Topic 1PRINCIPLES OF FISH PRODUCTION IN PONDSPond ecosystem and productivity

In a pond of any kind there exists a dynamic system of material/energy cycle, broadly between all the living organisms and the non-living environments which are, in nature, inseparably interrelated and interact upon each other.

The non-living substances of pond ecosystem include the inorganic and organic compounds. These compounds remain in solution in pond water, in reserve in bottom deposits as well in the living organisms - both plants and animals.

The living organisms (biotic community) in a pond ecosystem, consisting of all sorts of plants and animals, are broadly categorized into two main groups:

The autotrophic community viz. the producers include all the green plants which produce complex organic substances or cell materials from inorganic soluble nutrients in presence of sun light (photosynthesis). The producers are of two types -- phytoplankton and macrophytes.

The minute floating algae or phytoplankton distributed in the pond water column mainly throughout the light-limited limnetic zone. Abundance of phytoplankton population in water gives greenish colour. Production of phytoplankton is thus dependent on sun light and available soluble nutrients in water. Tropical fish ponds are generally found rich in natural food organisms as the sun light duration is longer.

The macrovegetation, though fall under producer group, in reality, their contribution is negligible in primary productivity of well managed fish pond. They are, however, found inhibitor in fish production system if not utilized properly as fish feed.

The heterotrophic community in a fish pond ecosystem comprising of two major groups of organisms namely:

The consumers - the organisms depending on other organisms living or dead for food such as zooplankton, insect larvae, fish etc. The consumers group (benthic invertebrates and bottom feeding fish) subsisting on organic detritus are called detritivores.

The decomposers - the group of heterotrophic organisms such as bacteria and fungi break down the dead plants and animals and release partially decomposed materials and inorganic nutrients into pond water for utilization by the producers viz. phytoplankton and macrophytes. The decomposers are most abundant at the pond bottom where the dead plants and animal bodies are most abundant.

The food chains or energy pathways in a pond ecosystem are of two types: the autotrophic food chain and the heterotrophic food chain.

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Autotrophic food chain - It is the solar energy dependent food chain which begins with the plants, basically phytoplankton, at the pond surface and then sequentially pass through primary consumers (zooplankton and planktivours fishes) to secondary and tertiary consumers (carnivorous insects and fishes).

The pathways in autotrophic food chain are:

Phytoplankton fish⇒Phytoplankton zooplankton fish⇒ ⇒Phytoplankton zooplankton aquatic insects fish⇒ ⇒ ⇒

predator fish⇒

Heterotrophic food chain - This energy pathway starts from the decomposition of dead organic matters by the decomposing bacteria and fungi at the pond bottom and then pass through zooplankton - aquatic insects to fishes (secondary and tertiary consumers) as shown below :

Bacteria fish⇒Bacteria protozoa fish⇒ ⇒Bacteria Protozoa zooplankton Aquatic insect larvae fish⇒ ⇒ ⇒ ⇒

The productivity of a fish pond depends on the availability of dissolved nutrients in pond water which can be utilized for production of organic materials by the producers (mainly phytoplankton) using solar energy.

The sources of pond nutrients may be of organic and/or inorganic origin. Organic manure mainly supports the heterotrophic food chain while the inorganic fertilizers supports the autotrophic food chain. Both the pathways are closely inter-linked to each other. However, in most fish ponds, production largely depends on the solar energy dependent autotrophic food chain, but the ponds receiving high quantity of organic manures on regular basis have significant heterotrophic use of wastes by bacteria and protozoa.

Fish production not only depends on the rich food chains but also largely on the stocking density of fish as well as the species combination having different feeding and spatial niches - so that total fish food organisms of a pond originated from both the food chains are properly utilized by the fish.

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Topic 2FISH PRODUCTION WITH POLYCULTURE

2.1 CONCEPT OF POLYCULTURE

The concept of polyculture of fish is based on the concept of total utilization of different trophic and spatial niches of a pond in order to obtain maximum fish production per unit area. Different compatible species of fish of different trophic and spatial niches are raised together in the same pond to utilize all sorts of natural food available in the pond.

In general, undrainable pond is characterized by its diversified spatio-trophic environment comprising of various natural fish food organisms (Phytoplankton, Zooplankton, Periphyton, Macrophytes, Benthos and detritus) at different strata of pond water column as well as in the bottom. Selection of species in polyculture is thus very important. There should be a compatible combination of species with diversified feeding habit that should include planktivorous surface/column feeders to benthic/detritivorous bottom feeders as well as omnivorous to macrovegetation feeding fish species.

The possibilities of increasing fish production per unit area, through polyculture, is considerable, when compared with monoculture system of fish. Different species combination in polyculture system effectively contribute also to improve the pond environment. Algal blooming is common in most tropical manure fed ponds. By stocking phytoplanktophagus Silver carp in appropriate density certain algal blooming can be controlled. Grass carp on the other hand keeps the macrophyte abundance under control due to its macrovegetation feeding habit and it adds increased amount of partially digested excreta which becomes the feed for the bottom dweller coprofagous common carp. The bottom dwelling mrigal, common/mirror carp help re-suspension of bottom nutrients to water while stirring the bottom mud in search of food. Such an exercise of bottom dwellers also aerates the bottom sediment. All these facts suggest that polyculture is the most suitable proposition for fish culture in undrainable tropical ponds.

2.2 INTENSITY OF CULTURE PRACTICES

Considering the level of management in fish production, the following culture practices can be identified.

2.2.1 Extensive culture

Under this culture practice, no nutritional inputs (manure and feed) are applied to the pond. Fish solely depends on the natural feed available in a pond and hence the carrying capacity of a pond remain low, resulting in lower fish production.

Salient features are :

no nutritional inputs given to the fish fish rely on natural food produced in the pond low stocking density low fish production low production cost

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2.2.2 Semi-intensive culture

Semi-intensive culture is primarily a manure based culture practice where supplementary feeding is avoided or of very limited use. Carrying capacity of pond is higher than that of extensive culture and ensures higher production of fish.

Salient features are :

manure based culture practice rely mainly on natural fish food produced in the pond limited use of supplementary feed moderate stocking density fish production higher than in extensive system moderate production cost

2.2.3 Intensive culture

Under intensive culture practice total nutritional requirements of fish are satisfied with the application of high quality formulated, pellet feed. In addition, replenishment, aeration and/or recirculation of pond water is carried out in order to maintain oxygen rich, good quality water capable of high production per unit area of culture.

Salient features are :

use of formulated feed meeting total nutritional requirements replenishment, aeration or recirculation of pond water high stocking density highest fish production per unit area high production cost

Polyculture of three indigenous carps - catla, rui and mrigal is traditional in Bangladesh. However, the culture system depends primarily on natural productivity of the pond. Manuring and feeding are either irregular or not practiced at all. All these suggest that the practice of fish culture in Bangladesh is more or less extensive type or at best at semi-intensive level. As a result, the average yield is very low, around 1000 kg/ha/year. The farmers are keeping fish in ponds rather than doing fish culture in ponds. Though the inputs (manure, feed etc.) required for semi-intensive culture are locally available, the rural farmers are not trained to take advantage of the opportunities. On the other hand large scale introduction of intensive management of fish production at this moment does not seem to be a practical proposition. The intermediate technology of semi-intensive method of fish production using cheap and locally available manure and feed seems to be the appropriate technology for Bangladesh.

2.3 POND MANAGEMENT

Management of fish culture in ponds include successive stages starting from pond preparation to final harvesting of fish. The total package of pond management practices can be divided into three phases viz. pre-stocking management, stocking management and post-stocking management.

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2.3.1 Pre-stocking management

This is actually the pond preparation phase which includes renovation of pond, eradication of undesirable fishes and aquatic weeds, liming of pond bottom and base manuring of pond.

Characteristics of ideal fish pond and renovation of existing ponds

A pond of any size can be considered fit for fish culture. Although, a grow-out pond of 2–5 bigha that retains at least 2 m water round the year is found to be suitable for production of carps. The overall environmental conditions suitable for fish production are better in larger ponds than that of smaller ponds.

The bottom soil of an ideal pond should be loamy to clay-loamy. Such soil is best for fish pond because of its good water retention capacity, rich fertility that supports production of natural food organisms and lower turbidity.

The pond dyke should be free from large trees to facilitate maximum light fall and wind action. Sun light and wind action are very important factors for maintaining biological productivity of fish ponds. Ideally, the pond should have well built high dykes all around to protect the pond from flooding, to prevent entry of predators and weed fishes, and to prevent stocked fish from escaping.

Improvement of pond environment

Environment of a pond has direct impact on fish production. A pond with suitable environmental features would give higher fish production per unit area than that of a pond having adverse environmental conditions.

All the aquatic vegetations (floating, submerged or emergent) should be removed from the pond. They hamper primary productivity by absorbing available nutrients from water and soil and hinder normal penetration of sun light and wind action. The large trees on the dykes and their overhanging branches also adversely affect the pond environment by casting shadow and falling leaves, fruits etc. into water. All such trees and their branches should be trimmed.

The pond bottom should be made even to allow effective netting and harvesting of fish. The broken pond dyke must be repaired and well raised so that in and outward migration of fish can be avoided under normal flooding situation. Grass or other vegetables can be planted on the dykes which would help prevent erosion of dyke in monsoon months and alleviate turbidity problem as well. The Rodents are also one of the causes of dyke erosion as they make holes in the dyke. They are to be killed by traps and the holes are to be properly blocked.

Eradication of undesirable fishes

All the predatory and unwanted fishes must be eradicated from the pond prior to stocking the pond with the fingerlings of desirable species. This can be done either by complete dewatering the pond or by poisoning. Some commonly used efficient fish toxicants are mentioned here:

Rotenone

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Rotenone kills all the fish species except shrimps when applied @ 2–3 ppm. The killed fish is also suitable for human consumption. However, higher cost and unavailability are the negative points. Toxicity lasts for about 10 – 12 days.

Phostoxin

This is a kind of fumigant poison found in tablet form specially prepared for control of storage pests. Active ingredient is Aluminum phosphide (57%). Phostoxin has been found very effective in killing all sorts of fish @0.2 ppm. Toxicity lasts for around 10–15 days. The killed fish is also suitable for consumption.

