“Freshwater Aquaculture”(FAC-211)

Books1.Hand book of fisheries and aquaculture.(ICAR book by Dr. S. Ayyappan)2. Freshwater Aquaculture (By R. K. Rath)3. Aquaculture : Principles & Practices (By T.V.R. Pillay)

Cultivable fish species

• Carps, catfishes, prawns and mussels.

• Diverse to suit varied ecological conditions of different water bodies as also to meet the regional preferences.

•Technologies available for breeding and culture of air breathing (Clarias batrachus, Heteropneustes fossilis) and non airbreathing catfish (Wallago attu, Mystus seenghala, M. aor and Pungasius pungasius) 

• FW prawn Macrobrachium rosenbergii and M. malcolmsonii imp. For hatchery and grow out system.

• Culture of FW pearl through nuclei implantation in the bivalve, Lamellidens spp.Recently chinese large bivalve Hyriopsis introduced for pearl culture.

•Cultivation of aquatic weed makhana, Euryale ferox and water chestnut, trapa bispinosa, blue green algae spirulina spp. And biofertilizers like Azolla and duckweeds Lemna, Spirodela, Wolfia etc useful in waste tr 

Coldwater aquaculture

• Cultivable fish species are Trout (Brown & rainbow trout), Indian trout (Schizothorax spp), Mahseer, Common carp including mirror carp among cyprinidae.

• Modern trout farms in India – Himachal Pradesh trout farm, J & K trout farm.•Mahseer breeding.

 

• The potential cultivable species have gained importance due to excellent food value, delicious taste, better meat quality and consumer preferences.

Water resourcesPonds & tanks – 2.25 million haBeels & derelict waters – 1.3 million haLakes & reservoirs – 2.09 million haIrrigation cannals & channels – 0.12 m KmPaddy field – 2.3 million haConsidering the availability of water area of ponds & tanks only 45% utilized shows the potential of horizontal expansion

Fish production

• FW aquaculture account over 70% of total inland fish production.

• Both Indian and exotic carp contribute over 90% of total freshwater aquaculture production.

•FFDAs enhanced the average productivity from 500 to about 2000 Kg/Ha/yr however the potential of technologies at 15 tonnes/Ha/yr.

Sl. No. Culture system Average production rates (T/ha/yr)

1 Composite fish culture 4-6

2 Intensive culture 10-15

3 Clarias culture 3-5

4 Sewage-fed fish 3-5

5 Integrated fish 3-5

6 Pen culture 4-5

7 Cage culture 10-15

8 Running water fish 25-50 kg/m3

9 Shrimp farming 2-5

10 Aquatic weed based 3-4

11 Biogas slurry based 3-5

12 Makhana & air breathing fish 1.52 + 94 kg makhana

Fish production range under different culture systems

Azolla

Lemna Spirulina

FW mussel

Makhana (Euyale spp.)

Cage culture

Mud Crab Pen

Culture of Indian Major CarpsManagement of Nursery Ponds

Pond may be either existing one or newly constructed

Pond Preparation

The shape of pond must be rectangular and pond direction should ne east to west. Size of pond should be 0.03 to 0.05 ha with water depth of 1 to 1.5 m. There should be screen at inlet and outlet. It is necessary to expose pond bottom to the sunlight for better mineralization, escape of toxic gases and to keep free from aquatic insects, aquatic weeds, predatory fishes.

Steps (Pre-stocking)

1.Eradiation of aquatic weeds.

2.Removal of unwanted fish.

3.Application of lime.

4.Fertilization.

5.Control of aquatic insects.

1. Aquatic weeds

It is defined as unwanted and undesirable vegetation that grow in waters and if unchecked causes serious problems in fish culture.

Based on the habitat, classified into floating, submerged, emergent, marginal, filamentous and algal blooms.

a. Floating weeds – Don’t have roots, they may be floating in water with leaves over surface of water, drifted by water currents and waves induced by winds. They are more problematic than the other kind of weeds. Eg. Eichhornia (Water Hyacinth), Pistia (Water Lettuce), Salvenia (Water Fern), Duck weed (Lemna, Azolla, Spirodella)

b. Submerged weeds – Present in water column and not seen above water surface, some are rooted at the bottom of the ponds while some are non-rooted. Rooted weeds – Hydrilla, Vallisneria (Tape grass), Potamogeton, Otelia, Najas, Chara (Stone wort), Non-rooted – Ceratophyllum, Utricularia

c. Emergent weed - Rooted at the pond bottom but leaves are floating above surface of water. Eg. Nymphia, Nelumbo, Nymphoides, Myriophyllum.

d. Marginal weeds – They are grown at edge of ponds or at interphase between land and water, grow over moist land. Eg. Typha, Marselia, Cyperus.

e. Filamentous algae and algal blooms – Scum or mat forming type and found floating at pond surface. Eg. Spirogyra.

