea Lotus…………………………………………………………….35

Figure 15. Mean percentage of area covered by different macrophytes within the 92

tanks…………………………………………………………………………… ………36

Figure 16. Macrophytes encroachment in tanks by type , from 92 tanks……………….37

Figure 17. Aquatic encroachment and fisheries productivity correlation from collective

fishing production………………………………………………………………………..40

Figure 18. . Aquatic encroachment and fisheries productivity correlation from pre-

collective fishing production……………………………………………………………..40

Figure 19. Effects of desilting over the macrophytes encroachment. Represent the total

number of tanks (%), by degree of rehabilitation receive if any and the percentage of tank

area covered by macrophytes…………………………………………………………….42

Figure 20. Average distance to main infrastructures from the villages allocated at the

different tanks……………………………………………………………………………44

VI

Figure 21. Distribution of land ownership opposed to paddy cultivators owners within the

different tanks……………………………………………………………………………47

Figure 22. Temporal labour (coolie) distribution at the different tanks…………………48

Figure 23. Distribution of type of houses at the different tanks. Total percentage and total

number of houses………………………………………………………… ……………49

Figure 24. Caste distribution at the different tanks……………………………… ……..50

Figure 25. Salvinia molesta physiology…………………………………..Appendix

Figure 26. Salvinia molesta in the wild …………………………………..Appendix

Figure 27. Pistia stratiotes ……………………………………………….Appendix

Figure 28. Echhornia crassipes photo ……………………………………Appendix

Figure 29. Echhornia crassipes drawing ………………………………….Appendix

Figure 30. Nelumbo nucifera flower ………………………………………Appendix

Figure 31. Nelumbo nucifera at the tank …………………………………..Appendix

Figure 32. Ceratophyllum demersum ………………………………………Appendix

Figure 33. Ceratophyllum demersum leaves ……………………………….Appendix

Figure 34. Eleocharis dulcis ………………………………………………..Appendix

Figure 35. Nymphoides indica photo ……………………………………….Appendix

Figure 36. Nymphoides indica drawing ……………………………………..Appendix

Figure 37. Utricularia vulgaris at the tank ………………………………….Appendix

Figure 38. Utricularia vulgaris physiology …………………………………Appendix

List of tables

Table 1. Land utilization within agricultural holdings…………………… ……………11

Table 2. Annual Aquaculture production…………………………………… …………15

Table 3. Tank Classification based on water seasonality……………………………….28

Table 4. List of Aquatic plants found in the field and their common names… ………38

Table 5. Uses, introduction agent and control methods from the main macrophytes in 20

tanks……………………………………………………………………………………...41

1

1. Introduction 1.1 Geography

The study has been carried out in Sri Lanka, a teardrop shape island in the Indian

Ocean. With 353 km long from North to South and 183 Km at its widest, has an area

of 66,000square Km, comparable to the size of Ireland or Tasmania (Niven et al;

1999)

Sri Lankas topography is characterised by a south central mountain range, which

reaches heights of 2524m above the sea levels (Piduratagala) and known as the Hill

country, surrounded by a coastal plain.

The island is characterised by a variety of landforms, ranging from flat erosion or

ridges, plateaux, and valleys. Sri Lanka is considered to be made up of seven major

land formed units, a coastal plain, a continental shelf, a circum-island peneplain, a

central massif, the Sabaragamuwa hills, the Gayola hills and the Elahera ridges (De

Silva, 1988).

The flat North-Central and northern

plain extends from the hill country all

the way to the northern tip of the

island, region where the study was

based, Puttalam and Kurunegala

Districts, NorthWest Province within

Dry Zone.

(Figure 1)

1.2 Climate

The island climate is tropical humid,

although a range of climatic patterns

are found on the island.

Temperature and precipitation are the

most important climatic factors of the Figure 1 . Study area and it’s geographical location (Murray 1999)

2

island (Appendix 1). In the same token the most dominant factor determining the

climatic patterns are the two monsoons, the south-west active from June through

September and the north-east active from December to February, and the related

inter-monsoonal effects (De Silva, 1988).

Due to its geographical location with respect to the central mountain rage (Hill

country), which acts as a physical barrier, the North West Province is barely affected

by both monsoons, therefore the annual mean rainfall (1270-1905mm) is considerably

lower than at the central, west, and southern parts of the island (2540-5080mm) (De

Silva, 1988).

The two main rainy seasons, directly related to the already mentioned monsoons are

the Maha season from October to March and the Yala season from April to June. The

Maha season is the most important season in terms of rainfall compare to the Yala

(Appendix 2).

From June to September the third season, or Dry season, dominates the area, in which

literally no rain falls.

1.3 Vegetation and Fauna

1.3.1. Vegetation

Of the biotic resources of Sri Lanka, the vegetation is the most outstanding in view of

its diversity, species-richness, high degree of endemism and its great economic

potential (Pemadasa, 1984).

Nearly 30% of the 3000 species of vascular plants in the island are estimated to be

exotic. Five major types of communities exist:

a) Marine vegetation. Consisting of salt marsh vegetation, mangrove vegetation,

sandy shore vegetation, sand dune vegetation (along the coast)

b) Fresh water aquatics and marsh communities.

c) Tropical wet evergreen forests.

d) Tropical semi-green forests.

e) Tropical thorn forest found in the north-western and south-western coastal

areas.(Abeywickrema, 1955)

3

1.3.2 Vegetation of the Dry zone The overall picture of the vegetation in the Arboretum reflects the physiognomy of a

Dry Zone forest. But given its regeneration from the previously degraded scrub

jungle, this forest is one of second growth or a secondary forest.

The distribution of the different vegetation types in this forest Arboretum is

controlled chiefly by the conditions of its bioclimate. IN spite of the restricted extent

of the Arboretum, these vegetation types may be broadly distinguished as follows:

a) Tropical dry (mixed) evergreen forest.

b) Moist tropical semi-evergreen forest.

c) Scrub jungle (Cramer, 1993).

1.3.3. Fauna

The fauna of Sri Lanka is of the most unusual and varied anywhere. Eighty six

mammal species include elephants, many species of deer, monkeys, leopards, sloth

bears, loris, porcupines, jackals, dungons, otters, etc.

Over 400 hundred bird species inhabit the island, of which 21 are endemic (Niven et

al, 1999).

In terms of fish fauna, Sri Lanka has a wide variety of marine tropical fish species

and freshwater inland fish species.

Between 51-55 freshwater indigenous fish species inhabit inland water bodies.

Twelve of these species are listed as food fish species (Fernando & Indrasena, 1969)

Since the first introduction of Salmo trutta in 1898, a further 19 species of true

exotics and two estuarine transplants have been added to the inland fish fauna. These

introduc tions do not include pet-fish or aquarium species. Until now no significant

detrimental effects caused by the introductions have been observed, either to the

indigenous fish fauna or the aquatic flora and other fauna. On the other hand, Sri

Lanka stands out as a classic example of a proven success of exotic finfish species,

i.e. Oreochromis mossambicus. Other introductions include: Cyprinus Carpio,

Oreochromis niloticus, Tilapia rendali, Tilapia zillii, etc. (De Silva, 1988)

4

1.4 Social-Economic Aspects

14.1 Population

The population of Sri Lanka is estimated to be 19 million ( De Silva, 1997). This

implies an average density of 278 persons per Km², which is 21st highest in the world

(Perera, and De Silva, 1997).

As in any country, the distribution is very uneven. Population is clustered extremely

densely in a few areas in the south-western and central parts of the country and spread

out much less densely in most of other parts, particularly south-eastern and northern

parts, south of the Jaffna peninsula (Appendix 4)

While the absolute size of population has been increasing, the rate of growth has been

declining. Sri Lanka’s population growth, which was as high as 3% in 1950s, has

gradually dipped close to 1.3% in the1990s (Perera and De Silva, 1997).

Population projections shows a slow increase of population, at least till the third

decade of this century to reach the 21-23 millions, to thereafter, it may remain

roughly at that level (De Silva, 1997).

1.4.2. Economy and Markets

From early historical times, Sri Lanka, was world renowned for its rich spices. The

importance of spices in the export agriculture sector diminished with the

establishment of large-scale plantations, initially of coffee followed by tea, rubber

and coconut (Figure 4). Another plant which has a key importance in the island’s

economy in the sugar.

In terms of the industrial infrastructure, Sri Lanka has a Gross Domestic Product of

26% with agriculture accounting for 24% and 50% services.

Four are the main components of the industrial sector: manufacturing, mining and

quarrying, construction and utility services, account for 15.2%, 7.8%, 2% and 1.5%

respectively (Perera and De Silva, 1997). The textile and garment sectors account

for the highest contribution in terms of output employment. Food, beverages and

tobacco processing representing 24% of output while 18% of the output is accounted

for chemicals, petroleum, plastics and other rubber products (Perera and De Silva,

1997)

5

Development of plantation agriculture and the gradual transformation of subsistence

farming to commercial farming could be considered as factors that contributed to the

expansion of internal trade in the country. The expansion of the plantation industry

necessitated the supply of its requirements; food items for workforce, tools and

implements and textiles. Most of these items had to be imported and distributed

through a network of wholesalers and retailers (Perera and De Silva, 1997)

1.4.3 Religions

Sri Lanka has a wide variety in terms of ethnic and religious groups. Although the

following information is based on the 1981 census, the distribution is still quite

representative of the actual distribution.

The main or bigger ethnic group at a 74% is the Sinhala, followed by the Sri Lanka

Tamil with 12.7% of the total population. Indian Tamils (5.5%) and Moors (7%) are

then third and forth ethnic groups.

In terms of religious groups, there is a Buddhist majority, which represent the 69.3%

of the population, followed by Hindu with 15.4% of the total population. Muslim and

Christian groups represent 7.6% each from the total (Perera and De Silva, 1997)

1.5 Inland Water Resources

In view of the topography of the island and the overall rainfall pattern, a substantial

water resource is to be expected. The natural water resources of the island take the

form of extensive river and stream systems, and the associated flood plains and

marshes. Sri Lanka does not have any natural lakes (De Silva, 1988).

1.5.1 Irrigation System

Natural reservoirs in Sri Lanka are characterized by its little abundance, although it

has 3 ha of inland water per Km² of land (almost 2% of the land surface- De Silva,

1998) [Appendix 3]. Most of this water area is a man-made legacy of ancient

irrigation systems. The purpose and determination in the construction of the irrigation

systems are depicted by the words of Parakrama Bahu the Great (1153-1186 AD):

“Let not even a drop of rain water go to the sea without benefiting the man”. In

consequence a series of watershed systems dominated the landscape, especially in the

Dry Zone.

6

Irrigation developed hand-in-hand with rice growing; rice was, and is, the staple

food. Today Sri Lanka has more than 17,000 functioning irrigation schemes

covering approximately 500,000 hectares. About 99 percent of these schemes

irrigate less than 80 hectares each and are classed as “minor” irrigation schemes. In

total, minor schemes irrigate about 150000 hectares.

Figure 2. Distribution of small-scale irrigation systems in Sri Lanka

1.5.2 Cascade Systems

A cascade system, in this case tank cascade, or a chain of tanks, is a series of small

reservoirs that are constructed at successive locations down one single common

watercourse. Thus any excess water flowing from one tank in such a chain is captured in

the next, downstream tank (Itakura et al; 1992).

Spill events, water drainage, canalisation or rainfall, are the main water sources by which

the tanks (Figure 3) progressively fill. This system has key characteristic the direct

interrelationship between all the tanks on the watershed. Therefore any disruption

occurring at any tank will affect directly or indirectly the other tanks specially those

below (Figure 3).

Due to its characteristics, this system has a high potentiality as a water system:

(Source: Cook, 1931 in Murray, 1999)

7

1) Function of re-storing and re-using drainage return-flow or recycle within the

system;

2) Buffer function, alleviating the imbalance between water demand in the command

area and the water supply from the tank, which occurs owing to the fluctuation of

both field water requirement and rainfall-runoff discharge (Itakura et al 1991).

1.5.3 Tanks

Tanks are created by the construction of earthen dams across seasonal streams (Figure 4).

Maximum water spread rages from 4-50ha, whilst 80% are 25ha or less, whilst the

average village tank is estimated to have an irrigable area of 42ha (Land Commissions

Report 1985, Murray 1999 a). Rainfall, although relatively high (>1000mm/year), is

highly variable and soils are generally shallow and porous. Many tanks only fill in above

average rainfall years. They receive most water during the main monsoon (Maha, Oct-

Jan) and irrigate some 20-30ha during the subsequent main cultivation (Maha, Oct-

March). Water levels recede gradually from Feb-Mar onwards, but may fluctuate due to

intermittent rains during the second monsoon (Yala, Apr-Jun), evaporation and

occasional draw down for agricultural purposes during the second cultivation period

(Murray, 1999 a).