Tea seed cake

In tea seed cake the active ingredient responsible for killing the fish is the Saponin. Tea seed cake is effective at 75–100 ppm. (5 – 10 ppm Saponin content). Before application, the tea seed cake should be soaked overnight and then broadcast over the pond surface. The toxicity lasts for about 10–12 days and the killed fish is fit for human consumption. In Sylhet and Chittagong area tea seed cake is readily available.

Mahua oil cake

Mahua (Basia latifolia) oil cake contains 4–6% Saponin and kill fishes when applied @ 250 ppm. The toxicity lasts for about 10–15 days under normal conditions. Killed fish is fit for human consumption. It also serves as a base manure in the pond.

Bleaching Powder

Bleaching powder, as fish toxicant has been found to kill fishes within 3–4 hours when applied @ 30 ppm. Its toxicity lasts for about 7–8 days in the pond. Killed fish is not fit for human consumption. It kills all sorts of biota in the pond. Repeated use may cause the reduction of pond productivity. This chemical has an excellent disinfecting effect besides oxidizing the decomposing matter on the pond bottom.

For calculation of actual quantity of poison required for a pond from the above mentioned concentration the following formula can be used :

Liming

Liming of a fish pond is highly recommended because of its following advantages:

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Lime neutralizes soil acidity and creates a buffer system to prevent marked diurnal fluctuations of the water from acidic to alkaline conditions.

Destroys fish pathogens and their intermediate life stages;

Converts unsuitable acidic condition of water to suitable alkaline condition;

Neutralizes iron compounds which are undesirable in fish ponds;

Promotes mineralization of soil which is desirable in fish ponds;

Settle excess dissolved organic matters and thereby reduces incidences of oxygen depletion;

Acts as disinfectant and improves hygienic condition of pond.

Apart from other advantages, the buffering action of calcium is the most important. Lime serves both the prophylactic and therapeutic purposes. Lime treatment for ponds should be done before initial manuring as given in Table-2.1.

Table 2.1 Quantity of lime to be applied in accordance with soil type

Soil pH Soil typeQuantity of lime (CaCO3)(kg/bigha)

4.0–4.9 Highly acidic 270

5.0–6.4 Moderately acidic 140

6.5–7.4 Near neutral 70

7.5–8.4 Mildly alkaline 30

8.5–9.5 Highly alkaline No liming

Source : Kumar (Manuscript)

For treating the pond bottom after dewatering, the quick lime [CaO] is the best. Application of quick lime @30–40 kg per bigha also disinfects the pond to some extent. For water treatment only the slacked lime [Ca(OH)2] should be used instead of calcium oxide.

Manuring

In undrainable ponds where the frequent change of water is a remote possibility the physio-chemical properties of pond water governing the biological production cycle are more or less a reflection of the bottom soil. In semi-intensive fish culture, considerable quantities of nutrient elements are removed from the pond ecosystem through fish production. Therefore, the fertilizer requirement vary depending on soil productivity levels (Table 2.2).

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Table 2.2 Amount of fertilizers required for ponds at high, medium and low levels of productivity

Pond productivity levels / rate of application (kg/bigha/yr) High Medium Low

Organic carbon (C) Cattle dung 700–1000 1100–1400 1400–3400

Nitrogen(N)*Nitrogen requirement 13–20 20–27 27–33

Urea (43–45%) 15–20 21–30 30–35

Phosphate (P2O5

*Phosphate requirement 7–10 10–13 13–17

Triple super phosphate (40–45%) 7–10 10–15 15–20

* It is expected that about half of the requirements of nitrogen and phosphate will come from organic manure application and hence the remaining half is to be compensated by application of inorganic fertilizers like urea and TSP.

Source : Kumar (Manuscript).

Organic manuring, besides being important as a means of adding the nutrients in water is also equally important for improving the soil texture. If there is shortage of organic manures, the application of inorganic fertilizers is recommended. A generalized schedule can be adopted in the absence of detailed soil and water analysis data (Table 2.3).

Table 2.3 Generalized fertilization schedule

Item Quantity (kg/bigha)

Base manuring (Pre-stocking)  

1. Chicken manure (dry) 250

(or)  

Cow dung 400

2. Urea   10

3. Triple Super Phosphate (TSP)    5

Regular (Post stocking)  

  Daily

1. Chicken manure  

a. dry without rice husk   5–10

b. dry with rice husk 12–17

c. fresh pure 10–12

  (or) Cow dung fresh 15–20

2. Urea        0.1       kg

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3. TSP        0.05      kg

The proper mode and timing of application of fertilizers are very important in order to get good results as well as avoid water quality problems. Manures/ fertilizers should be applied only when the other environmental conditions of water are suitable such as sunshine, good oxygen content and adequate water level etc. The best way of applying is to dissolve the fertilizers in water and spray throughout the pond surface. The best time for manuring is morning within 9–10 o'clock. Application of manure/fertilizer in late afternoon or evening may cause oxygen depletion in the early hours of the following day because of faster decomposition at night. During fully cloudy and rainy days, manuring has to be suspended. In case of algal blooming the manuring/fertilization has also to be lessened or stopped.

Manure and fertilizers are best utilized when the desired total dose is given in small portions. Daily manuring with small quantity has been found best for keeping optimum level of fish food organisms in pond throughout the fish production period. For example, the best utilized manure is from the animals reared together with fish under the integrated livestock-cum-fish culture system.

Water regulation

The average water depth in a pond is an important factor in fish culture. This, generally, depends on various factors like rainfall, evaporation losses, seepage, use of water for irrigation, etc. If necessary, water may be let in from nearby available sources during summer or drained out during monsoon to maintain desirable water depth in the pond. Heavy accumulation of metabolites at the bottom of ponds may deplete oxygen in the pond water during low water depths, adversely affecting fish growth. However, such problems generally not occur in seasonal ponds.

2.3.2 Stocking management

Procurement, transportation and stocking of quality fingerlings of different compatible species of fish in ponds are the activities to be undertaken under stocking management phase.

Species selection

Judicious selection of compatible fast growing species is of vital importance in maximizing fish production. A combination of six species, viz. Catla (Catla catla), Silver carp (Hypophthalmichthys molitrix), Rui (Labeo rohita), Grass carp (Ctenopharyngodon idella), Mrigal (Cirrhinus mrigala), and Common carp (Cyprinus carpio) fulfills the species selection requirement and has proven to be ideal combination for freshwater carp culture in Bangladesh. Of these, Catla and Silver carp are surface feeders, Rui is a column feeder, Grass carp is a macrovegetation feeder and Mrigal and Common carp are bottom feeders. The six species combinations have been found to yield maximum production and are generally preferable in the region. These species are the “back bone” of polyculture. Some supplementary species may also be introduced. Thai sarputi (Puntius gonionotus) is very popular and can be used in a polyculture system. A list of compatible species with their spatio-trophic habits is given in Table-2.4.

Table 2.4. Compatible carp species for polyculture with their spatio-trophic habits.

Species Spatio-trophic habits

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Silver carp (Hypophthalmichthys molitrix)

Surface feeder - Phytoplanktophagous

Bighead carp (Aristichthys nobilis) Surface feeder - Zooplankton feeder

Catla (Catla catla) Surface feeder - Zooplankton form the major diet

Grass carp (Ctenopharyngodon idella)

Surface/column feeder - Macrophyte feeder

Rui (Labeo rohita)Predominantly column feeder - plankton and organic debris form the major diet

Thai Sarputi (Puntius gonionotus)Column/bottom feeder - Plankton and soft aquatic weeds form the major diet

Mrigal (Cirrhinus mrigala) Bottom feeder - Detritivore

Common/Mirror carp (Cyprinus spp.)

Bottom feeder - Omnivore

Stocking density

Rate of stocking generally depends on the biological productivity of a pond and the amount of supplementary feeding. In general, stocking rate is determined in relation to water surface area of a pond. A pond having an average water depth of 2.5 m may be stocked at the rate of 700–900 fingerlings/bigha.

Species ratio

Selection of species ratio generally depends on seed availability, market demand, nutrient status of a pond etc.

The following general guidelines are found to be very useful :

Six species culture system

Under six species combination the system surface feeders should form about 40–50% (catla 10–15%, silver carp 30–35%); column feeder (rui) 20–25% in moderately deep ponds (above 2 m average water depth), and 10% in shallow ponds (below 2 m average water depth); bottom feeders 30–40% (mrigal 15–20% and common carp 15–20%) and macrovegetation feeder (grass carp) 5–10% depending upon the availability of a dependable source of weed supply.

Five species culture system

In the absence of dependable source of feed for grass carp five species combination may be adopted wherein Silver carp, Catla, Rui, Mrigal, Common and Mirror carp may form 20–30%, 10–15%, 15–20%, 10–15% and 15–20% respectively.

Four species culture system

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Although silver carp grows faster and contribute significantly to the total production, due to lower price and market demand in some areas it is not a preferred species. Under such condition four species combination may be followed consisting of Catla 30–40%, Rui 20–30% in deeper ponds and 10–15% in shallower ponds, Mrigal 15–20% and common carp 15–20%.

Three species culture system

Depending upon the market demand, price and availability of quality seed, even a three species combination system consisting of 3 indigenous carp species may be followed (Catla 40%, Rui 30%, and Mrigal or Common carp 30%).

Generally all the fish species should be stocked at a time. However, it has been observed that due to some degree of inter-specific competition for food between catla and silver carp the growth of catla is affected. As such, it is recommended that silver carp should be stocked one or two months later than catla, by the time catla generally picks up good growth rate. Silver carp with its faster growth rate is able to attain over 1 kg size in 9–10 months.

It is advisable to stock the ponds with larger fingerlings of 10–15 cm size for better survival. Recent experiments have, however, indicated the possibility of high survival and production rates when stocked with early fingerlings (5–8 cm) in predator free ponds. The other advantage of using smaller size (5–8 cm) is the cheaper price.

2.3.3 Post stocking management

This phase includes the activities to be undertaken from stocking of fingerlings up to the final harvesting of fish from the pond. The activities are - manuring, feeding, growth and health monitoring, water quality monitoring, hazard management, partial harvesting - restocking and final harvesting.

Manuring

Besides, application of high dose of base manuring before stocking, regular addition of manure in small quantity is required in semi-intensive culture system in order to ensure uninterrupted propagation of natural fish food organisms in the pond.