An estimated 18000 tanks are clustered into 3500 to 4000 small tank cascade systems

(STC’s) with the greatest concentrations in areas of the Northwest and North Central

Provinces (DAS 1996). Over half of these tanks are operational, of which 80% are 25 ha

or less at maximal waterspread. All but the smallest, effectively private tanks, (<5ha) are

under state jurisdiction but community manage on a daily basis. Tanks are arranged

within cascading sequences of between 2-25 tanks. Tanks tends to decrease in size and

increase in seasonality with progressive movement towards the top of the watershed

(Murray, 1999)

8

Figure 3. Cascade system diagram (Source: Sakthivadivel, 1996 in Murray, 1999 a).

1.5.4 Tanks and Seasonality

Water level in tanks in the Dry zone are highly variable throughout the year. These

fluctuations define four main types of tanks: Perennial, semi-seasonal, seasonal and

highly seasonal:

9

Perennial tanks : have not dried out in living memory.

Semi-seasonal: dry one or two times every five years.

Seasonal: dry two to three time every five years.

Highly seasonal: dry every year.

1.5.5 Paddy fields

Paddy, a word of Malaysian origin, is used for both the unhusked grain of rice as well as

the leveled plot of wetland enclosed by earth bunds for the cultivation of semi aquatic

grass Oryza sativa.

Immediately below almost every tank, this principal irrigated crop, paddy is found

(Figure 4). In total, paddy is grown on nearly 600.000 ha of land. Nearly half of this total

is grown under minor and medium irrigation sys tems. Of the remaining 250,000ha under

major irrigation (>600ha) nearly 130,000ha are under the Mahaweli Development

scheme1. Straddling North Central Province is the Mahaweli H irrigation system, part of

the Mahaweli development program initiated in 1975 to relieve population pressure in the

Dry Zone to the west, which is the main location where the research was carried out

(Murray, 1999).

Figure 4. Paddy fields at the Dry Zone. Sri Lanka

1.5.6 Water Quality

Surface waters draining from the granite hills of Sri Lanka is normally clear, soft and

more or less neutral in pH. Lowland standing bodies have a higher level of dissolved

1 Largest multipurpose national development programme. Main objectives are: generation of Hydropower, settlement of landless and employed families and provision of irrigation facilities for the Dry Zone.

10

solids, conductivity and are generally alkaline. pH values varies widely, depending on the

season. Generally pH levels fell within 6-8.5, although higher values occur in the lower

tanks (Murray, 1999).

Water temperatures in tanks are highly stratified, ruled by daily and seasonal patterns.

Temperature reach 35º C in shallow paddy fields and shallow receding waters of smaller

ponds (Murray, 1999). Mean water temperatures are around 25º C.

Turbidity, characterized by high silt levels, occurs especially after heavy rains and in

smaller upper watershed tanks. Widespread encroachment of aquatic macrophytes and

degradation of the catchment areas is likely to have increased silt levels whilst causing a

net reduction and increase in the organic and inorganic nutrient load of water flowing to

lower tanks in the longer term (Murray, 1999).

High levels of pesticides are mainly used in irrigated areas. The presence of such

chemicals vary with the season, position in the cascade system and cultivation strategies.

Therefore during the dry season and at lower tanks the accumulation of pesticides is

greater. (Murray, 1999)

Most of the water quality parameters are within acceptable ranges, although water quality

decreases during the dry season.

1.6 Agriculture

Agriculture continues to be the mainstay of the national economy though it’s distribution

to GDP is in decline as the manufacturing sector expands (it’s share rising from 14.8% in

1985 to 197% in 1994- Central Bank 1998). Prior to 1997, farmers benefited from

assured markets and high production subsidies under a centrally planned economy, which

stressed self-sufficiency in food production (Weragoda 1998, in Perera et al 1997) but

stifled economic growth. These benefits along with projectionist exchange controls and

import quota restrictions were gradually abolished during two decades of progressive

economic reform, which aimed to encourage greater market orientation and production

efficiency amongst producers (Kodithuwaku 1997 in Perera et al 1997) and export

orientated economic growth (Kelegama 1999).

11

1.6.1 Agricultural land use

In the rainfed focus areas of this project, most villagers derive their primary source of

household income from farming activities. Paddy (the staple food along with fish) is the

principal irrigated crop. Dryland crops are grown under a traditional pattern of shifting

‘slash and burn’ or fixed highland cultivation, whilst vegetables and other cash crops are

also grown in smaller home-gardens. Livestock holding, already low within this

predominantly Buddhist society, are declining further due to reduced pasture availability

and mechanization of tasks formerly undertaken by draught animals (Central Bank 1998

and pers. Obs. in Perera et al 1997)

Table 1. Land utilization within agricultural holdings in Sri Lanka

(Source: Garmage, 1997, ESCAP 1997)

Type of agricultural land use Area Total (ha) Percentage

Total land area 6.5 Natural forest cover 1.5 Total area under agricultural production 3.2 100 A. Permanent cultivation 2.07 65.8 Plantation (tea, rubber, coconut) 0.94 29.4 Mixed upland crops and home-gardens 0.6 18.8 Total irrigated Land 0.6 18.8 Irrigated paddy under seasonal tanks (<80 ha) 0.23 7.4 Irrigated paddy under seasonal tanks (80-600 ha) 0.05 1.6 Irrigated paddy under major irrigation (>600 ha) 0.25 7.8 B. Shifting slash and burn 0.95 29.7

C. Pasture 0.02 0.63 D. Uncultivated cultivated area 0.092 2.9

1.7 Fisheries

The fisheries sector plays a vital role, contributing as much as 65% of the animal protein

to the Sri Lankan diet. Although the contribution of the fisheries to the Gross National

Production of the country is lower than that of the agriculture sector, fisheries play an

important role in the nutrition and socio-economics of the country. The local demand for

fish and fishery products has kept rising progressively each year, with the demand in

1998 (319.881 tons) being 3,1% more than the demand in 1997 (NARA, 2000, 1999)

12

The inland capture fishery of Sri Lanka is a lucrative commercial enterprise based on two

African cichlids, Oreochromis mossabicus and Oreochromis niloticus establish in large

perennial reservoirs of the Dry Zone (Nathaniel, 2000).

Although the marine sector dominates fish production in Sri Lanka, in rural areas, where

poverty and malnutrition prevail, the demand is for cheaper locally available freshwater

fish. The rural community in inland dry zone areas is dependent on freshwater fish for

81% of its protein requirement (Nathaniel, 2000).

Due to the lack of protein, 62% of mothers and 66% of children in rural areas suffer from

malnutrition and other diseases. On the other hand, due to the lack of food in their home

38% of children going to school in rural fishing communities do not attend to school

(Nathaniel, 2000, 1999)

1.7.1 The capture fishery

Of the 18 food fis h species introduced, the Java or Mossambique tilapia Oreochromis

mossambicus has been a resounding success, while two other cichlid species

Oreochromis niloticus and Tilapia rendalli, have established breeding populations. Two

air breathing specie, the snakeskin gourami (Trichogaster pectoralis) and the giant

gourami (Osphoronemus gourami) have establish highly localised populations, that are

high enough to support a fishery on the western coastal flood plains (Penthiyagoda,

1999).

Several non-tropical major carp species have also been introduced such as the common

carp (Cyprinus carpio), Indian carp (Catla catla, Cirrhinus mrigala and Labeo rohita)

and Chinese carp (Aristichthys nobilis, Ctenopharyngo donidella and

Hypophythalmichthys molitrix). Of these species only the common carp (Cyprinus

carpio), and rohu (Labeo rohita) have established self-sustaining populations in Sri

Lanka (Penthiyagoda, 1999). The common carp now occurs in many headwater streams

above elevations of 1500 m (Penthiyagoda, 1999). Most of the remaining species

introduced as food fish persists in small populations, which may die out in the near

future.

13

1.7.2 Indigenous fish fauna

The most abundant indigenous species in Sri Lankan reservoirs are the minor cyprinids

(<10 cm) such as Amblypharyngon melottinus, Puntius filamentosus, Puntious chola and

Puntius dorsalis, which form a substantial resource (De Silva and Sirisena, 1987;

Amarasinghe, 1994; Pet and Piet, 1993; Piet 1996).

Although these fish could gainfully be exploited without harming the existing

commercial fishery, large-scale commercial exploitation is unlikely to occur under the

existing fishery regulations, which prohibits the use of small meshed nets. However,

small quantities of these small cyprinids could also be used for the preparation of

fishmeal or dry fish production (De Silva, 1996; Amarasinghe, 1990)

Of the larger indigenous species food fish, the striped snakehead (Channa striatus ) and

eels are among the high value species. Two indigenous cyprinids P. sarana and L.

dussmeiri along with the estuarine transplant Etroplus suratensis, which has established

itself in some reservoirs presently contribute to a small-scale commercial fishery. Two

silurids, Ompok bimaculatus and Wallango attu were major constituents of the inland

fishery prior to the introduction of exotics.

Reservoirs are not suitable breeding grounds for indigenous species, since these fish

require riverine habitats for spawning (De Silva, 1983).

1.7.3 Fisheries of perennial and seasonal tanks

Stocking trials in rain-fed village tanks have demonstrated yield potential in excess of

800 Kg/ha/yr-¹ (Chakrabarty, 1983 in Murray et al 2000), though results have been

highly variable and so far no sustained adoption has been achieved. In the absence of

stocking initiatives, substantial though erratic natural production occurs in such tanks

(Murray et al, 2000)

14

Production levels2 during seasonal collective fishing are between 150-200 kg/ha for tanks

holding water for less than 6 months. Greatest variation exists in the production levels

from medium sized semi-seasonal tanks (drying intermittently), where the potential for

natural repopulation depends on seasonal hydrological linkages between tanks at the

wider cascade level. Such linkages are in turn determined by a number of factors,

principally seasonal rainfall patterns and tank rehabilitation practices. Village patterns

and tank production, which are concentrated mostly during the dry season, remain

invisible to official statistics, being used almost exclusively for local household

consumption (Murray et al, 2000).

1.7.4 Fisheries Management 3

Fish production in small tank systems appears to be of greater importance to the

livelihoods of villagers in the lowest wealth rank relative to those in the middle and upper

ranks. This is attributed to several factors. Most of the fish consumed in cascade systems

originates from large perennial reservoirs, yielding a cheap, highly available product

delivered fresh on a door-to-door basis by mobile 2-wheeler vendors (Murray, 1999 b).

By contrast, very little of the production from the seasonal tanks enters commercial

markets, due to negative consumer quality perceptions associated with such fish. Most is

used instead for local consumption.

Traditional communal fishing practises and taboos formally designed to both restrict

access and preserve stocks have become eroded along with the community-based

institutions that contributed to their enforcement. They endure in part only as a

consequence of the priority accorded to bathing rather than fishing. Direct efforts to

enhance or manage the fisheries in any of the tanks investigated were restricted to very

occasional, individually sponsored, movements of wild brood stock. Most of the fisheries

are casually exploited by a small number of farmers living around the tank . Full open-

access status is only curtailed by a residual of weakly enforceable customary rules and

2 Refers to results obtained from Anamaduwa and Giribawa regions (Murray & Little, 2000) 3 Based on the study of two cascade systems, Danduwellawe and Pahala Diuluwewa (Murray et al, 2000)

15

norms favouring other priority uses. Most fishing efforts take place during the dryer

months (June –July).

The major common rule relating to seasonal tank fisheries is a prohibition on gill, seine

or cast-net fishing during the dry season to preserve the quality of any residual water for

bathing.

In terms of fishing method, a variety of selective and non-selective methods are used. The

most common one is gill netting (2” stretched mesh size). Passive fishing is rare, with

the exception of the collective harvesting period when rows of gills nets may be left in -

situ and rechecked over a number of days, this is due to the risk of leaving value gear

unattended. Recreational fishing is often practice by children, using hook and line

(Murray, 1999).

1.7.5 Aquaculture

Freshwater fish species used at present in fish culture are the Nile tilapia (O. niloticus),

red tilapia, the common carp (Cyprinus carpio), Indian major carps (Labeo rohita,

Cirrhinus mrigala and Catla catla ), grass carp (Ctenjopharyngodon idella ), big head carp

(Aristichthys robilis), silver carp (Hypophythalmichthys molitrix), and the indigenous of

Labeo dussumberi. At present the required number of Labeo dussumberi fry for culture

purposes are obtained through artificial breeding. Culture of carnivorous species such as

snakehead is not popular in Sri Lanka due to high production cost, and slower growth rate

compared to omnivorous or phytoplanktivorous species (Nathaniel, 2000)

Table 2. Annual Aquaculture Production

Sub-Sector 1997 1998 1999

Aquaculture* 27 ( metric tons) 30 (metric tons) 31 (metric tons)

(Source: Ministry of Fisheries and Aquatic Resources Development, Sri Lanka)

*Inland sector, coastal brackish water prawn and cultured prawn production.

16

In 1995 a new policy was established by the Minister of Fisheries to support inland

fisheries activities, which result in the creation of an aquaculture development division.

In this new division the major functions are seed production, stocking of water bodies,

training of personnel in aquacultural practices, development of adaptive research,

creation of awareness of environmental aspects and transfer of technology to the private

sector.