Poultry manure or cow dung is the cheapest available source of organic manure for fish pond in rural Bangladesh. It has been observed that daily application of 8– 12 kg manure (chicken/cow-dung) in an one bigha pond is sufficient for maintaining optimum level of biological productivity in a pond throughout the culture period. However, in some ponds, it may be necessary to add some inorganic fertilizers along with the organic manure. Addition of 0.7–1.0 kg urea and 0.35– 0.5 kg TSP per bigha per week have been found good for ponds with higher density of phytoplankton feeding silver carp.

Supplementary feeding

The need for supplementary feeding in a polyculture pond depends on the intensity of fish culture. After certain level of fish biomass increase, the available natural food organisms in a pond are not sufficient to support further growth of fish. In Bangladesh, the prepared balanced fish feed are not yet. Oil cakes, rice/wheat brans, grain fodders, other agricultural by-products and available slaughter house by-products (blood, rumen content, viscera etc.) may be utilized as fish feed ingredients (Table 2.5).

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Table - 2.5 Chemical composition of generally available ingredients for fish feed (As % of dry matter)

Chemical components

Rice bran

Broken rice

Wheat bran

Mustard oil cake

Fish meal 

Fresh blood

Poultry viscera

Dry matter 91.3 88.6 90.7 90.0 86.0 20.2 26.3

Crude protein 13.7 8.5 13.9 39.0 55.6 95.7 52.9

Crude lipid 5.4 0.6 8.3 11.0 12.0 0.2 42.4

Nitrogen free extract

48.8 90.2 60.1 28.0 8.2 - -

Crude fiber 20.0 0.2 13.1 12.0 2.9 - -

Others 12.1 0.5 4.6 10.0 21.3 4.1 4.7

Digestible energy Kcal/kg

2416 3077 2995 3108 3569 36562 5508

Source: New, 1987.

Besides natural aquatic weeds in ponds, the grass carp can be fed with cut bits of soft fodder grass like napier grass and tender leaves (Fig.2.1). The best growth rate can be achieved, if fresh green feed is supplied @ 30–50% of the estimated body weight per day. The green feed should be applied inside floating frame tied to a bamboo pole so that the consumption by the fish could easily be monitored. The grass carp also eat other supplementary feed. It is more aggressive than other species. The grass carp should therefore be fed about half an hour before the application of supplementary feed to other carp species.

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Fig.2.1 Application of grass inside floating bamboo frame

For other species, suggested supplementary daily feeding rate can be 3–5% of estimated body weight of column and bottom feeders.

Feed should be prepared daily. Of the total amount of feed for the day, 50% should be mustard oil cake and 50% should be wheat bran or rice polish. The calculated amount of mustard oil cake should be water soaked overnight then the wheat bran or rice polish should be well mixed with soaked mustard oil cake and shape the feed into balls or pie form. The feed balls are then apply in one or two selected corners of the pond preferably in the morning around 10 a.m.

Storage of feed

The price of feedstuff show seasonal variation. Therefore it is better to buy a larger quantity when the prevalent price is low. However, without proper storage, the nutrient value can deteriorate rapidly. A decomposed, fungal infected feed must not be given to the fish! Feed ingredients should be stored in places which are dry and well ventilated. Feed should be stored always 10–15 cm above the floor level (Fig 2.2).

Fig. 2.2 Proper storage of feed stuffs

Pond bottom raking

In order to remove toxic gasses from the pond bottom and overall improvement of pond environment, bottom raking should be done with ‘horra’ (Fig 2.3). Horra is made up of a rope fixed with several sinks. When it is pulled, the sinks hit the surface of pond bottom and help emit toxic gases from the pond. Horra should be pulled 2–3 times a week.

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Fig. 2.3 Local made Horra for pond bottom raking

Regular sampling of fish

In a proper fish production management system, periodic sampling at regular interval is very important with a view to

checking the health condition of the fish; monitoring the growth rate of fish;

calculating the quantity of supplementary feed to be applied in accordance with the increasing biomass of fish.

estimating/survival mortality of fish in the pond

Periodic sampling of fish should be done at least once in a month. In each sampling 10–20 fish of every species should be taken for growth measurement. For sampling, complete netting of pond by seine net is better. However, partial netting of pond also serves the purpose of sampling. Effective partial netting can be done by applying feed at one corner of the pond. The feed attract most of the fish resulting in better catch and sample size.

During each sampling, data relating to fish health and growth rate has to be properly recorded (Format 3).

Any undesirable fish, if some how get into the pond, must be removed if found in the sample netting. In case some fish exhibit the symptoms of any disease, suitable curative measures should be taken immediately. However, prophylactic treatment measure such as giving the fish a dip in potassium permanganate @ 250– 500 ppm/minute should be strictly followed before releasing the fish back in the pond.

Harvesting of fish

Harvesting of fish means the complete removal of fish from the pond at the end of production cycle. A single stocking and a single harvesting are the common practice in existence in Bangladesh. However, like

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other countries, the technique of partial harvesting and restocking is now being practiced in Bangladesh and has been found to yield better results in terms of fish production per unit area. Under prevailing agroclimatic conditions and proper production management system, some species such as Silver carp, Grass carp, Mirror carp etc. attain marketable size (about 500 g) in 4–5 months of stocking. Bigger size fishes of such species should be harvested and sold in batches and the pond should immediately be restocked with the same number of fishes of such species. Benefits of partial harvesting and stocking are:

allow smaller fish to grow faster increase carrying capacity of a pond and thus the total production become higher per unit area

farmers get some cash return from the pond within a short period of 4–5 months. This encourages them to reinvest the money in improving his production capacity

all the trophic and spatial niches of the pond are fully utilized throughout the culture period maximizing production

Harvesting of fish is related to biological productivity and carrying capacity of the pond. When the pond is over crowded and the productivity of pond can not support further growth of fish biomass in manure fed pond, relatively bigger sized fishes must be harvested in order to leave available space and food for smaller fish to grow further. Thus, partial or total harvesting of fish can be done at any time when the carrying capacity of a pond is saturated.

Harvesting and marketing of fish in rural areas has to be adjusted in accordance with the market days and demand. Harvesting and marketing of small quantity of fishes by batches would ensure better price in local markets. However, one will also have to consider the cost of harvesting.

Harvesting should be done by seine net preferably in the morning when pond environmental conditions remain good and also ensures better market price of fish. During harvesting, marketable fish should be sorted out first and then small size fish should be returned to the pond. The total operation should be done as quickly as possible so that the fishes returned back to pond are not stressed.

For effective and efficient harvesting of fish from cultured pond, proper nets should be used. Nets presently used are not designed for pond harvesting, and as a result they are not very efficient. Scoop net should also be used in selecting/handling fish. Sketch of a scoop net and seine net with some modifications are suggested through the following illustrations which will help improve harvesting efficiency (Fig.2.4 and 2.5).

Handling of fish

During partial harvesting, the fish that are to be returned to the pond must be handled carefully. What to do and what not to do are listed below :

Improper Proper

Landing the total catch with net on the bank of the pond to select the fish to be removed

Carefully collect the fish from the net keeping the fish in water

Fishes are kept over crowded during the sorting process

Allow more space and do not concentrate too many fish in a small area

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Surface feeders are retained in the net while other species are selected

First remove silver carp, then catla, grass carp and sarputi, and end with bottom feeder.

The fishes which are not selected for marketing are badly handled by throughing one by one in the pond

Allow them to swim out from the net of their own.

Fig.2.4 Scoop net for easy handling of fish

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Fig.2.5 Appropriate seine net and netting for pond harvesting

The 1–1.5 inches mesh netting (2) is attached on each side at regular intervals to (1) 5–7 feet wooden poles to form a bag shape. The top of the net is mounted with floats (3) while its bottom part is mounted on a rope with fixed sinkers (not bricks) (6). Two corners are reinforced with steel tubing (4). The seine net is slowly pulled vertically along the pond bottom through two long ropes (5 and top)

Dewatering of pond is the best way of final harvesting though it is not possible regularly as most of the ponds in Bangladesh are undrainable type. Such ponds should be repeatedly netted until the maximum number of fish are harvested. The rest of the stock should be killed by applying suitable fish toxicant.

All harvesting results should be recorded (Record keeping format-4). After the final harvest the total production can be calculated easily from a properly kept recording system.

2.4 RECORD KEEPING AND ECONOMICS

Fish farmers should be encouraged to maintain proper records of their fish culture operations. The main benefit of a farm record keeping are that --

a. Such record will provide them with a means of evaluating their performance.

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b. Properly kept records will pinpoint the farmers the causes or factors responsible for their high profit levels or losses in each crop or year. Such information will provide them with a more reliable basis to make decision affecting their farm operations in the future.

c. These records can be shared with government agencies for formulating policies and development programmes for the development of fish culture in the country.

Essential components of the fish farm record keeping book

1. Basic data about the pond2. Monthly Fish Production Management Record3. Sampling records4. Harvesting and marketing record5. Economic evaluation of production6. Performance indices.

(Format: 1–6 enclosed)

FISH FARMERS RECORD KEEPING FORMAT - 1

BASIC DATA ABOUT THE PONDNAME OF FARMER :ADDRESS OF FARMER

:

TENURE STATUS :

FISH PONDArea (in bigha):Depth (in meter): Maximum:         Minimum:(with seasonal changes)

TYPE OF FISH CULTURE :(Extensive, semi-intensive, integrated, monoculture, polyculture, etc.)

POND MANAGEMENT

Pond preparation:

Method of cleaning :Date of cleaning :Lime :Basic manuringUrea :TSP :Organic :

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Stocking record of fish

Date Species NumberAverage weight (g)

Total weight(kg)

Price (Tk.)

 1000 Total

  1.          

  2.          

  3.          

  4.          

  5.          

  6.          

  7.          