Seed production The State will assist and provide incentives to the private sector including the

purchase of fish seed from private farmers. The government will also promote the

participation of rural communities in seed production activities to ensure self-

employment and additional income to the rural people. As a part of the new strategy, the

government has already taken steps to make the aquaculture centers at Udawalawe and

Dambulla functional. Indian major carp will be bred in these stations and the fry of these

species will be handed over to the private sector for further rearing. The estate

management in the country will be encouraged to produce fingerlings in the estate tanks

through active participation of estate workers. The necessary inputs such as fish fry,

training facilities and financial assistance will be provided by the state. Part of the plan is

also to encourage the NGOs and agricultural farmers to produce fish fingerlings on a

small scale and establish community-based fish seed production centers. All necessary

assistance will be provided by the government (Minister of Fisheries and Aquatic Resources

Development, Sri Lanka).

Stocking of water bodies

Fish seed required for the stocking programs will be purchased from the farmers.

Participation of fishers cooperatives in the production of seed in the major tanks will be

encouraged. People's participation in resource management

Considering the common property nature of the reservoirs, active individual participation

will be ensured by co-operative societies, which will be organised where they do not

already exist. Similarly, in the case of seasonal tanks, appropriate organisations will be

17

formed to involve the participation of local inhabitants in resource management (Minister

of Fisheries and Aquatic Resources Development, Sri Lanka).

Incentives

Appropriate incentives such as tax holidays, duty free imports and proportionate

reduction in lease rentals, are envisaged for the promotion of aquaculture ventures.

(Ministry of Fisheries and Aquatic Resources Development)

1.8 Macrophytes

Macrophytes are the conspicuous plants that dominate wetlands, shallow lakes, and

streams. Macroscopic flora include the aquatic angiosperms (flowering plants),

pteridophytes (ferns), and bryophytes (mosses, hornworts, and liverworts). An

aquatic plant can be defined as one that is normally found growing in association with

standing water whose level is at or above the surface of the soil. Standing water

includes ponds, shallow lakes, marshes, ditches, reservoirs, swamps, bogs, canals,

and sewage lagoons. Aquatic plants, though less frequently, also occur in flowing

water, in streams, rivers, and springs (Stern, 2000) Aquatic macrophytes play a vital role in healthy ecosystems. They serve as primary

producers of oxygen through photosynthesis, provide a substrate for algae and

shelter for many invertebrates, aid in nutrient cycling to and from the sediments, and

help stabilize river and stream banks.

Biological filtration is an increasingly popular method of sewage treatment; some

aquatic plants are being used to remove nutrients and reduce concentrations of

phosphorus and nitrogen from raw sewage or from effluent sewage treatment

facilities. Aquatic plants are also able to absorb other substances, including pollutants

such as phenols (Kaufman, 1989).

Aquatic plants supply a wide variety of wildlife with food and suitable nesting

habitats. Some, even help to control pest populations; duckweeds are known to

reduce mosquito numbers, which has the added benefit of decreasing the incidence

of certain insect-borne diseases.

18

However, humans do not always consider plants to be so beneficial. Flooding of

agricultural land is a concern for many that farm on or near a watershed and plants

can play a significant role in creating these problems. As macrophyte biomass

increases, the mean water velocity of a river decreases. If river discharge is constant,

such a reduction in velocity will raise the water level, thereby presenting the

possibility of overflowing banks or raising water tables (Kaufman, 1989).

Fishing and navigation is another concern as tall emergent plants can prevent access

for shoreline fishing. Submerged species can also spoil the gravel spawning beds of

some fish (salmonids, in particular) and high densities of photosynthesizing

macrophytes are capable of causing large fluctuations in oxygen; this can stress many

fish species. Similarly, fish mortality may ensue when photosynthesis does not exceed

respiration (under prolonged hot and cloudy conditions), thus resulting in oxygen

depletion (Kaufman, 1989).

While some aquatics deter certain disease-carrying organisms, others provide an

ideal habitat. Several human diseases are transmitted through intermediate hosts that

are either dependent upon certain macrophytes for completion of their life cycle or

inhabit stagnant water resulting from the obstruction of water-courses by vegetation.

Schistosomiasis (African sleeping sickness) is one example; the intermediate host is

an aquatic snail that lives among aquatic vegetation (Kaufman, 1989)

. 1.8.1. Macrophytes of Sri Lanka The great abundance of surface water along the whole Sri Lankan geography, mainly in

the form of man made reservoirs (tanks), toge ther with the high level of water

interchange between water bodies, makes an ideal ecosystem for the subsistence of

aquatic plants.

Sri Lanka water bodies, especially man made reservoirs, are in fact partially or totally

encroached by a wide variety of indigenous and introduced aquatic plants.

The increasing prevalence of many aquatic weeds is, in fact, the result of human impact.

The nutrient enrichment of water bodies due to the run off of fertilizers encourages

growth and multiplication of algae and aqua tic plants to such a degree as to make them

noxious weeds.

19

At present in Sri Lanka, Salvinia and Eichhornia and to a lesser extent Limnacharis

flava, are the more troublesome weeds. Salvinia covers about 12000 ha of swamp and

paddy lands, and Eichhornia about 400 ha. (Dassanayake in Junk, 1973)

The spread of aquatic plants through the different water bodies has mainly the following

impacts:

1. Aquatic weeds reduce the flow of water in irrigation and drainage channels.

2. They sometimes block gates, points of water intake, as in power generating

stations and cause flooding.

3. Dense growths of Eichhornia and Pistia are said to harbour larvae of mosquitos

including vectors of filaria.

4. In paddy fields they reduce yields by competing with the paddy for light and

nutrients.

Some of the aquatic weeds are used by the local people for various purposes. The uses

mentioned below work against their control: 1. Leaves of Limnocharis flave and

Monochria vaginalis are eaten as a pot herb by some people. 2. Flowers of Eichhornia are

used as offerings in Buddist temples, and are often locally sold outside temples. 3. Fresh

salvinia is used as packing material for fish. This practice is largely responsible for its

spread from one region to another. 4. Salvinia and other aquatic macrophytes are used for

making compost. Salvinia is comparable to cattle manure in nutrient composition and it

can be used for compost making, which may help in its control if planned properly

(Dassanayake in Junk, 1973).

18.2. Noxious water vegetation in Sri Lanka

The main types of aquatic plants found in large water bodies along Sri Lanka are found in

the form of:

Floating weeds

Eichhornia crassipes, Salvinia auriculata and Pistia stratiotes are the

three most troublesome floating weeds.

20

Emerged weeds

Typha javanica (bull-rush weed) and Limnocharis flava (water cabba

ge), are widely occurring weeds of this type in the country.

Submerged weeds

Hydrilla, Vallisneria and Utricalaria are the most common submerged

Weeds.

Bank weeds

Lagenadra ovata (Ketala) Typha javanica (Hambu)

Algae

These do not cause any serious problem in Sri Lanka, but few sporadic

cases of poisoning of cattle have occurred and the blue-green algae are

suspected to be the causal organism.

In spite of heavy expenditure and efforts of most farmers directed towards the destruction

of water hyacinth, it has not been possible to control it satisfactorily. Experience with

other aquatic weeds such as Salvinia and Pistia has also been unhappy and very costly to

farmers and to the State. Government appeals and the legal machinery have failed due to

the irresponsibility of some farmers and land owners (Junk, 1973).

Figure 5. Tank cover with aquatic plants.

21

Figure 6. Nyphacea lotus.

22

Objectives

This study had as the main aim the enhanced management of seasonal tank fisheries. In

order to achieve such an aim, two factors have been studied: bio -physical and socio-

economic.

The principal objectives are:

1.Bio-physical

1.1 A review of the present tank classification, which aimed to obtain a more accurate

and explicit tank classification with respect to the seasonality, water input and

location within the cascade system. The new classification will allow the

identification of potential aquaculture development in quick an accurate manner.

1.2 The trends in water use by the surrounding livelihoods in seasonal tanks and an

assessment of the resources flow, with respect to primary productivity and water

availability.

1.3 The impacts of macrophytes on the tanks, to assess the role of these aquatic species

in such environments and on the surrounding livelihoods with a special attention to

new introductions like salvenia.

1.4 The effects of tank rehabilitation over macrophytes encroachment, to assess it’s

viability as a control method.

2. Socio-economic

2.1 The location in the watershed with respect to different resources and distance from

important infrastructures such as schools, hospitals, etc., to assess their impact on

the role of tanks and their value in people’s livelihoods.

2.2 The assessment between geographical location and wealth, as well as social factors

such as caste.

The previous objectives will identify the level of dependence on natural resources within

the watershed and the possible social conflicts.

23

2. Methods This report has followed a wide variety of methods and techniques, due to the abundance

of different areas directly involved with the main project objective, the enhancement of

management in seasonal tanks for aquaculture. The range of areas covered includes

physical, biological, social, economic and marketing aspects. The collection of

information and the following analysis for each area required different methods to

achieve accurate and reliable results.

Three main tasks have been carried out during the project, covering the areas already

mentioned.

2.1 Data collection

The first task or data collection has been mainly carried out in the field by a group of

researchers, during the past 2 years. Collection of primary and secondary data from the

tanks and the surrounded livelihoods has been the main aim of this research group4.

In addition to the collection of primary data by the already mentioned researchers, 3 to 4

days a week over two months were spent in the field collecting data in order to become

familiar with the methodology used as well as the study areas and to assess the accuracy

of the techniques carried out in the field. Other additional data related to macrophytes

was also collected during the course of the two 2 months.

2.1.1 Primary data

Physical primary data has been collected, in order to configure the status and trends of the

different physical factors related to tank hydrology. This task was mainly carried out by a

research assistant, having as main task water quality parameters data collection and

analysis, which included pH water analysis, dissolved oxygen analysis, suspended solids

analysis and evaporation rate analysis. In addition water level measurements from all

tanks, and weekly measurements from key tanks were collected.

4 Research group: PHd, student: Francis Murray, field staff: Priyantha Jayakody, Yasantha Nawarathne, Bandara Samarakoon.

24

Data collection was carried out in the field on key villages and related tanks. The

methodology used is often known as participatory field work, where a wide variety of

tools have been developed, employed systematically in what are known as Participatory

Rural Appraisals and Rapid Rural Appraisal, the major distinction lying with the degree

of farmer participation. The variety of tools used in this project are listed in Box 1

(Murray & Little, 2000)

The major uses of water bodies as well as the key constraints to the introduction of

aquaculture into village tanks were identified in community meetings and ranked and

scored in order of priority by farmers. To asses the wider impacts of water and land

management practices, appraisal was extended to the cascade level using individual farm

and catchment walks and key informant interviews. Farmers were questioned about

historic trends in water availability, tank system operation, maintenance and management

(Murray, 1999 b).

Box 1: Participatory Rural Appraisal Tools used in the project field research (after Townsley, 1996 in Murray & Little, 2000) Secondary data sources: Used as in conventional research Semi-Structure Interviews: Instead of a formal questionnaire, interviews use a checklist of questions related to each topic of interest. This is a flexible method allowing for the follow up of interesting topics arising during the interview. Interviews can be conducted with Key informants (people with specialist knowledge about a topic or third parties), with individuals or groups. Ranking and scoring: Issues or items are placed in order of importance (ranking) or allocated a proportion of a limited number of points (scoring). Used to identified the priorities of a community when carried out with individuals. Wealth ranking: Used to investigated local perceptions of wealth grouping within the community. Parameters used in the classification identified by villagers, thus revealing local indicators and criteria of wealth. Diagrams and maps: Used to simplified and present complex information in a easy to understand format. Often used to stimulate the interest of villagers and increase their participation. Resource flow diagrams: To show the flow or resources (e.g. water, crops, animals, plant/animal residues, agro-chemicals, money) between the different components of a system. Watershed maps: To show the ownership of land holdings and waterbodies within a watershed. Seasonal diagrams: To show patterns of rainfall, food availability, workload, credit etc.. over a year. Venn diagrams : To show the relationships and connections between different individuals institutions in a community. Social maps: To show distribution of all village households along with demographic and resource ownershi details (i.e. gender balance, caste , wealth status, literacy, land ownership etc.) Activity charts: To chart the activities carried out by individuals or groups within a fixed time period

25

2.1.3. Assessment of importance of macrophytes

This particular section of the study focused on the impacts of macrophytes on the

surveyed tanks and the surrounding livelihoods, to compliment and add a greater

accuracy to the data already collected by the research group. Two main tasks were carried

out:

1) Collection of primary data, through a survey questionnaire, based on six main

questions (Box 2), and carried out in three representative cascade systems using as key

informants, mainly farmers and fishermen from the surrounding villages.

2) Taxonomic identification of the main species found at the tanks. Consultation of the

main botanical local literature sources, mainly at Peradeniya University library

(Kandy, Sri Lanka), in order to classify the species found in the field and their main

characteristics (Appendix Number 6).

The level of encroachment of aquatic macrophites was estimated for the 92 tanks in terms

of percentage area covered and differentiating the main aquatic plant species present

(Ollu/Nelum, salvinia, water hyacinth, submerged plants and others). Respondents were

asked to estimate cover for the last two main monsoon seasons (Maha and Yala) over

the last two years.

New methods for area estimation and macrophytes distributions were tried. Such

methodology was based on the creation of a standard model for area estimation, which

will give an approximate estimation of the area covered by macrophytes. But due to the

lack of time and also resources such methodology had to be abandoned.

Box 2: Macrophytes questionnaire 1) Which are the main macrophytes in the tank? 2) When did the different macrophytes first appear? 3) Do they have the impacts on fishing, bathing or irrigation? If yes, which ones? 4) How did the infestation start? 5) Has any increase in mosquitoes occurred with the increase of macrophytes? 6) Is there any control method, presently used? 7) Are the macrophytes used for any purpose?, if yes, which ones?

26

2.2. Data organization structure As a result of the work mainly done by the research group and the extra data collected

during the length of the study (2 months) in the field, a series of spread sheets were

created, which contained a wide variety of data. Seven spreadsheets, which mainly

covered hydrological aspects, water management and uses, livestock characteristics,

fisheries aspects, social and economic issues, from the 92 tanks surveyed and the related

villages surrounding the tanks. A special distinction has been made in the data collected

during the two main seasons (Maha and Yala).

Due to the extension of the data recorded and to the different personnel involved with the

data entry, data clearing was needed, to tidy up the spreadsheets and facilitate the

understanding and handling of the information collected. The output from such data

clearance and the differences from the original raw data can be observed in the Appendix

7 (disc attached). Also the methodology followed during the data clearing, which

involved between others, grouping, reclassification, etc. is summarized in Appendix 5.

2.3. Data Analysis

Once the data collected was cleared and tidied up, a selection of the relevant data from

the spreadsheet was carried out, mainly spotting the information necessary to reach the

proposed objectives (Introduction, section 1.9).

Analysis of selected data was carried out using two main statistical packages, Excell’98

and SPSS version 9. Descriptive statistical methods were the principal type of analysis

used, aiming to obtained a clear view of the situation, task, which have not been done

before. The use of simple descriptive methods was chosen, because: no data analysis was

done previously, therefore demonstration of the main hypothesis was needed beforehand,

to later carry on with more complex methods.

Following the use of descriptive statistical methods. More advanced statistical analysis,

using mostly Chi square tests on count and univariate and multivariate analysis of

variance (ANOVA) with or without interaction depending on the data analyzed were

used. Normality and Constance variance tests were also run to assure the analysis results

reliability and it accuracy. No Post hoc analysis was carried because the amount of data

used was insufficient to obtain reliable results.

27

3. Results

The following results covered a wide range of subjects all related to the success of fish

culture in different tanks, therefore most of the results have a common denominator,

which is the tank classification, based mainly on water-input and seasonality factors.

3.1 Tank classification

The cascade systems vary in complexity, although two main configurations are presently

used to classify cascade systems (Linear and Branch5), still there is no clear classification

which distinguishes accurately the main characteristics of each tank in the system.

So far the main system currently used to classify tanks is based on the tank seasonality

(Drying frequency6), although this classification (Table 3) describes in a concise manner

the main limiting factor (water availability) for aquaculture development, it still lacks of

information related to geographical location and size.

Murray, (1999 a), came up with a new system to classify the different tanks based on

their position within the cascade system and their water input and retention. This system

distinguishes three main types:

Radial tanks: Mostly at the top of the cascade with its catchment area as only

source of water.

Axial 1: Receives water from 1 or more Radial tanks (intermediate location)

Axial 2: Receives water from axial 1 tanks and radial (Bottom of the cascade)

Together, the mentioned classifications give a general idea about the tank characteristics

but based on the field experience still there are still no clear links between these two

classifications.

5 Linear cascade system: Series of tanks linearly configure in the axis Branch cascade system: A main axial configuration fed by multiple outer tanks 6 Dry tank: when water level is not enough to sustain fish life.

28

Tank Type Drying Frequency

Perennial Have not dried in living memory

Semi-seasonal Dries one or two times every 5 years

Seasonal Dries two or three times every 5 years

Highly seasonal Dries every year

Using the above classification systems as main source, a new classification has been

created which will allow identification of almost any tank characteristics by just looking

at their location in the cascade and their relative size.

Using Murray, (1999), classification as the main coding system, few adjustments and

inclusions were made based on the data analysis (Figures 7,8) and field observations.

As result four main tanks are found in any cascade system:

Radial : Small (generally <4.8 ha), mostly highly seasonal tank, generally at the top of

the cascade, with its catchment as only source of water. Does not receive water from any

other tank.

Axial 1a: Small (<4.8 ha) and highly seasonal, which receives water from only one

radial tank.

Axial 1: Receives water from 2 or more radial tanks, seasonally variable, if >4.90 ha

is highly seasonal or seasonal.

Axial 2: Receives water from one Axial 1 tank and 1 or more radial tanks, mainly

perennial and semi-seasonal.

Axial 3: Large tanks, which receives water from 2 or more Axial 1 tanks, 1 or more

Axial 2 tanks and any radial tanks, mainly perennial, rarely semi-seasonal.

The graphical explanation for such a new classification is backed up by a series of

correlations run between tank seasonality, water input and maximum water spread

(Figure 7,8).

Table 3. Tank Classification based on water availability

29

Looking at the tank distribution (Figure 7), it can be observed that the amount of highly

seasonal radial tanks (89.4% of all the radial tanks (figure 8), followed by 7.2% seasonal

(Figure 8). Therefore except for literally 10% of the total radial tanks (57), an assumption

has been made which describes radial tanks as mostly highly seasonal (dry every year).

In terms of “Axial 1a” tanks, the relation with seasonality is even clearer where 100% of

all of them are highly seasonal (Figures 7,8).

On the other hand, the next tank type, Axial 1 tanks, which are generally located at the

middle of the cascade system, present a wider variability in terms of seasonality.

In order to get an accurate estimation of Axial 1 tank characteristics from just looking at

the map; the size factor is going to be crucial. A supplementary correlation between size

and seasonality has been made (Figure 8), this correlation gives as a result the close

association between seasonal tanks (highly seasonal and seasonal) and size, which are all

smaller than 4.9 hectares. Therefore after identifying an Axial 1 tank from it location and

water input (receives water from 2 or more radial tanks), if the tank is smaller than 4.9, it

is going to be a highly seasonal or seasonal tank, if it is bigger it would be perennial or

semi-seasonal and these represent 70 % of the total Axial 1 tanks (Figure 7).

30

Figure 7. Total tank distribution (%), from each tank type, in terms of seasonality Patterns (HS:highly seasonal, SS: semi-seasonal, P: perennial, S:seasonal). Using chi-square a significant relationship between tank type and seasonality was shown

(P<0.05) (Table 7, Appendix 8), where tank types tend to have particular water

availability characteristics.

Going downstream in the cascade system, tanks are getting bigger in size and less

seasonal; the next type of tank, Axial 2 are mainly perennial (57.14%), followed by 28.5

% semi-seasona l, and the rest (14.2%) are highly seasonal tanks, which are smaller than

4.9 hectares.

Finally and at the bottom of the cascade, generally the biggest tanks in the cascade (>10

ha) (Figure 8), the Axial 3 tanks are mostly perennial (81.7%), although some of them are

semi-seasonal (18.18%).

The presented classification is able to define clearly the tank characteristics by just

looking at the map. Still semi-seasonal tanks are not clearly defined, but in terms of

highly seasonal, seasonal and perennial tanks the relationship with the water input

classification and location is quite accurate.

Correlation between water input and seasonality

0.0

20.0

40.0

60.0

80.0

100.0

Axial 1a Radial Axial 1 Axial 2 Axilal 3

Tank Type

Tan

k ab

un

dan

ce (%

)

HSSSPS

31

Figure 8. Seasonality and maximum water spread relationship ( HS:highly seasonal, SS: semi-

seasonal, P: perennial, S:seasonal. n = 92). The relationship between maximum water spread and water seasonality is significant

(P<0.05) (Table 8, Appendix 8), where side of the maximum water spread has particular

water availability characteristics.

3.2 Natural fisheries productivity 3.2.1 Natural production by tank type Two main types of fishing take place in the cascade systems surveyed:

1) Collective fishing, which takes place during the dry season once the tanks reach a

minimum water level, where the fish habitat is reduced to shallow waters, making

them more vulnerable and therefore increasing the fishing catch. This activity is a

community activity, in which the majority of the village people participate; even the

non-participants receive a small amount of the total catch.

Seasonality and maximum water spread relationship

0

10

20

30

40

< 2.5 2.5 < 5 5 < 10 >10

Maximum water spread (ha)

Nu

mb

er o

f ta

nks

PSSSHS

32

2) Pre-collective fishing, defined as regular fishing act ivity, which takes place year

round, mainly by fishermen and children, often for recreational purposes

Although some restocking has been done mainly in seasonal tanks, the majority of the

tanks surveyed rely on it’s natural production.

The fisheries production data obtained from the different tanks during the year 2000, are

a reflection of the water availability and the fishing effort, which are the main limiting

factors. Although the data source (village fishermen recalls), is not the most accurate

source, such data has been cross checked with other related data like species catch, giving

an acceptable general idea about the tank production (Figure 9).

Collective fishing (Figure 9) is the main method for fish harvest, compared to traditional

fishing (pre-collective fishing).

Figure 9. Average fisheries annual production from two types of fishing: collective fishing and pre-collective fishing at the different tanks. Clear differences (P<0.05) in production can be observed between the two types of

fishing practice, as well as at the different types of tanks (P<0.05) where the production

Average fisheries annual production of fish from tanks by category

0.050.0

100.0

150.0

200.0

250.0

300.0

Radial Axial 1a Axial 1 Axial 2 Axial 3

Tank type

Ann

ual P

rodu

ctio

n (K

g/ha

)

Fisheries Production from collective fishing (kg/ha)Fisheries Production from pre-collective fishing (kg/ha)

33

results are quite significant (Table 9, Appendix 8). On the other hand the interaction

between fish type and tank type was not significant (P=0.058).

Fisheries production from collective fishing at the different tanks is greater in the Axial 1

tanks, although the unusual total drainage of a big tank has to be mentioned, which

produced a catch of 3000 kilos. Apart from Axial 1, the radial tanks have an average of

64.4 kilos per hectare, followed by perennial tanks with 47.9 kilos per hectare.

In terms of pre-collective fishing, Axial 1 tanks are the more productive (32.6 kg/ha),

followed by axial 1a (20.5 kg/ha) tanks. Looking at the production in perennials tanks

(4.94 Kg/ha) an obvious issue that can be raised is the size factor, the bigger the tank, the

deeper, therefore the probabilities of catching fish decrease.

Looking closely to the fisheries production, 5 main species are fished, two types of

tilapia7 , climbing perch, snakehead and small indigenous species.

Tilapia and snakehead are the species mostly present in all tanks, representing

approximately between 50-60 and 30-40 percent of the total catch in each tank

respectively (Figure 10). Also present in all the tanks, although in smaller percentage, the

small indigenous species, appear to be the third more abundant prey (between 3-8%,

increasing to a 21% in the radial tanks).

On the other hand, climbing perch, although quite often caught, appear to be restricted to

mainly Axial 1 and 3 tanks (2.5 and 1.25 % respectively).

Due to the unavailability of data mainly from radial and Axial 1a tanks the above results

are subject to discussion and further study. For the same reason, no analysis have been

carried out over pre-collective fishing, from which the data was insufficient to generate

acceptable results.

7 Due to the informant’s inability to clearly identified Oreochromis. mossambicus from Oreochromis niloticus, no distinction has been made between them.

SIS:

34

Figure 10. Collective fishing main caught species and it distribution at the different tanks. (SIS: Indigenous Species) No significant interaction (P=0.7) between tank type and fish species distribution has

been found (Table 10, Appendix 8), all the tanks tend to have the same types of fish

species. Also no clear difference (P=0.931) has been found between the different tank

types, but significant differences (P<0.05) can be observed in terms of species abundance

within every tank (Table 10, Appendix 8).

3.3 Macrophytes Macrophytes are without any doubt an important aspect in the tank environment, mainly

due to their presence in nearly all the cascade systems.

Although the aquatic plant diversity in such tanks is quite broad, 4 main aquatic plants

are more abundant and are the ones with more interaction with the environment and the

surrounding livelihoods. Such species are: Nymphacea lotus and Nelumbo nucifera

(figure 14-12) locally known as Ollu and Nelum respectively, Salvinia molesta ,

Catch species distribution from collective fishing

0.0020.0040.0060.0080.00

100.00

Radial A1 A2 A3

Tank type

Tot

al C

atch

(%)

SISSnakeheadClimbing perchTilapia sp.

35

commonly known as salvinia (Figure 11), Utricularia vulgaris and Ceratophyllum

demersus locally known as parsy and veru (Figure 13).

Figure 11. Tank cover with salvinia sp. Figure 12. Tank cover with Nelumbo nucifera

Figure 13. Utricularia vulgaris Figure 14. Nymphacea lotus.

36

On average from the 92 tanks surveyed, Ollu and Nelum (Nymphacea lotus and Nelumbo

nucifera) are the most dominant species present, covering on average of 26.85 % of the

tank area (figure 15), after those species the emergent grasses cover in average a 10 % of

the tank total area, followed by salvinia (3.69%). The water hyacinth (Eichhornia

crassipes) although quite wide spread in other parts of the country, can barely seen in the

surveyed tanks covering only 1.22% of the total tank area. Other species, cover only

0.63% of the total area.