Total            

FISH FARMERS RECORD KEEPING FORMAT - 2

MONTHLY FISH PRODUCTION MANAGEMENT RECORD

MONTH:                       YEAR:                      

DATE

L A B O U R E S

FISH FEED

F E R T I L I Z E R F E E D

CHEMICAL/ MEDICINE

F U E L

OTHERS

DAILY

TOTAL

TK

TYPE OF WORK

HRS

TK

NO

TK LI

ME

ORGANIC

UREA

TSP

M.Oil cake

Rice bran

Wheat bran

Blood

Fish meal

Ani.Viscera

KG

TK

KG

TK

KG

TK

KG

TK

KG

TK

KG

TK

KG

TK

KG

TK

TK

KG

TK

KG

QTY

TK

QTY

TK

TK

1                                                              

2                                                              

3                                                              

4                                                              

19

5                                                              

6                                                              

7                                                              

8                                                              

9                                                              

10

                                                             

11

                                                             

12

                                                             

13

                                                             

14

                                                             

15

                                                             

16

                                                             

17

                                                             

18

                                                             

19

                                                             

20

                                                             

…                                                              

…                                                              

31

                                                             

FISH FARMERS RECORD KEEPING FORMAT - 3

20

SAMPLING RECORD

Date

Fish Species

Average weight(g)

Estimated Estimated Biomass

Culture period(day)

Growth rate(g/day)Survival

(%)Number Kg/pond Kg/bigha

  S.CARP              

  CATLA              

  RUI              

  G.CARP              

  SARPUTI              

  MRIGAL              

  M.CARP              

  Others              

Total/Average              

  S.CARP              

  CATLA              

  RUI              

  G.CARP              

  SARPUTI              

  MRIGAL              

  M.CARP              

  Others              

Total/Average              

  S.CARP              

  CATLA              

  RUI              

  G.CARP              

  SARPUTI              

  MRIGAL              

  M.CARP              

  Others              

Total/Average              

  S.CARP              

  CATLA              

  RUI              

  G.CARP              

21

  SARPUTI              

  MRIGAL              

  M.CARP              

  Others              

Total/Average              

FISH FARMERS RECORD KEEPING FORMAT - 4

HARVESTING RECORD

FARM NAME:                                                                                        

POND NO:                   POND AREA:                                                  

Date Species Number Average weight(g)

Total weight(kg)

Price Remarks

Tk/kg Total Tk

               

               

               

               

               

               

               

               

               

               

               

               

               

               

               

               

               

               

22

               

               

               

               

               

               

               

               

               

               

FISH FARMERS RECORD KEEPING FORMAT - 5

ECONOMIC EVALUATION OF                 YEAR PRODUCTION PERIOD

A. Operating Cost    

 

    Tk.  

1. Dewatering/Poisoning    

2. Lime    

3. Organic manure    

4. Inorganic fertilizer    

5. Fish seed    

6. Fish feed    

7. Labour (cash/kind)    

8. Pond rental    

9. Miscellaneous    

10. Interest on operating capital    

 

  Total Expenses (Tk.)  

B. Sale Income    

  1. Revenue from the sale of fish    

  4. Value of fish consumed at home    

  5. Value of fish pond in kind    

  6. Other revenues incidental to production    

23

 

    Total Sale Income (Tk.)  

C.     Net Income = Total Sale Income - Total Expenses (Tk.)

 

FISH FARMERS RECORD KEEPING FORMAT - 6

PERFORMANCE INDICES

1. Production costs of fish per kg :

2. Production per bigha/year:

3. Net income = Total sale income - Total operating cost

4. Net income per bigha of fishpond =

5. Net income per kg of product =

6. Percentage return on operating cost =

24

Topic 3INTEGRATED FISH FARMING SYSTEMIN BANGLADESH

3.1 CONCEPT AND POTENTIAL OF INTEGRATED FISH FARMING

Integrated fish farming is a system of producing fish in combination with other agricultural/livestock farming operations centered around the fish pond. The farming sub-systems e.g. fish, crop and livestock are linked to each other in such a way that the byproducts/wastes from one sub-system become the valuable inputs to another sub-system and thus ensures total utilization of land and water resources of the farm resulting in maximum and diversified farm output with minimum financial and labour costs.

In a proper fish, crop and livestock integrated farming system, the possible inter sub-system interactions are - excreta and waste feed from livestock sub-system act as manure and feed for fish as well as can be used as manure for crop land. By-product/wastes of crop can be used as feed, manure for the fish pond and as feed for livestock. Nutrient rich bottom silt and water of pond can be a good source of fertilizers for the crop land. It thus appears that the different sub-systems in an integrated system are beneficially inter-linked to each other in a limited area, minimizing the production costs but resulting in a diversified outputs viz. fish, meat, eggs, vegetables, fruits, fuel wood and fodder which are the basic need of a farm family.

Fig.3.1 Interlinking in an integrated fish-crop-livestock farming system.

25

In Bangladesh 60 % of the farmers have less than 0.8 ha farm size which also limits space for taking up additional and diversified farming activities. Integrated fish farming on the other hand offers opportunity for taking up diversified farming activities with optimum utilization of available land space for food production, thus increasing household income of small farmers.

Currently, the farmers mainly practice mixed farming system, where crop/fishery/ livestock sub-systems are independent of each other.

Fish-livestock production in combination with planted crops on pond dykes could be a workable pattern of an integrated system.

The inter-linking is easy: the farm animal produce organic manure for fertilization of agricultural land and fish pond - the crops and plants provide food for animals, fish and man - the nutrient rich pond humus can provide fertilizer to the crop land.

In Bangladesh, the possibilities exist for integrated fish culture with livestock production. There are about 47–48 million cattle, buffaloes, sheep, goats and more than 90 million chickens and ducks in the country. Most of the excreta of these animals is not properly utilized and become wastes which may cause environmental pollution to some extent. If these livestock wastes could be applied in fish ponds through integrated fish farming system, fish production could be increased substantially (in optimal case 4–5t/ha/yr) without using any other fertilizer or supplementary feed for fish.

3.2 FISH FARMING INTEGRATED WITH LIVESTOCK

Animal wastes in integrated fish farming

Animal wastes and waste feed particles which enter the food web of a pond ecosystem are utilized in several ways:

As a source of nutrients required for primary production; As nutrients and organic substrates for heterotrophic micro-organisms which in turn may be

consumed directly by fish or by invertebrate fish food organisms;

Directly consumed by the fish.

26

Fig.3.2 A diagrammatic representation of the breakdown of animal manure in fish pond (after Delmendo, 1980)

values of animal wastes

Animal manures contain major inorganic nutrients (N,P,K) as well other trace elements viz. Ca, Cu, Zn, Fe, and Mg. Out of the available nutrients in fresh animal manure about 72–79% of nitrogen, 61–87% of the phosphorus and 82–92% of potassium are recovered from the feeds fed to animals which could be utilized for fish production and hence their role in fish culture is highly appreciated. Waste output in the form of

27

urine and faeces varies considerably in quantity and quality (Urine comprising about 40% by weight of the total waste excretion per day). The distribution of nutrients in faeces and urine also vary. Urine contains higher levels of nitrogen (N) and potassium (K) than in faeces. A higher level of phosphorous (P) is found in the faeces of animals except pigs which have high phosphorous in urine (Delmendo, 1980).

In integrated fish farming the poultry can provide the most valuable manure because of high concentration of nitrogen, phosphorus and potassium.

Under local conditions the quality of manure is determined by the following factors:

the time and method of storage soil or bedding material content of the manure whether the manure contains urine or not.

Storage of animal waste

Nutrient value of animal manure usually deteriorates during storage. The changes occur in all aspects of the quality (physical, chemical and biological). The loss of nitrogen is substantial. Under the prevailing climatic conditions expected loss might be more than 90%. The ammonia (NH3), nitrate (NO3) and nitrite (NO2) do simply volatilize into the air. The deterioration is faster under aerobic conditions with high temperature. It is always better to use animal wastes when they are fresh.

If the animal wastes are stored before using in the fish pond, following points are to be considered:

make storage time as short as possible; store in a container or a pit, covered with polyethylene or mud; try to store animal wastes in a cool place to avoid high temperature.

Prejudices to Fish/Livestock Integration in Bangladesh

a. Multipurpose use of wastes

Cattle and buffalo manure is widely used as fuel in the rural area. Chicken manure is also being used as fertilizer in crop land. In such cases, it has to be calculated carefully whether the use of manure in integrated fish culture would be able to produce more benefit for the farmer over its other uses.

b. Dislike using animal wastes in fish ponds

A large number of farmers in rural Bangladesh are reluctant to handle and apply animal excreta in fish ponds. Some of them also hesitate to eat fishes raised out of integrated fish-poultry farming where fish consume fresh poultry manure directly.

c. Multipurpose use of pond

Most of the ponds in Bangladesh are built for serving various social functions such as raising foundations for houses, bathing, washing, cooking and even for drinking. Adoption of integrated fish-livestock farming, is not possible in many ponds, particularly in homestead ponds, because of the use of water for domestic purposes.

28

d. Public health risks

The dangers of fish acting as vectors for human pathogens are still not clear. Public health aspects of fish produced in human wastes might be expected to be more serious than those of animal/fish integration. Researchers have made comparative studies of natural fish populations and those grown using cattle manure or effluent. Large numbers of bacteria, including potential pathogens were found in skin, gill and intestine of the fish cultured using manure or efficient; but tissues and blood appeared sterile on both groups. This suggests that the consumption of fish cultured in waters containing animal manure would not cause a health risk greater than that of fish caught from natural waters.

3.2.1 Fish cum Poultry System

General Consideration

In most of the agricultural farms, extensive fish culture and extensive poultry raising is practiced, but the two systems are not interlinked. To develop an integrated system of poultry production and fish culture, the first thing a farmer has to reorganize is the poultry raising and the stocking structure of fish. Although fish production is the more profitable component, in a integrated system the profitability of poultry sub-system (even if it is minimal) must also required to be a self sustaining activity be ensured, or, at least, the poultry sub-system must pay for itself.

The modern methods of poultry raising require sophisticated management which seems to be beyond the capacity of most of the rural fish farmers. It may be easier for a proven poultry farmer to integrated fish culture with his poultry rearing rather than a fish farmer integrating poultry raising in his fish farming system.

The Management of fish sub-system - as second consumer level - seem to be easier, as it is mainly “served” by the poultry sub-system.

Considering consumer's preference and local price structure, only three types of poultry farming is economically viable.

a. Chicken egg productionb. Duck egg productionc. Chicken meat (broiler) production in selected places

3.2.1.1 Fish sub-system in integrated farming

While designing the fish sub-system, both fish production conditions as well as the type of wastes/by-products expected from other sub-systems that are to be recycled in fish pond are to be evaluated. Except for modifications in the design to accommodate the poultry/crop sub-system, the rest remains more or less similar to normal polyculture system.

a. Size of pond

29

Considering rural conditions, mainly the smaller ponds can be used for integrated fish culture. Majority of the homestead ponds are suitable for this purpose. Generally 0.5–1.5 bigha size is easily manageable by small farmers.

b. Depth of pond

Any pond that retain 2–3 m water can be considered as suitable. However, the determining factor is the water depth in dry season. Minimum of 1.5m of water depths is essential even during the summer season. In low water depth the danger of organic over-loading is high from the poultry sub-system and that may cause fish kills in the summer months.