Figure 15. Mean percentage of area covered by different macrophytes within the 92 tanks. Significant differences (P<0.05) between groups of different macrophytes species were

observed in terms of abundance and distribution (Table 11, Appendix 8), where

Ollu/nelum are the most abundant species (Figure 15).

Percentage of water cover by specific macrophytes

0.63

10.06

1.223.69

26.85

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

Olu / nelum Salvenia Hyacinth Emergentgrasses

OtherSpecies

Main macrophytes present at the tanks

Per

cent

age

of w

ater

are

a co

vere

d

37

Water availability and physical conditions in the different tanks appear to determine the

presence and abundance of the already mentioned aquatic plants; therefore each tank has

a characteristic encroachment (Figure 16).

In terms of Ollu and Nelum (Nymphacea lotus and Nelumbo nucifera) encroachment has

a greater presence in the Axial 1a tanks covering the 52.8 % of the total tank area, also

close to 50 %, in the Axial 3 tanks these species are quite common (40.5%). In the Axial2

and radial tanks the encroachment of such species is reduced to 32.5 and 26.5 %

respectively, followed by axial 1with 20% encroachment of Ollu and Nelum.

The second more abundant aquatic plant group are the emergent grasses, which covered

17.8 % of the Axial 1a tank total area, followed by the Axial 3 tanks with 13,3%

encroachment, which decreased in the Axial 2, radial and Axial 1 tanks.

On the other hand, although not present in all the tanks, salvinia encroachment is quite

high in the Axial 3 and Axial 2 tanks (13.8 and 9.5 %).

Figure 16. Macrophyte encroachment in tanks by type, from 92 tanks.

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

Radial Axial 1a Axial 1 Axial 2 Axial 3

Tank Type

Mea

n p

erce

nta

ge

of

wat

er a

rea

cove

red

Olu / nelum Salvenia Hyacinth Emergent grassesOther Species

38

Significant interaction (P<0.05) has been found between tank type and macrophytes

species (Table 12, Appendix 8), where species presence varies depending on tank type.

Also differences (P<0.05) in terms of macrophytes abundance within the tank can be

observed, as well as (P<0.05) the total area covered by macrophytes in the different tank

types (Table 12, Appendix 8).

The above results are based on data taken from the field where visual estimation of the

total and species encroachment was carried out in each tank. No other method was used

to estimate tank encroachment, and due to the methods accuracy the results are not as

accurate as they could be, if applying for instance, aerial photography analysis systems.

In order to obtain more specific status data macrophytes encroachment and its impacts on

the tank and surrounding villages, a questionnaire was carried out.

From such questionnaire and collection of specimens plus later taxonomic identification,

11 species were identified as the main species at the tanks surveyed (26) from three

different cascade systems. The species below can be classified in 4 groups: a) rooted, b)

floating, c) submerged and d) aquatic grasses.

The taxonomic characteristics of each specie found in the field are indicated below

(Table 5), plus some general information in Appendix 6.

Table 4. List of Aquatic plants found in the field and their common names

B o t a n i c a l n a m e L o c a l n a m eA p o n o g e t u m c r i s p u s K e k e t i aC e r a t o p h y l l u m d e m e r s u m V e r uE i c h h o r n i a c r a s s i p e s J a p a n j a p a r aI s e h e g l o b o s a Batade l l aN e l u m b o n u c i f e r a N e l u mN y m p h o i d e s i n d i c a C o m o d uN y m p h a c e a l o t u s Ol luN y m p h a c e a s t e l l a t a M a n n e lSa lv in ia au r i cu la ta S a l v i n i aUtr icu la r ia vu lgar is P a r s iEleochar i s duc i s B o r u p a n

39

Many other species were seen at the tanks visited, but because of relatively little

abundance and little impact over the communities around the tanks, were not included in

the survey. As a result from the survey a few common main impacts were identified:

Obstruction for fishing, bathing and irrigation and reduction of tank capacity.

On the other hand, these macrophytes supply the livelihood with sources of food for man

as well as for livestock, medicine and decoration, besides other uses. A common

denominator between all the tanks surveyed is the fact that no permanent control method

is applied in order to manage the macrophytes infestation, just temporal clearance for

bathing and fishing. Such control methods were mainly manual removal of macrophytes

by villagers, normally in a collective effort. More detailed information about the survey

results is given in Table 5

3.4.1. Production and water tank area cover with macrophytes The direct impacts of macrophytes infestation on fisheries production needed to be

assessed (Figure 17,18). The interaction between those two factors is crucial for fish

production. In the study area a slight correlation can be observed between the fisheries

production and macrophytes infestation, but such a correlation is not enough to strictly

relate fish production to macrophytes infestation levels. The relationship is very similar

between the fisheries production from both pre and collective fishing.

40

Figure 17 . Aquatic encroachment and fisheries productivity correlation from pre-collective fishing production.

Figure 18. Aquatic encroachment and fisheries productivity correlation from collective fishing production.

Tank product ion and macrophytes encroachment (co l lec t ive f ish ing)

y = -1 .374x + 132 .64R 2 = 0 .392

0.0050.00

100.00150.00200.00250.00300.00

0 2 0 40 6 0 8 0 1 0 0

Aquat ic weed sur face a rea covered (%)

Fis

h ha

rves

t

(Kg/

ha/y

ear)

Fisheries tank production and aquatic encroachment correlation (Pre-Collective fishing)

y = -1,147x + 85,698R2 = 0,3676

0,00

50,00

100,00

150,00

200,00

250,00

0 20 40 60 80 100Aquatic weed surface area covered(%)

Fish

har

vest

(K

g/ha

)

41

Table 5. Uses, impacts, introduction agent and control methods from the main macrophytes in 20 tanks Botanical Name Common

Name Total Presence in Tanks (%)

Uses Impacts Introduction agent

Mosquitoes increase

Control Method

Floating macrophytes

Salvenia molesta and auriculate

Salvenia 46 No uses Obstruction for fishing, bathing and

irrigation, reduction of tank capacity

Fishing nets, spill events

No Irregular partial removal, limited

to bathing fishing areas.

Eichhornia crassipes Water hyacinth 23 Livestoc k food Obstruction for fishing, bathing, reduction of tank

capacity

Livestock No Irregular partial removal, limited

to bathing fishing areas.

Rooting macrophytes

Nelumbo nucifera Nelum or water lilies

62 Decoration (flower), food (Seeds and

stems)

Difficult to remove due stem's spines

(fishing), reduction of tank capacity

Livestock, Man No Irregular partial removal, limited

to bathing fishing areas.

Nymphacea stellata & Nymphoides indica

Mannel & Comodu

62 Food (roots), medicine

Minimal impacts Livestock, Man No No

Nymphacea Lotus Ollu 92 Decoration (flower), Food source (Seeds,

roots and stems), Medicine for diabetes

(seed)

Obstruction for fishing and bathing. Reduction of tank

capacity

Livestock, Man No Irregular partial removal, limited

to bathing fishing areas.

Aponogetum crispus Keketia 92 Food (roots & flower), Minimal impacts Always been present

No No

Diya Simbula 23 No uses Minimal impacts No

Grass macrophytes

Eleocharis dulcis Borupan 55 Carpet material Minimal impacts Livestock No No

Isehne globosa Batadella 60 No uses Obstruction for fishing (Gill netting).

Fishing No Irregular partial removal, limited

to bathing fishing areas.

Submerged Macrophytes

Ceratophyllum demersum

Utricularia Vulgaris

Veru

Parsi

75 No uses Obstruction for fishing and bathing and blocks sluice

Fishing, spills No Irregular partial removal, limited

to bathing fishing areas.

43

3.4.2. Rehabilitation One of the control methods used in tanks to eradicate or control macrophyte infestation is

tank rehabilitation, not only with the purpose of eradicating the aquatic plants, but also to

increase tank capacity.

The major type of rehabilitation used is desilting the tank. A series of tanks in the

surveyed area have undergo treatment. The result is the partial eradication of the

macrophytes infestation (Figure 19), although the effect seems to be temporary rarely

lasting more than 3 years.

Of the tanks which have been fully desilted, 90% have an encroachment level below 31

percent, of which 63.3% have been desilted in the past 3 years. On the other hand 60% of

the tanks partially desilted had an encroachment below 31 %, of which 46% were desilted

in the past 3 years.

In contrast those tanks in which no desilting has taken place, show a diverse

encroachment level, mostly high.

Figure 19.Effects of desilting over the macrophytes encroachment. A significant difference (P<0.05) has been found between the percentage of area covered and the degree of desiltation to which tanks were exposed to (Table 13, Appendix 8), although data available was based on a small number of cases. * This test may not be valid because 4 cells (44.4%) have expected count less than 5 (Table 13, Appendix 8), but looking at the plot (Figure 19) appears a clear difference in percentage within different rehabilitation degrees

Impacts of Desiltation over the macrophytes

0%

20%

40%

60%

80%

100%

Full Partial None

Degree of rehabilitation

To

tal p

erce

nta

ge

of

Tan

ks s

urv

ey

61-10031-60<31

Percentage of tank area cover by macrophytes

44

3.4 Poverty The definition of poverty is a very wide concept, which varies within the different

countries, cultures, villages, etc. In order to target those groups in the project area

context, a few factors or poverty indicators have been looked at according to the main

economic and social values found at the project area.

A series of factor indicators of wealth, were looked at:

a) Isolation, or distance from main infrastructures, like main road, schools, hospitals,

etc.

b) Ownership, amount and types of land owned (ex: paddy land, etc.)

c) Labour the type of labour in terms of benefits obtained and the durability.

d) Housing characteristics, the type of house is a clear sign of economic status.

e) Caste characteristics, there is a common association of low cast with poverty due to

the their rights limitations within the community.

The above factors have been used to try to locate such groups within the cascade system

and establish whether a poverty-location relationship can be found in at the project area.

3.4.1 Isolation

The more isolated villages are from main confounding infrastructure the less accessible

are basic needs such as food sources, medicines, clothes etc, as well as schools and

hospitals. Using the tank classification proposed in this thesis and some basic

infrastructures (main road, schools and hospitals) a location-poverty relationship was

investigated at (Figure 20).

No tangible relationship has been observed, since all main infrastructures tends to be

within the same range of distance from the different tank types (1 to 2-km difference).

45

Figure 20. Average distance to main infrastructures from the villages allocated at the different tanks.

No significance interaction (P=0.650) has been found between distance from

infrastructure and tank type (P=0.701)(Table 14, Appendix 8), where the distance is

similar from all the different tanks. On the other hand, significant differences (P<0.05)

were observed in the distance from the tanks to the different infrastructures (Table 14,

Appendix 8)

3.4.2 Ownership

Ownership8 of land, as well as the area size owned,area is a clear indicator of wealth,

giving the owner a stable source of food or economic profits. The more cultivated land

the greater the availability and variability of outputs. Lower in the watershed

8 Command area owner: ownership of land in general terms. Paddy local cultivators: ownership of paddy land.

Average distance to various types of infrastructure from the different tanks

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

MetropolitanRoad

Primary School SecondarySchool

Hospital

Dis

tan

ce (k

m)

RadialA1aA1A2A3

46

overpopulation is a common characteristic, new generations tend to settle upper in the

watershed, where there are less people, but the land is mostly privately owned (i.e.

Temples). Land type is an important indicator, for instance due to the high rice demand,

the ownership of paddy land gives a greater of wealth.

In this case a clear relationship can be observed between ownership and tank type (Figure

21).

As tank seasonality increased as well as the position in the watershed (towards the top),

(i.e: Radial and Axial 1 tanks), the size of land owned increased, whereas for larger

seasonal tank further down the cascade the area of land owned is smaller.

Figure 21. Distribution of land ownership opposed to paddy cultivators owners within

the different tanks.

A significant difference (P<0.05) was found between tank type and type of ownership

and command area owners (Table 15, Appendix 8)

Command area owners and local paddy cultivators at the differents tanks

0

20

40

60

80

100

120

Radial A1 A2 A3

Nu

mb

er o

f h

ou

seh

old

s

Command area ownersper haLocal paddy cultivators

47

3.4.3 Labour

Another source of economic stability is labour type, specially, in terms of sustainability,

whether is long term of seasonal. The reliability of seasonal jobs is an indicator of

economy stability. In the area project area such labour is known as “coolie labour”,

mainly consists of people who leave the village during the day to work in part-time jobs

in neighboring villages. Such labour can be observed (Figure 21) to increase as the

seasonality of the tanks increases, going from a 20% of the total population in Axial 1a to

5.6% in Axial 3 tanks and nearly zero in the Axial 2 tanks.

3.4.4 Housing Three types of housing characterized the villages in the study area. The main

characteristic was the house quality in terms of durability. Temporary houses, mainly

made of dry mud and palm roofs, are quite vulnerable to weather damages. Semi-

permanent houses, made of more durable materials (bricks), are less vulnerable to the

weather. Thirdly, permanent houses generally made of brick or concrete with stable roofs

made of tiles, are the last susceptible to damage.

This factor clearly is wealth indicator, where poverty is more common in villages where

more less durable houses are present.

In the project area 45% of the total households near radial tanks have temporary houses

(Figure 23), although over a 35% are permanent houses, it can be observed that

temporary houses increase towards the more seasonal tanks higher in the cascade system,

where at the Axial 2 the temporary houses represented 20% of the total houses, going up

45% at the radial tanks. Due to the higher population and social diversity, the percentage

of temporary around Axial 3 tanks houses is quite high (32%), but main house type is

permanent (68%).

48

Figure 22. Temporary labour distribution by category of tank. The importance of temporary labour (P<0.05) has been found to vary with tank category (Figure 22). 3.4.5 Caste Sri Lankan society has quite strong traditional values. Part of these values is the division

of society into different groups or castes, which are directly related with occupation. A

hierarchy based on rights and priorities define low and high casts. A possible

relationship between castes and residence near tanks has been investigated (Figure 23).

No clear relationship was observed. However, although the absence of lower castes at the

Axial 2 and 3 tanks and a decrease in the proportion of people in the farmer caste at the

radial and Axial 1a tanks was noted.

Temporary labour from living around different tanks

20

13.60

7.14 5.67

0.1505

10152025

A1a A1 Radial A3 A2

Tank Type

Per

cent

age

of th

e to

tal p

opul

atio

n

49

Figure 23. Distribution of type houses at the different tanks. Total percentage and total number of houses. A difference (P<0.05) between tank types and housing distribution can be observed

(Table 17, Appendix 8), as well as house type abundance for each tank type (P<0.05), but

no significant interaction (P=0.5) is found between tank type and housing in general

terms. Although some differences can be appreciated they are not statistically significant

(Figure 23).

Housing characteristics at the differents tanks

0%10%20%30%40%50%60%70%80%90%

100%

Radial A1a A1 A2 A3

Tank Types

To

tal P

erce

nta

ng

e o

f

ho

use

ho

lds

Perm Hses (No HH)

S Perm Hses (No HH)Temp Hses (No HH)

50

Figure 24. Caste9distribution at the different tanks. The cast classification given at the, side of graph is in hierarchy order from top to bot tom, being the higher cast. A significant interaction (P<0.05) is found between tank type and caste, variability

between the different tank types and the distribution of caste within each tank is also

significant (P<0.05)(Table 18, Appendix 8). Also abundance of the different caste within

the different tanks is significant (P<0.05).

9 Casts: Gobi= farmers (a, b, c, depending on the type of culture), Kumbara= Potters, Durai= horn players and supply carriers.

Caste and watershed position relationship

0

10

20

30

40

50

Radial A1a A1 A2 A3

Tank type

Ab

un

dan

ce (%

)

Govi AGovi BGovi CGoldsmithKumbaraDuraiGypsy

51

4. Discussion Aquaculture development in developing countries is a task that differs greatly from that

in western countries. This is mainly due to a series of economic and cultural factors. The

success of such enterprise in developing countries requires overall study of socio -

economic aspects as well as biological and cultural ones. Although no aquaculture

practices take place in the project area, the aim of the broader project is to develop

approaches to aquaculture based on seasonal tanks.

Many projects and studies have been carried out aiming to improve aquaculture

development in needy areas such as the Dry Zone, but most of them have failed to obtain

positive or sustainable results. The main reason for such failures is the limited scope

which those studies have focussed on. Most of such projects have looked at specific

aspects, for instance, biological aspects, socio-economic aspects, etc, but they failed to

interrelate the different aspects to obtain an overall view.

This study had as an main aim the interrelation of the most relevant aspects for future

sustainable development of aquaculture in the study area. Therefore a wide scope of

aspects has been looked at, covering physical, biological, social and economic conditions.

4.1 Physical aspects An understanding of the physical aspects is necessary since they are limiting factors.

Once such aspects have been identified and classified, a more precise view of resource

use is obtained. In the study area the potential for aquaculture is clearly identified with the use of the

tanks or man made reservoirs as a main resource. Due to the wide variety of tanks with

respect to location, water catchment and seasonality a base classification was needed

(Results 3.1). This classification is the main reference point for further studies of other

aspects. Such classification enables the identification of potential fish culture based on its

main characteristics. Such characteristics are well described by this new classification,

covering most of the cases. The Axial 1 tanks are the only tank type, which due to their

variability in tank size, seasonality and location are not clearly defined by such

classification.

52

Other constraints found, is the location variability of the radial tanks within the cascade

system. Although most of them are located at the top of the cascade system, a series of

radial tanks also appear close to the Axial 2 and 3 tanks, which are at the bottom of the

cascade. Either way radial tanks are situated on the outskirts of the cascade system.

New tanks keep being discovered on nearly a daily basis. These tanks mostly fit on the

new classification but as new ones are discovered, the variability characteristics

increases, therefore although the classification accurately describes known tanks a review

will be needed in the future.

The data on which the new classification is based on, although it gives an acceptable

description of tanks characteristics, can be criticized for the use of not very accurate

methods in terms of water spread and tank size measurements.

4.2 Biological aspects An assessment of the biological resources was critical since the output of the intended

development is directly related to this. These aspects are also limiting factors that need to

be taken into account in order to succeed.

4.2.1 Capture Fisheries

During the course of the last 50 years new species have been introduced into the Sri

Lankan reservoirs, species which are presently well established. Although some

restocking programs have been done in the study area, the majority of the fish population

is breeds and recruit naturally.

Production assessment reveals generally good fish production obtained mainly from

collective harvest obtaining an average of 50 kg/ha annually (Figure 9). Looking more

closely radial tanks; although being small and mostly highly seasonal, have better

production (kg/ha) than perennial tanks such as axial 3, even though the results were

observed in a drought year.

53

In terms of the fish caught the predominant species are tilapia species (around 50% of all

species) [Figure 10]. These species together with snakehead and small indigenous species

(SIS), are commonly found in most of the tanks are a part of the villagers diet.

It has to be pointed out that the involvement of man in the success of these species

survival and spread is minimal, which shows a big potential if fish culture is put in

practice.

4.2.2. Macrophytes

The presence of aquatic plants in the tanks is a factor that cannot be ignored since on

average 50% of the tank water surface is covered by macrophytes (Figure 15). The main

species present in most of the tanks are Nelumbo nucifera (Figure 15) and Nymphacea

lotus (Figure 16), which do not represent major disturbance for fishing and are source of

food for fish. The introduced noxious Salvinia (Figure 11), although it has heavy negative

impacts on the fishery and its culture, is only present in small amounts and in few tanks,

mostly perennial. Its presence appears to be mainly related to fishing activity, which is

greater in these tanks with the salvinia being spread mainly via fishing nets.

Other macrophytes are submerged plants, which although very abundant in most tanks,

their real abundance has not been properly assessed in this study, mainly due to the

difficulty in locating them in deeper parts of the tank during data collection; further study

of such plants is required. Their quick recovery and spread represent a problem mainly

for bathing activities in littoral areas.

In terms of abundance in the different tanks, the radial and the axial 1 tanks have the

lowest encroachment, below 40% (Figure16), and having as main species Nelumbo

nucifera, Nymphacea lotus and emergent grasses, making these tanks partially free of

macrophyte infestation problems.

Although a slight relationship between encroachment and fish production is appreciated

(Figure 17, 18), no conclusive results have been obtained. The low macrophyte presence

and high production in radial tanks could be an indication for such relationship, but

further analysis is required to test the hypothesis.

54

A more exhaustive study is recommended, using a more accurate system to estimate the

total tank area covered by macrophytes, plus a more detailed description of aquatic plants

present in such tanks.

An effective method to control macrophyte infestation is tank rehabilitation, which keeps

the tanks clear of macrophytes (<31% encroachment) for at least 3 years (Figure 19). Of

course, the rehabilitation process also affects the fish habitat, but such relationships have

not been looked at in this study due to insufficient data. Apart from desilting, carried out

in a few tanks, regular manual removal is practice only around bathing areas and some

fishing spots. Other control methods such as use of chemicals seems to be economically

non-viable specially for poor communities, unless provide by the government. The use of

bio-controls such as grass carp, water buffalo, beetles, etc, could be put into practice as in

other countries good results have been obtained (Gupta, 1987), but further research is

needed, to establish possible impacts.

4.3 Social-economic aspects

Poverty is an aspect, which seems to be related to the tank position within the cascade

system and to their seasonality. As population grows and space availability is reduced

people tend to be push towards the upper watersheds, which have less resources than the

bottom ones.

People at the bottom watershed tend to depend more in agriculture and the ownership of

land for other uses is bigger (Figure 21). This characteristic gives a more stable economic

situation. Those people at the radial and axial 1 tanks seem to rely more on natural

resources like hunting, illegal activities, fishing, poaching, etc. due to their lack of land

ownership.

Temporary labour, is more important in communities in the watershed among more

seasonal tanks (Figure 22). For instance at axial 1a 20% of the population relies on such

temporary labour, perhaps due to the high seasonality of these tanks which dry out

entirely every year requiring villagers to look for alternatives. On the other hand, because

radial tanks are not that highly seasonal more work is available within their own village.

At perennial tanks (A2, A3) the dependence on temporary labour is quite low, since they

have plenty of resources and land to exploit.

55

Another indicator of wealth is the housing (figure 23). In the study area the abundance of

temporary houses increases towards the more seasonal tanks and normally higher in the

cascade. At the axial 1a tanks the abundance of permanent houses (67%) could be due to

the great amount of f-farm labour which bring labour money from other villagers.

In Sri Lanka an ancient social division define a series of social groups or caste. Caste

which are closely related to wealth, although nowadays such traditional division is losing

in strength, still the differences can be appreciated. Typically higher caste peopleare

wealthier than those from lower castes.

Lower castes are present in higher numbers in radial tanks, where in axial 2 and 3 tanks

the majority of the caste are gobis (farmers). Although the relationship between caste and

wealth does not always apply, the distribution of lower castes towards radial and axial 1a

tanks is significant (Figure 24).

4.4 Conclusions

Seasonal tanks at the study area have a great potential for aquaculture. Although they do

not have the water availability that perennial tanks have, the knowledge about its water

availability cycle will allow to plan precisely the culture of fish in a sustainable manner.

The natural fisheries production of seasonal tanks is acceptable and not lower (kg/ha)

than in the less seasonal, supporting common fish species, which is part of the current

people’s diet.

Possible constraints like macrophytes infestation has been probed to be minimal

compared to the perennial tanks. Also social constraints are fewer than in the other tanks

due to their economic position, which makes them more open towards new strategies

such as fish culture.

Acceptable bio-physical conditions plus less possibilities of social constrains makes the

seasonal tanks a potential target for fish culture, but still the big issue in the study area are

the villagers priorities, where fisheries is at the bottom of the list and irrigation and

bathing are by far the main priorities. Priorities, which are believed by the villagers to be

affected if fishing, take place. Therefore the main impediment for the aquaculture

development success are the social aspects which still have strong traditional values.

56

References List

Abeywickrema, B.A, 1955. The origin and affinities of the flora of Ceylon Proc. Ceylon Asso. Advmt. Sci., Part 2: 1-23. Amarasinge U.S, 1985. Studies on the exploitation of minor cyprinids in Parakrama Samudra, a man made lake in Sri Lanka, using gill-nets. Journal of national Aquatic Resources Agency. Amarasinge U.S, 1990. Minor cyprinids resources in a man-made lake in Sri Lanka: a potential supplementary source of income for fishermen. Fisheries Research: 81-89. Amarasinge U.S, 1994. A synthesis on the management of the capture fisheries of Sri Lanka perennial reservoir Vidyodaya. Journal of Science, 5 (1). pp23-40. Chandrasena J.P.N.R. An illustrated manual of rice-field weeds in Sri Lanka. Publication #19. Department of Botany, University of Colombo, Sri Lanka. pp22-25 DAS 1996. Tabulated data presented by Wayamba Development Authority, Kurunegala, Sri Lanka. pp 30-31 De Silva S.S, 1983. Reproductive strategies of some major fish species in Parakama Samura reservoir and their possible impact on the ecosystem- a theoretical consideration. In: Limnology of Parakrama samura (F. Schiemer ed) pp183-191. W. Junk publishers. The Hague. Netherlands. De Silva, S.S and Sirisena H.K.G, 1987. New fish resources of reservoirs in Sri Lanka: feasibility of introduction of a subsidiary gill-net fishery for minor cyprinids. Fisheries Research. 6. 17-34. De Silva, S.S., 1988. Reservoirs of Sri Lanka and their Fisher ies. FAO Fish. Technical Paper (298):128p. De Silva, S.S, 1996. The Asian inland fishery with special reference to reservoir fisheries. A reappraisal. In: Perspective in Tropical Limnology (F. Schiemer and K.T. Boland (eds). Pp 321-332. Academic Publishing bv. Amsterdam, The Netherlands. De Silva, W. Indralal, 1997. Population Projections for Sri Lanka:1991-2041. Institute of policy studies. Colombo. Sri Lanka. pp 51-56 Edward, P. Food potential of Aquatic Macrophytes. 1980. Manila, Philippines, International center for Living Aquatic Resources Management. Fernando , C.H, & Indrasena, H.H.A, 1969. The freshwater fisheries of Ceylon. Bull. Fish. Res. Stn. Ceylon, 20:101-34.