Fish pond management

The basic management practices in integrated fish pond are more or less similar to that of simple polyculture system.

Pond preparation, daily routines, sampling, harvesting, and health care are same as for polyculture system and have already been discussed under Topic 2.

However, fish species combination has to be adjusted according to the type of the livestock sub-system to be integrated. There should be very little or no supplementary feeding and fertilization of the pond water.

Selection and stocking rate of fish species

Considerations for selection:

The selected species should be compatible with each other The species and their combination ratio should be adjusted according to the amount of feed stuff and

manure that are expected to be made available by the other sub-system

As far as possible the species should fast growing

Selected fish should be hardy and resistant to common diseases and parasites

The species should be able to tolerate low oxygen levels and high organic content in the water.

The species combination and stocking ratio may vary according to the local requirements and possibilities. A general guideline on the fish stocking density and species ratio in an integrated fish-cum-poultry farming system is given in Table 3.2.

Table 3.2 Recommended fish species combinations and stocking in a typical integrated fish-cum-poultry farming system

Trophic niche Fish species Stocking ratio (%)Number of birds/bigha

20 50 100 140

      Number of fish/bigha

  Silver carp 35 94 210 280 385

30

Surface feeder Catla 10 27 60 80 110

             

Mid-water feeders Rui 10 27 60 80 110

  Grass carp 5 14 30 40 55

  Thai sarputi 20 54 120 160 220

Bottom feedersMirror/common carp/ Mrigal

20 54 120 160 220

Total stocking   100 270 600 *800 *1100

Fish yield to be expected (kg/bigha/year)

    200 330 500 700

* Partial harvesting and possible re-stocking is recommended.

Recommended size of stocking material

Size of the stocking material also depends upon the level of management. In a well prepared pond, fingerling of the size of 5–10 cm may be stocked. However, if the pond is not poisoned or dewatered, larger size fingerlings 10–15 cm should be stocked.

These guidelines are suitable for a semi-intensive production level, based on a poultry sub-system. If the organic waste requirement falls short of supply from the integrated livestock sub-system, stocking density of fish should be decreased, otherwise supplementary feeding and manuring would be necessary.

If the fish sub-system is supported by other by-products, or supplementary feeding, the stocking number can be increased with the species which can utilize best the added by-products/feed.

Managing proper growth rate in integrated pond

In most cases of integrated culture system the waste output from livestock component remain constant during the production cycle. While during the initial phase of fish rearing the biomass of fish is not big enough for full utilization of available nutrients. As a result, initially the growth rate of fish is high. The larger the fish, the more absolute amounts of food is required in order to sustain its potential growth and maintain its body weight. As soon as the biomass reaches the critical standing crop (the point when the food requirements of fish and the natural supply of feed are in balance) the growth rate starts decreasing and even may reach zero mark. In small scale integrated system supplementary feeding is not usually required. As soon as the sampling results show the pattern of decreasing growth, the biomass should be decreased by periodical partial harvesting.

3.2.1.2 Chicken sub-system

Background

Intensive production of broiler meat and egg is now common in many parts of the world. In integrated fish-cum-poultry farming system the birds are typically fed complete diets in pelleted or mash form and the

31

manure is used fresh or as dried poultry waste. The waste recycling is the key feature of the system, and integration of fish culture with poultry raising is one of the best ways of poultry waste management.

The digestive tract of a chicken is very short, only 6 times its body length. Therefore, some of the eaten foodstuff are excreted by the chicken before being fully digested. Research has shown that about 80 percent (by dry weight) of feed stuff is utilized and digested by the poultry, leaving 20 percent for use by the fish in the integrated fish culture system. Chickens while peaking, scatter about 10% of their food over the ground. This wasted feed is utilized directly by fish. The total protein content of dry chicken excrement can be as high as 30 percent. Usually, good chicken feed stuffs have a protein content over 18 percent (Table 3.3).

Table 3.3 Composition (%) of chicken manure from different chicken-raising methods.

ConstituentRaising above the pond/in cage

Ground raising

Sawdust bedding

Dry grass bedding

Moisture 11.4 12.3 15.5

Crude protein 26.7 21.9 22.3

Crude fat 1.7   1.7   2.3

Non nitrogenous extracts

30.6 30.0 27.1

Crude cellulose 13.0 17.2 18.7

Minerals (Ca, P, etc.)

16.5 16.9 14.1

Source: NACA, 1989.

Benefits of fish cum chicken integration

Following are some of the additional advantages when fish culture is integrated with chicken raising on/or near the pond dykes:

The direct discharge of fresh chicken manure to the fish ponds produces enough natural fish feed organisms without the use of any additional manure/fertilizer.

The transportation cost of the manure is not involved.

The nutritive value of applied fresh manure is much higher than dry and mixed with bedding materials e.g. saw dust or rice husk.

Some parts of the manure is consumed directly by the fish.

No supplementary feed is needed for the fish.

32

No extra space is required for chicken farming. Chicken sheds can be constructed over the pond water or on the dyke.

More production of animal protein will be ensured from the same area of minimum land.

The overall farm production and income will increase.

Selection of species

First of all the farmer should decide whether he wants to take up egg or meat production. Where the market chain is good for broiler it is preferred over layers because the shorter broiler production period can easily be programmed with pond culture period. On the other hand, egg production of layer chickens can start only after six months of rearing. In Dhaka and Chittagong areas where there are good markets, both broiler and layer chicken are recommended for the sub-system. In the country side, only layer chicken is suggested because of consumer preference. For the purpose of integrating with fish culture the following varieties of poultry are recommended (Table 3.4).

Table 3.4. Poultry varieties recommended for integration with fish culture

Name Type Main Characteristics

Shaver (Biman Poultry Complex, Savar)

Layer hybrid (white sussex X Rhode Island Red)

Laying capacity: 240–250 eggs/yrcolour of eggs is brownFeed: 115–120 g/day.

ISA Brown (Silver Carp Ltd., Faridpur)

Layer hybridLaying capacity: 240–250 eggs/yrFeed: 115–120 g/day

Shaver broiler (BPC, Savar)

Broiler hybridColour is white, growth:1.4–1.6 kg under 7–8 weeks. Feed conversion rate 2.3–2.5 kg feed to 1kg chicken

Housing of birds

Chicken sheds can be constructed out of locally available materials such as bamboo, wood, tin, etc. The size depends on the number of chicken and type of chicken. Floor space, nests, ventilation, temperature regulating device, dryness, light and sanitation are the main features to be considered during shed construction. Size of the house depends on the number of birds to be kept - normally 2–3 sq. ft. area is required for a layer chicken and 1–1.5 sq. ft for a broiler.

One of the main point is to make the pen as cheap as possible and simple in design. However, it should be strong enough to last at least for 3 years. Otherwise, frequent repair and maintenance will cost more. To extend the life of bamboo structure water proof painting is recommended.

Useful considerations while constructing a chicken pen:

Rectangular house has been found to be suitable from overall management point of view. Location:

33

The house should be built at the most wind protected side of the pond. Storms can cause serious damages to the structure.

If the house is constructed above the pond, it has to be carefully considered that the gap between the house floor and the pond water surface should be at least 1 foot at highest water level in monsoon period.

Structure:

Roof: Tin is the long lasting and perfect roof material. At roof design first have to calculate with the available length of tin sheets on the market. The tin roof should rest over a bamboo mat rice or rice straw mat to cut down heat inside the chicken house during the summer months.

Wall: Wall material can be bamboo mat, bamboo sticks or wire mesh. Optimal height of the wall should be 120–160 cm. If bamboo mat is used, the upper 1/3 of the walls should be left free and fitted with wire mesh for light and ventilation (Fig. 3.3.a).

If the walls are built with wire mesh and supporting bamboo stick, the lower one third of the walls should be covered with bamboo mat to give protection for the chicken and nests against bad weather (Fig. 3.3.b).

Floor: The floor of a chicken house over the pond should be constructed with bamboo splits. The gap between the bamboo splits should be wide enough (1.5 – 3 cm) to let the chicken faeces drop into the pond water below, but should not be too wide so as to cause injury to the legs of the birds.

Bridge: Should be movable in order to avoid pouching and predation. Three or four linked bamboo sticks serve well as a movable bridge for the caretaker and the chickens.

Facilities in a chicken house:

Feeders can be prepared out of tin or wood. The numbers should be sufficient to allow all the chicken to eat at the same time. If the height is too low (2 – 3 cm) the chicken will peck out too much feed.

Simple self drinkers are suggested for use. It is more hygienic and practical than open jar. Ready made drinkers from tin are available in bigger towns and cities, but home made self drinkers can be prepared easily from ordinary tin plate and empty milk powder cans. While preparing, care should be taken so that the hole in the can should be lower than the top of the plate. Simple bamboo cane should be kept on top to avoid being overturned by the birds. One drinker should be provided for every 25 chicken.

34

3.3.a

3.3.b

Fig. 3.3 a.b Chicken houses on fish pond

Laying boxes

If layer chicken are integrated with fish farming, the use of laying nests is necessary from the time the layers are 150 – 160 days old. One laying box can be used for every 6–7 chickens. Use of some rice straw on the nest is useful. Size of laying box should be 30 × 30 × 30 cm. (Fig.3.5).

35

Fig. 3.4 Design of laying boxes

Sitting bars

Fixing some sitting bars for night sleeping is recommended. Mainly in winter when cold air streams though the gaps in between the bamboo splits on the floor. The chicken sitting on the bars can protect itself from the cold by closing around its feathers. The birds are also separated from their night excreta.

Lighting

Artificial lighting is recommended for both layers and broilers. If electricity is available, one 60 watt bulb can be used for 100 chicken (detailed lighting program at page 42). In other places Harican (Kerosine lantern) lamps can be used.

Calculating the number of chicken for fish culture

A stocking density of 80–100 chicken per bigha of water surface has been found satisfactory enough to ensure good fish yield.

Chicken feed and feeding

To achieve good production of eggs or meat the chicken should be fed with balanced diet. In Bangladesh, suitable feed mixtures had been worked out which are used successfully by large scale chicken farms (Table 3.5).

The ingredients are available locally and can be mixed by the farmer. Some of the ingredients can be replaced with other (e.g Til oil cake with mustard oil cake) but the vitamin complex should not be changed or omitted. For small-scale egg production operations (50–200 birds), it is recommended that additional feedstuff which are easily found around the farm such as grass, crushed snail, kitchen waste etc. should be fed to the birds.

Table: 3.5. Recommended feed formula for layer and broiler chicken.

FEED INGREDIENTS

LAYER BROILER

36

   1. Broken Wheat 50.25 52.25 43.75 47.25 48.25

   2. Rice polish 22.00 25.0 25.0 24 25

   3. Til oil cake 10.0 11.0 12.0 11 11

* 4. Fish meal 17.0 10.0 11.0 17 15

   5. Oyster shell   1.0 7.5 - -

   6. Salt 0.5 0.5 0.5 0.5 0.5

   7. Embavit (B)0.25 (GS)0.25 (L)0.25 (B)0.25 (GS)0.25

* Should be “A” quality.

Appropriate feeding guidelines are suggested for both layer and broiler chicken in Table 3.6.

Table - 3.6 Daily ration guidelines for layer and broiler chicken

Layer Chicken Broiler Chicken

Age(weeks)

Daily Feed(g/bird)

Age(days)

Daily Feed(g/bird)

1 14 1–5 10.0

2 22 6–10 20.0

3 31 11–15 32.0

4 34 16–20 44.0

5 37 21–25 58.0

6 40 26–30 70.0

7 45 31–35 80.0

8 50 36–40 90.0

9–10 54 41–45 100.0

11–12 60 46–50 110.0

13–14 67 51–55 115.0

15–16 74 56–60 120.0

17–18 80    

19–20 88    

21–76 115–120    

Simple home made feeders and self-drinkers are suggested for use. 10–12 cm feeder length can be allowed for one chicken. The daily required feed should be given in two installments, one in the morning 8–9 am and another in the afternoon at 4–5 pm. Clean drinking water must always be made available to the birds. Lack of water, besides quickly affecting egg production, can cause dehydration, kidney damage and death.

37

Polluted water will cause various disease problems. Water from the tube-well is better than the water from the fish pond.

Important points of management

In integrated fish farming system usually smaller number of birds are used, and it is not very difficult to manage the chicken sub-system. However, the following important points should always be considered.

Food and feeding

Prepared feed, can be stored for 2 weeks in the dry season but not more than 1 week in rainy season. Correct storage of food stuff is very important (Fig.2.2). Decomposed or fungus infected feed must be avoided.

The chicken should be allowed to graze for one hour a day in the afternoon.

Food and fresh water should be kept in front of the layer, always in clean feeders and drinkers.

Feeders and drinkers must be kept clean.

Lighting program

In the laying period, addition of some artificial light after sunset can increase the egg laying capacity by 15–20%. The use of artificial light should be started from the time the birds are 150 days old. Starting with 30 minutes a day it should be increased by 30 minutes per week, until reaching 16 hours of continuous illumination. This optimal duration should be maintained till the end of the laying period.

For broiler raising, 24 hours lighting is suggested.

Intensity and continuity of laying

Laying of eggs should start when the chicken reach 150–160 days. Egg production period is about one year. After that the flock should be changed. Layer hybrids can increase the production up to 85–90 % laying rate at the beginning. Later the intensity will decrease. With proper management a 62–65 % laying rate could be achieved with the recommended species.

Ventilation

Climate in the rainy season remains too hot and humid causing discomfort to the birds. As a result, laying often goes down to 50–55 %. Practically on farm level nothing can be done except maximizing the natural ventilation. Therefore, in the summer/rainy season, provision for additional ventilation in the chicken house should be made.

Brood stage

After laying certain number of eggs, a hen may start to brood and stop laying eggs. This can be reversed by keeping the hen under light and by not allowing it to settle on the nest. In such cases, the hens start laying eggs within a few days if they are kept locked in a small wire case.

38

Health Control

Every effort should be made to ensure good health of the birds. For this quality of feed and the feeding programme must be maintained. The birds should be protected from stresses caused by changes in temperature, over-crowding, excessive noise etc. As a preventive measure strict programme of vaccination against common disease must be followed. In Bangladesh, the following vaccination programme is recommended.

Broiler Chicken

Age Vaccine

5th day BCRDV - 1 (Baby Chicks Ranikhet Disease Vaccine)

  Eye drop - one drop in each eye

20th day BCRDV - 2

30th day Foul pox - Wing webbing

Layer Chicken

Age Vaccine

5th day BCRDV - 1, eye drop

20th day BCRDV - 2, eye drop

30th day Foul pox-1, wing webbing

60th day R.D.V.1 (Ranikhet Disease Vaccine), injection

70th day Foul cholera-1, injection

85th day Foul cholera-2, injection

95th day Foul pox-2, wing webbing

120th day

R.D.V-2, injection.

In addition to vaccination programme periodic deworming of chicken should be done.

3.2.1.3 Duck sub-system

Fish-cum-duck rearing is another potential farming system for Bangladesh. Rearing ducks in fish pond has several advantages. Both the farming sub-system mutually reinforce each other.

Advantages to fish culture sub-system

Ducks are the “volunteer aerators” while swimming and chasing each other in the pond. The droppings of ducks, distributed all over the pond surface, has high nutrient value and which act

as manure and fish feed.

Spilled over duck feed are also good food for fish.

39

Advantages to duck rearing sub-system

Fish pond provide an excellent environment for duck. No additional land is required for housing ducks.

Duck can collect considerable part of their nutrient requirements from the pond by means of eating tadpoles, some miscellaneous fish, insects, snails etc.

However, the large scale intensive or even semi-intensive duck culture based on balanced feed, has not been found profitable in Bangladesh. The reasons are:

Ducklings of good egg laying species (pure Khaki-Campbell) are in limited supply. The price of balanced feed is high.

The egg price is low in rural areas where the duck egg is mainly consumed.

In most cases, the viability of fish-cum-duck integrated system depends on the success of the duck sub-system. Therefore, some technical points are detailed which are important for keeping the duck raising profitable.

There are three duck culture methods generally used for integrated fish farming:

a. Extensive raising , in which the simple, low productive local variety of duck is used just for family consumption. The ducks are given free range to search their own food from the surroundings. The living area is thus not limited to the fish pond. In this case duck sub-system hardly supports the fish sub-system.

b. Semi-intensive raising , in which the egg laying ducks are fed at the same rate as on land and kept at a relatively high density per unit of pond area. Therefore, higher amounts of manure and uneaten duck feed (estimated to be 10 %) usually fall into the fish pond and consequently higher fish yields can be obtained. However, high priced balanced feed is required to maintain the egg production resulting in relatively higher cost of production which is difficult to be compensated by the sale of eggs in rural areas.

c. Intensive raising , in which the ducks are kept at a high density in closed conditions. The wastes regularly go into the fish pond. However, high cost of infrastructure, unavailability of balanced feed on commercial scale, need for high level of hygienic conditions etc. rule out the possibility of intensive duck culture in Bangladesh presently.

Now the question arises:

Is the fish-cum-duck integrated culture profitable in rural Bangladesh?

The answer is yes; and for this the following method is recommended :

Duck rearing facilities

Most duck houses in the tropics are built on the pond dyke rather than over the pond surface since construction costs are less and management is easy. Duck houses should be built on the dyke.

40

They are simple shelters which provide shade from the sun and protection from heavy rain while allowing ample circulation of fresh air. Side curtains may be required to prevent wind driven rain. Duck houses should be built with local materials such as bamboo for the frame and bamboo matting for the roof. Ducks apparently do not like wire floors, unlike chicken. They cannot grasp the slats with their feet and their feet are very sensitive to damage. Cement floor may also lead to cracked eggs. Meat ducks may be raised on an earth floor but egg layers need dry grass or hay to keep the eggs clean and prevent from cracking.

Ducks can be fed and sheltered either on floating rafts or shift structures built over the pond surface (Fig.3.5). In both cases the faecal material and uneaten food fall directly into the pond.

The house should be well protected from predators. The height of the house should be 4–5 ft. The area of house will depend on the number of ducks to be kept. Normally 4 sft. of space is required for each bird.

It has been estimated that 30–35% of the dry feed consumed by the ducks is voided as manure and that only 50–60% of the manure goes into the pond water if the ducks are housed on the dyke. By housing the ducks over the pond the costs of collecting, storing, and transporting manure are eliminated and the potential problem of environmental pollution by the manure are solved. The fish would also be able to consume the estimated 15% of granulated feed spilled by the ducks during feeding which would otherwise not be utilized if the ducks were fed on the dyke. It may be worthwhile to construct floating resting and feeding places on the pond surface if ducks are housed on the dyke to increase the efficiency of recycling the manure and the spilled feed.

Ducks cause severe erosion of fish pond dykes by climbing into and out of the water which has two adverse effects: destruction of the dike, and increased turbidity and siltation of the pond which reduces light penetration and thus the amount of photosynthesis taking place in the water column. If the duck house is located on the dike, a ramp is required for easy access.

Fig. 3.5 Duck house on the dyke and feeding platform on the pond water

41

If the farmer want to keep the birds on the pond they should be prevented from climbing on to the dikes by providing fence all around.

Recommended duck species

The selection of species of duck is also very important. In Bangladesh only the egg layer type ducks should be selected for the purpose. The laying capacity of local variety is limited to 70–80 eggs per year.

The most potential egg layer species of duck is the Khaki-Campbell (Anas platyrhchos) duck. It has two colour variety: the white and the brown. The adult female is 1.8–2 kg while male is 2.2–2.5 kg. Under intensive rearing system they are able to lay above 300 eggs/year. Weight of the eggs vary between 60 and 70g. The female start to lay at the age of 23–26 weeks and able to continue laying until 360–380 days old. This good layer has already been introduced and adopted in Bangladesh. The recently introduced Khaki-Campbell - Bengali runner hybrid is also a good species. Laying capacity is about 230–250 eggs/year (unpublished information from Central Duck Breeding Farm, Narayanganj). But at the farmer level, the eggs production rate is not that good.