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Garaway C.J, 1995. Communal ponds in NE Thailand under different use-right systems:A participatory rural appraisal of their differing roles in peoples’ livelihoods. London (Imperial College) Gunawardena D. C. 1968. The flowering plants of Ceylon. An etymological and historical account of the flowering plants of Ceylon. Lake house investment LTD publishers. 1st edition. Gupta O.P. 1987. Aquatic weed management. A textbook an manual. 2nd edition. Today and Tomorrow printers and publishers. New Delhi. India. Hasnip N, Vincent L, Hussein K, 1999. Poverty reduction and irrigated agriculture. Rome, Italy, Food and Agriculture Organization of the United Nations. International Program for technology and research in irrigation and drainage. Itakura, J and Abernethy L. Charles, 1992. Water Management in a tank cascade irrigation systems in Sri Lanka. International irrigation management institute. Working Paper # 24. Colombo. Sri Lanka. Junk W. 1973. Aqautic weed in S.E. Asia. Procedings of a regioanl Seminar on Noxious Aquatic Vegetation, New Delhi. The Hague publishers. Pages 12-17. Kaufman, P. B. 1989. Plants: Their Biology and Importance. New York, NY: Harper and Row, Publishers. Miles, M. B, Huberman A.M, 1994. Qualitative Data Analysis. London, Sage Publications. Murray F.J, 1999. The Nature of small scale Farmer Managed Irrigation Systems in North West Province, Sri Lanka and the potential for Aquaculture. Stirling University. Aquaculture in Small-Scale Farmer Managed Irrigation Systems. Murray F.J, 1999. Summary of cultivation strategies and water management of sheds of Anamaduwa and Giribawa research. Stirling University. Aquaculture in Small-Scale Farmer Managed Irrigation Systems. Murray F.J, Koddithuwakku S & Little D, 2000. Fisheries Marketing Systems in Sri Lanka and the relevance to Development of the local Reservoir capture and culture-based Fisheries. Reservoir Fisheries Biology & Management. Stirling University. Aquaculture in Small-Scale Farmer Managed Irrigation Systems. Murray F.J, & Little D, 2000. The Lowland Dry Zone of Sri Lanka: Site for Study of Aquaculture Development in the humid Tropics and methodology for Participatory Situation Appraisal. Stirling University. Aquaculture in Small-Scale Farmer Managed Irrigation Systems.

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NARA, 2000. Sri Lanka Fisheries Year Book (1999). Socio-economics and marketing Division, National Aquatic resources Research and development Agency, Colombo, Sri Lanka. Nathaniel, S, 2000. Integration of Aquaculture within irrigation systems; an overview of inland capture and culture fisheries in Sri Lanka with special reference to Mahaweli System H. Department for International Development. Working paper S-5. Newcastle. U.K. Niven C, Noble J, Forsyth S, Wheeler T, 1999. Sri Lanka. Lonely Planet publications. Seventh edition. Hawthorn, Australia. pp 10-16 Pemadasa, M.A, 1984. Grasslands in ecology and biogeography in Sri Lanka. Edited by C.H. Fernando. The Hague, The Netherlands, W. Junk Publishers, pp. 453-92. Perera, M.P, de Silva, M.B.G, 1997. Atlas of Sri Lanka. Arjuna Consulting Co Ltd. First edition. Sri Lanka. pp 23-27 Pet, J.S and Piet G.J, (1993). The consequences of habitat occupationand habitat overlap of the introduced Oreochromis mossambicus and indigenous fish species for fishery management in Sri Lanka reservoir. Journal of Fish Biology, 43 (Supplement A) 193-208. Penthiyagoda R, Rodrigo R. 1993. A revised handbook to the Flora of Ceylon. The wildlife Heritage Trust of Sri Lanka. Colombo. Sri Lanka. Pethiyagoda, R, 1999. Fishes in Trouble - the decline and fall of Sri Lanka’s freshwater fish fauna. Loris. 22 (2); 56-64. Piet G.T, 1996. Consequences of the eco-system perspective for the management of a tropical reservoir fishery. In: on the ecology of a tropical fish community (G.. Piet Ed.) pp 161-168. Thesis. Land bouwuniversiteit Wageningen. The Netherlands. Sakthivadivel, Nihal Fernando and Jeffrey D. Brewer, 1997. Rehabilitation planning for small Tanks in Cascades: A methodology based on rapid assessment. International Irrigation Management Institute. Research Report 13. Colombo, Sri Lanka. Smith, J.K, 2000. Conceptualising Conflict in Natural Resource Development Projects. University of Reading, Reading. Stern, K. R. 2000. Introductory Plant Biology. Toronto, Ont: McGraw-Hill.

59

Appendix 1. Average annual rainfall and temperature in Sri Lanka

(Source Perera et al 1997)

60

Appendix 2. Monsoon rainfall (Source Perera et al 1997)

61

Appendix 3. Sri Lanka Surface water (Perera et al 1997)

62

Appendix 4. Sri Lanka’s Population density distribution (Perera et al; 1997)

63

Appendix 5. Data Clearing Methodology

The following appendix describes the main methods used during the data clearing

process. This information refers to the cascade typologies data include in the attached

disc (Appendix )

1) Hydrology Spreadsheet

Maha yield (bush/ac, number/year)

Separation in two columns: a) bush/ac b) number/year

Units change: bush to Kg (1=22) and ac to ha (2,47 to 1)

Problems: Inconsistency in values ex. 75-85 bush/ac

Solution: use of a middle value. Ex. 80 bush/ac

Yala yield (same process applied as in Maha)

Type of crop has been delete since only 4 tanks had available information.

Tank access

CPR= Common property, T= Temple.

Catchment area

Regrouping and unit change: Group I: 0-10 ac (0-4,04 ha)

Group II: 10-50 ac (4,04-20,24 ha)

Group III: 50-100 ac (20,24-40,48 ha)

Group IV: 100-250 ac (40,48-101,21 ha)

Tank bed cultivation

RFP (top): change to “yes” group II

Paddy: change to “yes” group I

64

Command area

Units change: ac to ha (1:2,47)

Problems: Inaccurate data, ex. 20-25 ac.

Solution; use of middle value, ex. 22 ac

Maximum Depth, Maximum water spread, dead storage, Minimum residual waters,

Yala Spill Frequency, Maha spill frequency, to all the mentioned factors the same

Procedure as in the command area has been applied.

Maha Spill months

Grouping: Group I: November, Group II: December, Group III: Nov-Dec,

Group IV: Dec- January, Group V: Jan-Dec, Group VI Oct-Nov.

Yala Spill months:

Grouping: Group I: April, Group II: May, Group III: June, Group IV: Apr-May

Group V: May-June

Dry Frequency:

0.5 means 1 year out of 10 years, and 0.25 1 year out of 20.

Dry Months

Grouping: Group I: August, G II: July-Aug, GIII: Jul-Sept, G IV: Aug-Sept,

G V: June-July, G VI: Feb-March, G VII: Apr-May, G VIII: Jun-Sept

G X : July-Oct, G XI: March-May, GXII: Aug-Oct, G XIII March-Oct

G XIV: May-Sept, G V: June-Oct, G VI: March-Oct

Season Class

P(St) and P(HS), typing errors convert to P and HS

65

Cropping intensity

Some cells values given were unclear, ex: 0-25%, after consulting with the data entry

responsible, data was tidy to 25%.

Number of rains

Raw data ex: 2-3 R, was changed to Group I: 1-2 rains, Group II: 2-3 rains,

Group III: 3 rains.

Data with just FR and HF was place in Group I and II respectively.

Time for field preparation

Grouping: 1 week: Group I, 2 weeks: G II, 3 weeks: G III, 4 weeks: G IV,

1-2 weeks G V, 2-3 weeks G VI, 3-4 weeks: G VII.

Preparation: rain or stored water (number /year)

Separated in two columns a) number b) year

Rice variety (number/year)

Value 3.5 were round to 3 months since is the same type.

As before separation into two columns (number and year)

Variety, duration and synchronisation

Variety: Synchronise or not synchronise

Duration: Synchronise or not synchronise.

Grouping: Nadu: Group I, Samba: Group II, Nadu/Samba: Group III.

Release Numbers

If two values give, the mean value has been inserted.

In case of ex: 6-7 the higher number was taken (this method has been applied to all the

different cases in all the spreadsheet)

66

Unclear data, where values given refers to one season or the whole year, season, request

further research to clarified. Provisionally taken as year wise.

Release Synchronisation (days)

Separation into two columns, a) days and b) Synchronisation (yes or no)

2) Fisheries Spreadsheet

Priorities uses of water

New ranking given (1-5), Most important (1), less important (5)

Use or systems or tank for bathing.

New ranking 1-10, 10 more used, 0 no use at all.

Same ranking applied for other systems, tanks and livestock.

External Participants

Split in different columns, each column is a different tank. Those tanks where external

participation took place have been mark with a 1. The total number of participants has

been omitted.

Other external participants not included.

Pre Collective Fishing patterns

Split in 6 columns, gear type (4 different gears) and ownership type (2 types)

Period of time is been omitted.

Species quantity stocked

The Number is not very accurate.

Tanks fished by villagers

(Number of households participating at the village, score volume of fish.

67

Data split is three different columns: a) Number of tanks fished by villagers

b) Number of households involved

c) Rank in terms of amount of fishing time

Problems: Given 2 values ex: 3-4 households, the higher was chosen.

Socio-economic characteristics of self-consume fishermen

Split in 5 columns: landless, youth, farmers, coolie (temporal labour) and OFL.

Those tanks where the different characteristics took place were mark with a “1”.

Collective Fishing Harvest (Kg) by species.

Divided in different columns by species (two sections: percentage and Kg)

Inconsistency data, most of the Kg data missing has been worked out based on the

percentage.

Uses of Harvest

Division on 4 columns.

Coding 1:yes, 2:no.

In all the cases, where fishes species are used, is no clear whether the data collector made

a difference between Ori. Mossambicus and Ori. Nilotica.

Livestock spreadsheet

Local Sharecroppers under tank

Number of households, surnames and Acres (pass into hectares)

Due to the unavailability of surnames data with area information only number of

households has been used.

68

Appendix 6 : Macrophytes Taxonomic identification 1) Salvinia molesta (Salvinia or velvet weed)

Division: Polypodiophyta

Class: Polypodiopsida

SubClass: Salviniidae

Order: Salviniales

Family: Salviniaceae

A free floating sporophyte. Leaves in ternate whorls on horizontal rhizones; a pair of

leaves floating third one submersed, finally dissected to sporocarps. In Thinly populated

mats the floating leaves are flat oval to egg-shaped and about 1 cm wide. But in dense

mats the salvinia leaves are conduplicated folded up to 4 cm wide. Salvinia molesta

leaves are hairy tom provide buoyancy. Propagation largely by offsets; it’s asexual

reproduction is uncertain (Junk, 1973).

Mostly on stagnant or slow moving fresh-water, shallow or deep; ponds, lakes,

irrigation canals, watercourses, in swampy marshes or inundated rice-fields in wetter

regions. Often very abundant covering whole water surfaces (Penthiyagoda, 1993)

Figure 1 &2 (photo and drawing)

Figure 25. Salvinia molesta physiology by R,G, Howell. Figure 26. Salvinia molesta in the wild.

The popular belief is that this water fern was first introduce into Sri Lanka by a

botanist who had brought it for scientific study, and it is presumed that during a spell

69

of very heavy rain this plant had escaped with the overflowing water into the city

drainage net work. Due its rapid growth and multiplication it soon establishes in the

low-lying areas and waterways in the suburbs of Colombo. The re was general belief

that the British army had introduced this weed to camouflage the waterways around

Colombo ( Junk, 1973).

2) Pistia stratiotes (water lettuce)

Division: Magnoliophyta

Class: Liliopsida

SubClass: Arecidae

Order: Arales

Family: Araceae

Perennial, free floating herb, sometimes anchored to wet mud. Leaves tongue-shaped, in

shell like rosettes, up to 20mm wide puplpy with aerenchyma to hold the plant above the

water level light green in colour and covered with tiny hydrophobic trichomes.

Inflorecent a spandix with spathe in the hollows of the leave. Propagation by offsets buds

and seeds.

Introduced as an ornamental plant. It is a floating plant which normally grows in stagnant

water or slowly flowing water. Pistia is also able to grow in wet or marshy areas where

there is little water. Triman reports that is able to grow in somewhat brackish water near

the coast (Junk, 1973)

.

Figure 27. Pistia stratiotes by Murray A.