Nursing of young ducklings

Day-old ducklings require controlled environment (temperature, feed, drinking water and space) up to 2–3 weeks, after which they can be housed near the pond. During the first week, 50–55 ducklings can be reared per m2 within a heated room, with a screen floor (1–5cm mesh, 2mm gauge) to allow manure and uneaten food to fall through. Pelleted starter feed is provided in demand feeders, with clean taped water in troughs which are designed to allow access to the beak only, preventing the ducks from getting wet. Air temperature should be maintained around 30–32°c. After the third or fourth day, ducklings are released into a small enclosed pen during good weather and provided with shallow splashing pools to acclimatize them. Special care should be taken to prevent feed sticking to the heads and backs of the ducklings.

Although the duck is a waterfowl, water for swimming is not absolutely essential at any stage of duck rearing. Since ducks may not be able to swim at first, they should be allowed in shallow water for a few hours for the first few days to stimulate the development of the preen gland and allow the duckling to water proof its feathers.

Stocking density and ratio

Stocking density of duck in fish pond for optimum manuring depends on the soil fertility, average water depth and fish sub-system. Generally 70–80 duck/bigha is optimal for integrated duck-cum-fish production system. To start with a farmer should use only 25–30 ducks. With experience gained, number of ducks could be increased.

For fertilized egg production, 1 male: 5 female ratio is normal. While for commercial egg production the ratio of 1 male to 10–15 female would be better.

Duck feeds

Besides the limited amount of supplementary feed, the duck will consume frog, tadpole, mosquito and dragon fly larvae, and aquatic weeds which are generally not eaten by commonly stocked fish. With simplified semi-intensive rearing of ducks in ponds at relatively low densities, the protein content of

42

supplementary feed can be lowered from the 18–19% digestible protein (required if raised in crowded pens) to about 11–13%. Pond water also helps to reduce heat stress which enables the ducks to keep up their feed intake.

For semi-intensive duck farming systems, the following mixed feed for grower and layer ducks are found suitable.

Ingredients Grower feed (%) Layer feed (%)

Crushed wheat 35.0 25.0

Wheat bran 25.0 25.0

Rice polish 13.75 25.0

Til oil cake 16.0 12.0

Fish meal 8.0 8.0

Oyster shell 2.0 4.75

Embavit 0.25 (GS) 0.25 (L)

Price of 1 kg feed 8.5–9.0 TK 8.0–8.5 TK

(1991)    

Feed/day/duck   125–130 g

However, in fish-cum-duck rearing system where the ducks gather some of their food from the pond, simpler and cheaper duck feed can be used, as follows

Wheat bran 60 %

Rice polish (not rice bran)

30 %

Til oil cake 10 %

1 kg feed price (year around)

  3.5 – 4 TK

Giving 50–100 g crushed fresh snail daily is highly recommended. Duck weed (Lemna minor) is also preferred by ducks. Daily 125–130 g supplementary feed per duck seems sufficient for the adult layers when they have enough natural feed in the pond.

Ducks prefer wet mash due to the difficulties in swallowing dry mash. Initially the duckling should be fed 4–5 times a day. Later it can be decreased until twice a day. For adults 10cm feeder length can be used for each duck. If feeding on the pond is not possible then drinkers should be placed next to the feeders. Feeders and drinkers should be cleaned every day and dried to prevent from contamination. In daily feeding, it is better to feed the ducks by the same person.

43

Other useful information

Since all breeds of ducks lay either at night or early in the morning, usually before 9:30 AM, ducks should be confined in the duck house until the sun is well up and laying is completed. Ducks only in exceptional cases, lay eggs during the day time when they are in and around the pond.

Diets containing a large proportion of paddy/rice were found to be unsuitable for high yielding Khaki-Campbell type ducks which had access to little extra food from the pond.

Duck prices vary from place to place. However, prices of different sizes of ducks of two preferred varieties are given below :

Age (day)Price (Tk.)

Khaki-Campbell Peking Duck

Day old 8 10

2–28 20 30

29–41 25 40

42–70 40 50

71–90 50 60

91–100 60 75

101–126 80 90

127- 100 125

Source: Central Duck Breeding Farm Narayangonj

Diseases

Duck diseases are similar to chicken but ducks are more resistant to most common diseases. However, vaccination against some of the common epizootics should be done.

Fowl cholera:

First vaccination at the age of 6 weeks followed by once in every 6 months.

Duck pleague:

Only one vaccine at the age of 7 weeks

3.3 RECORD KEEPING AND ECONOMIC EVALUATION OF INTEGRATED FISH-CUM-POULTRY/DUCK FARMING

44

Record keeping on poultry and fish production sub-systems need different type of formats (Page 22–26) but the final economic evaluation should be prepared together in one format (Format-4).

For poultry sub-system, three separate formats are required:

1. Monthly Poultry Management Expenditure Record2. Daily Egg Laying Record3. Income from poultry sub-system

POULTRY MANAGEMENT RECORD KEEPING FORMAT 1

MONTH: ------------------------------------- YEAR: ----------------------------------------

Date

Labourers

Poultry house

Feeders/drinkers

Chicken/duck

Feed

Medicine

Electricity

Others

Daily total

Hrs. Tk. Tk. Tk. No. Tk.kg. Tk.

Qty Tk. Tk.Qty. Tk.

Tk.

1                  

2                  

3                  

4                  

5                  

6                  

7                  

8                  

9                  

10                  

11                  

12                  

13                  

14                  

…                  

…                  

…                  

31                  

Monthl                  

45

y total

POULTRY MANAGEMENT RECORD KEEPING FORMAT 2

DAILY EGG LAYING RECORD

DAY M O N T H

  JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

1                        

2                        

3                        

4                        

5                        

6                        

7                        

8                        

9                        

10                        

11                        

12                        

13                        

14                        

15                        

16                        

17                        

18                        

19                        

20                        

21                        

22                        

23                        

24                        

46

25                        

26                        

27                        

28                        

29                        

30                        

31                        

TOTAL                        

LAYING %

                       

POULTRY MANAGEMENT RECORD KEEPING FORMAT 3

INCOME FROM POULTRY SUB-SYSTEM

Date Eggs sold Broilers sold Chicken/duck sold Total

No. Tk. No. Kg Tk. No. Kg Tk. Tk.

1        

2        

3        

4        

5        

6        

7        

8        

9        

10        

11        

12        

13        

14        

15        

16        

17        

18        

47

19        

20        

21        

22        

23        

24        

25        

26        

27        

28        

29        

30        

31        

Monthly total

       

To help calculate the net profit of the system a sample (format-8) is shown as an example.

Production conditions: - 1 bigha pond area with 2–2.5m water depth- 100 commercial layer hybrid on pond fed with locally mixed balanced feed- no manuring and supplementary feeding for fish

FORMAT-4 : ECONOMICS OF FISH-CHICKEN FARMING/BIGHA

A. Operating Costs

Fish sub-system

Species Number % Cost (Tk.)

Silver carp 400 40 80

Catla 100 10 100

Grass carp 50 5 50

Rui 150 15 30

Common carp 100 10 50

Sarputi 100 10 50

Mrigal 100 10 20

Total fingerling 1000   380

Poison 500

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Lime 200

Fertilizer:Cow dung 200

Urea 30

TSP 20

Netting charges 500

Pond rental cost 2,000

Fish total 3,830

Chicken sub-system

Chicken cost (105 bird) 10,500

Annual depreciation of chicken house 1,600

Feed (8.5 Tk/kg) 37,230

Labour 3,210

Contingencies 1,000

Chicken total 53,540

Interest on working capital (12%) 6,885

Total Operating cost 64,255

B. Sale Income

1. Sale of fish (550 kg × 35 TK) 19,250

2. Sale of eggs (65% laying rate) 59,250

  (23,700 × 2.5* TK)  

3. Sale of 100 hen 6,000

Total sale income 84,500

C. Net profit (B-A)20,245

  Return on total operating cost (%) 31.5%

* Year around price in Dhaka and Chittagong. In rural area 20% less.

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Topic 4HAZARD MANAGEMENTIn Bangladesh, like other tropical countries, the overall conditions are in favour of pond fish culture. Long summer and monsoon in association with lengthy and bright sunshine accelerate good growth of fish under semi-intensive culture system. However, there are also some common problems and constraints that often hinder fish production. Some common hazards of fish culture are described here with possible means of prevention and remedy. Some common hazards of fish culture and their possible solutions are considered below.

4.1 OXYGEN DEPLETION

Dissolved oxygen level is one of the most important production factor in fish culture. Loss of fish due to reduction in dissolved oxygen content of water is not uncommon in fish ponds of bangladesh. Low level of dissolved oxygen decrease appetite and growth rate of fish. Repeated exposure to low dissolved oxygen make the fish susceptible to diseases. Oxygen deficiency appears as frequent hazard factor when the intensity of fish production increased.

Influence of dissolved oxygen levels at different concentrations on warm water fishes are given in Table-4.1

Table 4.1. Influence of dissolved oxygen at different concentration

Dissolved Oxygen

Effect on fishes

<1 ppmLethal when exposed longer than few hours

1–5 ppmFish survive but poor reproduction and

 slow growth under continuous exposure

50

> 5 ppm Normal growth and reproduction

Lethal concentration of dissolved oxygen for some common culturable species of pond fish in Bangladesh is given in Table 4.2.

Table 4.2 Lethal concentration of dissolved oxygen for some common culturable fishes (Doudoroff and Shumway, 1970)

Fish species mg/l

Catla catla 0.7

Labeo rohita 0.7

Cirrhinus mrigala 0.7

Hypophthalmichthys molitrix 0.3–1.1

Ctenopharyngodon idella 0.2–0.6

Cyprinus carpio 0.2–0.8

a. Accumulation of organic matters

In some ponds high concentration in detritus can accumulate because of reasons such as over manuring, direct inflow of community waste water etc. In all cases, the increase in organic detritus is followed by an increase in heterotrophic bacteria which also is an oxygen consumer. Usually during day time enough oxygen is produced by photosynthesis to balance the demand but during the night the oxygen reserves in the water are depleted and fish die before sunrise.