70

3) Echhornia crassipes (Water hyacinth)

Division: Magnoliophyta

Class: Liliopsida

SubClass: Liliidae

Order: Liliales

Family: Pontederiaceae

Floating or in shallow water rooting perennial plant with axiallary stolons, forming easily

detachable new plants at the ends. Stems densely covewred with petiole bases and roots

and numerous rootless. Leaves in rosette, thick, glossy green, broadly ovate, with

subcordate or rounded base and obtuse apex, 7-25 cm in diameter, glabrous; petiole

spongy, up to 30 cm in adult leave, gradually narrowed upwards. Flowers zygomorphic,

bisexual, in long –stalked, erect spikes, up to 50 cm long, bearing 18-35 flowers, bending

downwards after flowering; penducles with 2 bracts (spathes), tubular; perianth also

tubular; tube 15-18mm long base green, top pale green; lobes 6, mauve in colour, the

anterior one 3-4 cm long. Stamens 6, attached to perianth tube, the 3 anterior small, other

3 much longer. Ovary superior, 3-celled, multi-ovulate, axile placentation; style long,

slender; stigma hairy with 3 lobes; capsule membranous, 3-valved, surrounded by

persistent perianth. Seeds many, minute, ribbed, obovoid. It propagates by seeds and

plant fragments (figure xxx).

Introduce by man, mainly due to the belief among the people that the flowers of this

weed produce a mauve coloured dye, which could be used to counterfeit currency notes.

Another misconception about this plant is related to its suppose ‘ayurvedic medicine’.

Many times people have made efforts to grow it in private pools and ponds. The plant

actually used in medicine in not the water hyacinth but Monochoria hastada (Diya-

habarala).

71

Figure 28. Eichhornia crassipes Figure 29. Eichhornia crassipes by IFA .

4) Nelumbo nucifera (Nelum or sacred lotus)

Division: Magnoliophyta

Class: Magnoliopsida

Family: Nelumbonaceae

Perennial water plant. Leaves peltate or orbicular, 60-90 cm wide without any slit.

Flowers elegant white-pin, sweetly scented, prominently emerged on long stalks. Fruits

spongy, flat-topped 10-15 cm in diameter. Propagation by seeds and farinaceous, long

fleshy edible rhizomes.

Figure 30. Nelumbo nucifera by Fagg, M Figure 31. Nelumbo nucifera at the tank

72

5) Ceratophyllum demersum ( Veru,Coontail / Hornwort) Division Magnoliophyta Class Magnoliopsida, the Dicotyledons Subclass Magnoliidae Order Nymphaeales Family Ceratophyllaceae. Genus Ceratophyllum. Description: Free floating or attached to sediment, stems

branched and often up to 1 m long. Coarse, weakly and irregularly toothed compound

leaves (2/5"- 1 3/5" long) retain their shape when removed from the water.

Flowers: Small purple clusters (rarely)

Because its feathery leaves are arranged in whorls on the stem, this plant resembles a

racoon's tail. The fan-shaped leaves are best observed in the water. They look feathery

because each leaf is divided into many narrow segments. Each leaf has several small

teeth on the midribs. These tiny teeth give the plant a rough feel when pulled through the

hand. Coontail's flowers are very small and rarely seen.

Figure 32. Ceratophyllum demersum Figure 33. Ceratophyllum demersum leaves

73

6) Eleocharis dulcis (Water chestnut) Phyllum: Angiospermae Class: Moncotyledonae Order: Cyperalis Family: Cyperaceae This plant has stolons and tubers. Its culms are robust, transversely septate of 50-100

cm tall. Leave blade reduced with purplish sheath, 10-20 cm long. Inflorescence with

single spike, terminal, cylindrical 1.5-3.0 cm long. Spikelets sessile round 2-5 cm long.

Perennial sedge and propagated by stolon, tubers and seeds. An apical bud emerged

from the tubers and then swallon to form a basal bulb(corm) usually at the soil surface.

Arial shoot and root will grow from the germinated tuber. Branches of rhizomes will

eventually form an extensive network underground. These rhizomes usually domiant in

undisturbed areas but the dormancy break when they are disturb or break in fragment

during ploughing. This indicate that ploughing initiate the growth of this weed.

This sedge are found in aquatic conditions such as rice fields, swamp and waste lands.

Figure 34. Eleocharis dulcis 7) Nymphoides indica Division: Magnoliophyta Class: Magnoliopsida Subclass: Asteridae Order: Solanales Family: Menyanthaceae

74

Genus : Nymphoides Flower Shape: Stellate Flower Color: White Flower Size: 1" Leaf Shape: Ovate to circular Leaf Coloration: Green Leaf Size: To 12" Leaf Spread: To several feet This is by far the largest of the Nymphoides. Its leaves can grow to 12"

in diameter a and its flowers are larger, have more petals, and are fringed,

instead of being plainly edged. Its flowers are produced from

beneath the leaf, as with N. cristata. These flowers have 7-9 petals,

though, instead of the standard 5. As the season winds down, the plants

reduce to tuber clusters and most of the original stems die off, allowing

the offspring to drift away to their fates.

Figure 35. Nymphoides indica photo Figure 36. Nymphoides indica drawing

75

8) Utricularia vulgaris (Bladderwort) Family: Lentibulariaceae Distribution: Fresh waters, usually found in ponds and reserviors, but ca also exist in

slow moving tidal areas.

Description: Very fine, much branched plant with numerous bristle -like alternate leaves 1

to 2 cm long and 0.5 mm wide. re rootless. They have main stems from which lacy, often

complex leaves grow. Bladderwort flowers are usually bright yellow the flowers have

two "lip-like" petals of about equal size. Flowers are on long stalks that emerge several

inches above the water. The carnivorous bladders are attached at regular intervals along

the linear leaf segments.

Reproduction: By seed

Figure 37. Utricularia vulgaris at the tank

Figure 38. Utricularia vulgaris physiology

76

Appendix 8. Statistical analysis results

Table 7. Chi square test results from water input and seasonality data. Significance values below 0.05 are significant.

Table 8. Chi-square test results from maximum water spread and water availability. Significance values below 0.05 are significant.

Table 9. Analysis of variance (Univariate) test results from the annual fisheries production. Significance values below 0.05 are significant.

Chi-Square Tests

81.964a 12 .00083.517 12 .000

16.132 1 .000

91

Pearson Chi-SquareLikelihood RatioLinear-by-LinearAssociationN of Valid Cases

Value dfAsymp. Sig.

(2-sided)

15 cells (75.0%) have expected count less than 5. Theminimum expected count is .40.

a.

Chi-Square Tests

84.969a 9 .00095.176 9 .000

30.219 1 .000

91

Pearson Chi-SquareLikelihood RatioLinear-by-LinearAssociationN of Valid Cases

Value dfAsymp. Sig.

(2-sided)

9 cells (56.3%) have expected count less than 5. Theminimum expected count is 1.33.

a.

Tests of Between-Subjects Effects

Dependent Variable: PRODUCTI

279338.710a 8 34917.339 4.506 .00066608.722 1 66608.722 8.595 .00569306.321 1 69306.321 8.943 .004

112246.188 4 28061.547 3.621 .01161919.543 3 20639.848 2.663 .058

395219.396 51 7749.400836512.232 60674558.106 59

SourceCorrected ModelInterceptTANK_TYPFISHITYPTANK_TYP * FISHITYPErrorTotalCorrected Total

Type III Sumof Squares df Mean Square F Sig.

R Squared = .414 (Adjusted R Squared = .322)a.

77

Table 10. Analysis of variance (Univariate) test results from fish species distribution. Significant values below 0.05 are significant.

Table 11. Analysis of Variance (Univariate) test results from tank macrophytes distribution Significant values below 0.05 are significant.

Table 12. Analysis of Variance (Univariate) test results from macrophytes distribution at the different tanks. Significance values below 0.05 are significant.

Tests of Between-Subjects Effects

Dependent Variable: CATCHTRA

8.590a 15 .573 6.506 .00015.388 1 15.388 174.819 .000

3.898E-02 3 1.299E-02 .148 .9317.389 3 2.463 27.984 .000

.561 9 6.237E-02 .709 .7007.746 88 8.802E-02

34.809 10416.336 103

SourceCorrected ModelInterceptTANKTIPOFISHSPECTANKTIPO * FISHSPECErrorTotalCorrected Total

Type III Sumof Squares df Mean Square F Sig.

R Squared = .526 (Adjusted R Squared = .445)a.

Tests of Between-Subjects Effects

Dependent Variable: ENCROACH

13.427a 4 3.357 67.587 .00012.121 1 12.121 244.068 .00013.427 4 3.357 67.587 .00022.001 443 4.966E-0247.505 44835.428 447

SourceCorrected ModelInterceptSPECIESErrorTotalCorrected Total

Type III Sumof Squares df Mean Square F Sig.

R Squared = .379 (Adjusted R Squared = .373)a.

Tests of Between-Subjects Effects

Dependent Variable: SURFCOV

16.206a 24 .675 14.243 .00010.571 1 10.571 222.993 .00010.472 4 2.618 55.222 .000

.907 4 .227 4.782 .0011.489 16 9.304E-02 1.962 .015

16.498 348 4.741E-0245.405 37332.704 372

SourceCorrected ModelInterceptESPECIESTANKTYPESPECIES * TANKTYPErrorTotalCorrected Total

Type III Sumof Squares df Mean Square F Sig.

R Squared = .496 (Adjusted R Squared = .461)a.

78

Table 13. Chi-squares test results from desiltation impacts. Significance values below 0.05 are significant

Table 14. Analysis of Variance (Univariate) test results from distance to infrastructures from the different tanks.

Table 15. Analysis of variance (Multivariate) test results from ownership distribution. Significance values below 0.05 are significant.

Chi-Square Tests

13.847a 4 .00815.398 4 .004

7.940 1 .005

76

Pearson Chi-SquareLikelihood RatioLinear-by-LinearAssociationN of Valid Cases

Value dfAsymp. Sig.

(2-sided)

4 cells (44.4%) have expected count less than 5. Theminimum expected count is 1.79.

a.

Tests of Between-Subjects Effects

Dependent Variable: DISTANCE

432.683a 19 22.773 5.529 .000875.694 1 875.694 212.609 .000253.070 3 84.357 20.481 .000

9.019 4 2.255 .547 .70139.490 12 3.291 .799 .650

362.454 88 4.1191913.250 108

795.137 107

SourceCorrected ModelInterceptINFRAESTTANKTPINFRAEST * TANKTPErrorTotalCorrected Total

Type III Sumof Squares df Mean Square F Sig.

R Squared = .544 (Adjusted R Squared = .446)a.

Multivariate Testsc

.842 29.302a 2.000 11.000 .000

.158 29.302a 2.000 11.000 .0005.328 29.302a 2.000 11.000 .0005.328 29.302a 2.000 11.000 .000.928 3.463 6.000 24.000 .013

.262 3.503a 6.000 22.000 .0142.098 3.497 6.000 20.000 .0161.663 6.651b 3.000 12.000 .007

Pillai's TraceWilks' LambdaHotelling's TraceRoy's Largest Root

Pillai's TraceWilks' LambdaHotelling's TraceRoy's Largest Root

EffectIntercept

TANKTYPE

Value F Hypothesis df Error df Sig.

Exact statistica.

The statistic is an upper bound on F that yields a lower bound on the significance level.b.

Design: Intercept+TANKTYPEc.

79

Table 16. Analysis of Variance (Univariate) test results form coolie labour at the tanks. Significant values below 0.05 are significant

Table 17. Analysis of variance (Univariate) tests results from housing characteristics Significant values below 0.05 are significant.

Table 18. Analysis of variance (Univariate) test results from caste and watershed relationship. Significance values below 0.05 are significant.

Tests of Between-Subjects Effects

Dependent Variable: COOLIE

298.725a 4 74.681 3.439 .033460.313 1 460.313 21.196 .000298.725 4 74.681 3.439 .033347.473 16 21.717

1000.440 21646.198 20

SourceCorrected ModelInterceptTNKTYPErrorTotalCorrected Total

Type III Sumof Squares df Mean Square F Sig.

R Squared = .462 (Adjusted R Squared = .328)a.

Tests of Between-Subjects Effects

Dependent Variable: NUMBERS

27406.935a 14 1957.638 2.411 .00922969.419 1 22969.419 28.288 .000

9648.808 4 2412.202 2.971 .0265841.888 2 2920.944 3.597 .0336027.954 8 753.494 .928 .500

53591.016 66 811.985123755.000 81

80997.951 80

SourceCorrected ModelInterceptTANKTIPHOUSETYPTANKTIP * HOUSETYPErrorTotalCorrected Total

Type III Sumof Squares df Mean Square F Sig.

R Squared = .338 (Adjusted R Squared = .198)a.

Tests of Between-Subjects Effects

Dependent Variable: TANK#

18215.050a 23 791.959 42.165 .00026373.066 1 26373.066 1404.135 .000

527.134 4 131.784 7.016 .00012122.417 6 2020.403 107.569 .000

3039.562 13 233.812 12.448 .000

694.950 37 18.78277531.000 61

18910.000 60

SourceCorrected ModelIntercept

TANKTYPCASTE

TANKTYP * CASTEErrorTotal

Corrected Total

Type III Sumof Squares df Mean Square F Sig.

R Squared = .963 (Adjusted R Squared = .940)a.

80