Prevention

by using proper combination of fish species under polyculture system. continuous use of bottom rakers (horra) throughout production cycle in ponds with high detritus

level.

b. Algal bloom

Because of intensive manuring and excessive use of chemical fertilizers planktonic algae are often over produced. In this “deep green” water the light penetration is limited to a thin surface level. When the day is calm, dissolved oxygen level in the surface water is very high (above 100% saturation), while the oxygen balance is negative in deeper layers. In windy days, the oxygen from the upper level is mixed with the oxygen poor water of deeper levels. Thus making enough provision of oxygen for night time respiration. But if the night is warm and calm oxygen deficiency will often occur before sunrise.

Prevention

By using higher number of silver carp in the fish stock the danger of phytoplankton bloom can be considerably decreased.

51

By daily monitoring of water colour and use of fertilizer. When the symptom of algal bloom appears, fertilization should be stopped for some days.

c. Cloudiness:

Cloudiness over a period of 2–3 days reduces light irradiation considerably. As a result the production of dissolved oxygen through photosynthesis is also considerably reduced. This factor can cause problems during monsoon months.

Steps to prevent fish mortality by anoxia

With the appearance of the signs of potential causative factors (algal bloom, calm evening etc.) the pond should be checked during the second half of the night. When the symptoms of oxygen deficiency start (gulping of fish). The following actions should be taken immediately.

Splashing the water surface with bamboo poles. Add fresh water by pump from neighboring water body or circulate the pond water. Let the water

splash as it enters the pond.

Stop or minimize manuring on cloudy days.

4.2 EMBANKMENT PROBLEMS

a. Traditionally the slopes of fish ponds are prepared too steep. The slope should be at least 1:2. Old construction should be strengthened at the weak points from time to time. The best solution is to make a fence by bamboo poles on the original embankment and fill the collapsed part with compressed dry soil. As soon as possible plant grass on this part to avoid erosion. Leakages and possible connections with other water bodies must be stopped. The above mentioned method can be used with some soil filled bag also.

b. Cultivation (horticulture) on embankments should be limited to the top. The sides and 1–2 feet on the brink of embankment should be kept for grass to stop soil erosion.

Decomposing roots of dead or cut trees also create holes in the dike which can cause erosion. These holes should be closed with soil.

4.3 POUCHING OF FISH

In some places this problem causes more damage than other, hazards. Some suggestions which may give some protection beside proper guarding:

Putting bamboo twigs or branches of trees in the water along the dike sides, closely blocking the use of nets.

Fixing barbed wire under the pond surface in criss-cross manner is fairly effective.

Fencing the farm/fish pond properly.

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4.4 PREDATORS

Snakes and birds can cause problems in fish ponds by feeding on fingerlings. Chicken/ducks are often attacked by wolves and jackals.

Protection

Chase away predatory birds from pond. Put poison injected eggs on the embankment to kill predatory birds. Destroy the nests of fish-eating birds near the pond site. Collect the eggs from the poultry house several times a day. The bridge should be removed from the poultry house at night. Keep guard dogs to protect chicken/ducks at night time.

4.5 AQUATIC VEGETATION

Aquatic vegetations in ponds whether floating, sub-merged or emergent inhibit fish production when they are in excess. They absorb nutrients from pond soil and water and hinder production of fish food organisms in ponds, hinder easily movement of fish in ponds, absorb oxygen at night causing anoxia, prevent penetration of sunlight to pond water, shelter fish pathogens and make harvesting difficult.

All aquatic vegetations are to be removed manually from the pond at the time of pre-stocking management. These vegetations, however, can be used favourably in fish culture as valuable manure. Some grass carp can be stocked to keep control of excessive growth of aquatic vegetation.

4.6 FLOOD

One of the major hazard to pond fish culture in Bangladesh is the recurrent flood. Every ear, a considerable number of ponds get inundated with flood water. During inundation, most of the stocked fish get away from the pond and at the same time predator and weed fishes enter into the pond and thus the farmers are discouraged to take up pond fish culture in many areas of the country.

To protect the pond from flood, pond dykes if possible, should be raised high above the flood level or some changes have to be made in stocking and harvesting schedule viz. ponds in flood-prone areas are to be stocked with large fingerlings immediately after possible flood period (Sept.-Oct.) and harvested before the next possible flood (June-July).

4.7 WATER LEVEL FLUCTUATION

Many ponds completely dry up in summer season (seasonal pond). If there is any such possibility, the water level should be maintained above four feet. Pumping water from shallow tube well or nearby water source could be a solution. But most of the rural ponds do not have this facility. In these ponds, the production can be maintained with proper management especially by stocking the ponds with fish as soon as water level increases and harvest them before the water level goes down too low to become risky for fish production. Repairing and strengthening of dikes are necessary before the monsoon starts.

53

4.8 FISH DISEASES AND DISEASE CONTROL

Outbreak of fish diseases in most cases originate from management mistakes such as --

over fertilization overstocking giving substandard/contaminated feed (mouldy, rotten) or in insufficient quantity stress, rough handling at netting etc.

Diseased fish can be detected by their unusual behavior and appearance of some clinical and sub-clinical symptoms.

Warning symptoms in pond are:

the fish staying at the surface of the pond water gulping at the surface of the water irregular swimming loss of appetite mortality of several fish of the same species with similar symptoms erosion of skin and fins damaged or puffed scales haemorrhagic spots on skin haemorrhage or discolouration of gill puffed, soft belly puffed, soft belly + discharge from anus exophthalmia (pop eye) lesions and deep ulcerations excessive mucus secretion and appearance of discoloured patches over the body

Some common diseases of fish and their symptoms and treatment measures

DISEASECAUSATIVE AGENT

COMMON SYMPTOMS

TREATMENT MEASURES

Bacterial disease:    

Bacteriemia (Haemorrhagic septicaemia)

Aeromonas hydrophila, Pseudomonas fluorescens and possibly others

Shallow ulcerations, haemorrhages and in severe cases the abdomen is swollen and the scales protrude. Internally the body cavity is filled with opaque fluid, and sometimes haemorrhages over swim bladder.

Over crowding, and oxygen depletion are some of the contributing conditions that must be avoided. Terramycin (oxytetracycline) with feed @7.5 g/100 kg body weight/day for 10–12 days. Furazolidone @5–7.5 g/100 kg body weight/ day for 2–3 weeks. Pond treatment @3–5 ppm of potassium

54

permanganate is also a practical approach.

Columnaris disease

Flexibacter columnaris

Lesions on the head, back and gills. The lesions start as small raised whitish plagues with a reddish peripheral zone and develop into large haemorrhagic ulcers.

Dipping in 500 ppm copper sulphate for 1–2 minutes; Adding chloromycetin @5–10 ppm to pond water; Terramycin with feed @75 mg/kg fish/day. Pond treatment @2–4 ppm potassium permanganate.

Fungal diseases:    

Saprolegniosis Saprolegnia spp.    

   

Ulceration of the skin, fin erosion, exposure of muscles and jaw bones and in some cases tufts of minute white hair like outgrowths may occur in the affected regions.

Dip treatment in 3% common salt solution or in 500 ppm copper sulphate solution or in 500–1000 ppm of potassium permanganate solution. Swabbing with 10,000 ppm of potassium dichromate is also recommended.

BranchiomycosisBranchiomyces spp.

Characterized by necrosis in the gill due to intravascular growth of this fungus. Histologically hyperplasia, fusion of gill lamellae and areas of acute necrosis are seen.

Improvement in water Quality, avoidance of over feeding and manuring; and addition of freshwater are quite effective. Draining and liming the pond or treatment with bleaching powder is essential before initiating the next culture operation.

Myxosporodiasis Myxobolus sp.

Presence of white cysts of varying diameters on the body, fins, gills, opercula etc. In some cases, emaciation, dark colouration together with presence of cysts and spores in kidney tissues without showing external cysts.

Infected fish should be immediately removed from the pond. Before initiating the next culture operation the pond should be dried if possible and/or thoroughly disinfected with bleaching powder @50 ppm. Provision of settling tank before the water intake in the pond also reduces the risk of infection.

Metazoan diseases:    

Monogenetic Trematode

Gyrodactylus sp. and

Heavily infected fish show increased

Bath in 100–250 ppm of formalin ranging from 1 to 3

55

infection Dactylogyrus sp.

production of mucous, frayed fins, skin ulcers and damaged gills, Microscopic observation of the skin temporary mount of a portion of gill show the presence of the parasites.

hours, is very effective, Dip in 2–5% salt solution till the first sign of distress is equally beneficial. Bath or pond treatment with some soft organophosphorus insecticide (Malathion and @ 0.25 ppm in pond) lesion/smear is also equally effective.

Black spot disease

Diplostomum sp.

Development of small black or brown spots on several parts of the body and fins. Microscopic examination and dissection helps in locating rolled up and slowly moving worms embedded in the connective tissues.

Fish exhibiting black spots may be given an hour bath in 10 ppm picric acid solution. Removal of aquatic snails and preventing the entry of birds are some of the preventive measures. Infection does not spread from fish to fish and hence it is not worth treating infected stock.

Argulosis Argulus sp.

Development of haemorrhagic patches over the body and presence of the parasite in large number in and around the lesion.

Benzene hexachloride application in pond @0.02 ppm with a second subsequent treatment after a week. Affected fish should also be given dip in 500–1000 ppm potassium permanganate solution which helps in avoiding secondary infection as well as accelerate the healing process. Malathion @ 0.25 ppm in pond also effectively controls the infection. Malathion also requires a second treatment after a week interval.

Lernaeasis Lernaea sp. Anaemia, severe ulcerations and presence of attached cylindrical parasite of 1 to 2 cm length hanging outside. Sometimes causes mass mortality in carp nursery and rearing ponds.

Baths in concentrated solution of salt and potassium permanganate is reported to be effective. However, the author has found very little improvement by potassium permanganate treatment. Juveniles are embedded in the skin and hence remain unaffected. Bromex completely cures the infection

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when applied @0.15 ppm.

Leech infection Piscicola sp.

They are not very dangerous. They affect the fish by their attachment and feeding. Area of attachment normally exhibit excessive mucus production, and some signs of haemorrhages. Open wounds are often infected by bacteria and fungi, Attacked fish show attached parasite, irritation and restlessness.

Removal of aquatic vegetation and maintenance of pond hygiene is the most important preventive measure. Hard objects such as stones, logs etc. should also be removed. Disinfection of pond with unslaked lime @ 250–300 kg/ha should be done prior to next rearing operation, Short bath in 3–5% salt solution is very effective treatment.

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