Algal blooms are formed by unicellular algae. Eg. Microcystis, Euglena.They are formed due to over fertilization or due to input of excess nutrients.

Disadvantages of aquatic weeds

• Interference in culture activities.

• Decrease in DO level

• Restrict space for movement of fish.

• Utilize nutrients.

• Interference in netting operation.

• Restrict light penetration.

• Release toxic gases.

A balance biomass of submerged vegetation and algae is required for ecosystem of composite fish culture but excessive infestation is harmful.

Control of aquatic weeds

Generally the method is selected based on the dimension of the weed infestation, size of the pond and time available.

1. Physical- manual or mechanical, various tools such as sickle, blades, wire mess, hooks, wooden sticks, weed cutter etc. are used.

2. Biological- stocking of weed-eating fishes like grass carp, common carp, gourami and silver barb is an effective method for long term control and maintenance of weed population especially in grow-out.

3. Chemical or weedicides- Marginal & emergent weeds by spraying glyphosate@3 kg/ha, foliar spray of 2-4D @ 7-10 kg/ha, phytoplankton bloom by algicide Somazine or Diuron at 0.3 to 0.5 ppm. Anhydrous ammonia @ 20ppm N is also effective not only in controlling the submerged weeds but also helps to eradicate weed & predatory fish.

Strategies for development

Fish feed pellets

Young fish

Fish harvest from a cage

Harvesting fish from a pond

Strategies for development

Ornamental fishesgoldfish

Marine AlgaeWorld farmed harvest in 2004 – 16,225,410 MT

China harvested 71% of total

Algae farm

Cultivated kelp

Sushi with black algae wrapper

Pearl Oyster

Japan is the leading producer of pearls

Inserting a nucleus

Removing a pearl

1. Application of modern aquaculture techniques.

2. Introduction of new cultivable species.

3. Improvement in fish feed.

4. Improvement in the quality/availability of seed

5. Aquaculture practices in unutilized water bodies.

6. Increase the no. of hatcheries.

7. Culture of prawn, aquarium fish, FW pearl production etc. should be emphasized.

8. Improvement in the existing extension practices.

9. Human resource development in fisheries sector (fishermen/fishfarmers, entrepreneurs etc.)

10. Improvement in the fish marketing and processing.

Strategies for development

Soil & water characteristics

The productivity of a fish pond depends on the physical, chemical and biological properties of the pond soil. Pond bottom acts as the laboratory where process of mineralization of organic matter takes place and nutrients are released to overlying water column. Physical properties of soil like texture and water receptivity, and chemical properties like pH, organic carbon, available nitrogen and available phosphorus are important parameters which require considerable attention for effective pond management.

Slightly acidic to neutral soil with pH 6.5 to 7 is considered productive. Since low soil pH is associated with low productivity, pond bottom with low pH needs correction, done through lime application.

In acid sulphate soil, the high levels of pyrite (FeS2) present in the soil remains reduced and undergo little changes as long as the soil is submerged and anaerobic. When soil is exposed , aerobic condition helps in oxidation of these pyrites resulting in formation of suphuric acid, which mixes with water in the pond and reduces its pH. Correction of soil involves, repeated drying and filling to oxidise pyrite, filling with water and holding till water pH drops to below 4 & draining of pond.

Lime requirement during soil treatment

Soil pH Ag. Lime CalciteCaCO3

Dolomite (CaMg (CO3)2

Hydrated Lime Ca (OH)2

Quick limeCaO

6.5 2.8 2.8 2.8 4.2 2.3

6.0 5.5 5.6 5.7 8.5 4.6

5.5 8.3 8.4 8.5 12.7 6.9

5.0 11.1 11.1 11.3 17.0 9.2

4.5 13.9 13.9 14.2 21.2 11.5

4.0 16.6 16.7 17.0 25.5 13.8

% efficiency 90.2 89.7 88.3 58.9 108.5

Similarly alkaline pH in pond water is corrected through gypsum (CaSO4) and alum (Al2(SO4)3 . Liming is also done as a disinfecting agent in pond with neutral soil pH and for correction of water pH or control of turbidity in subsequent period of culture operations. Quick lime is preferred during pond preparation for its quick and caustic action, while calcite and dolomite are used for treatment and pH correction of pond water during culture operation.

Amount of lime required X 100Kg

Soil & water Quality Management

Site characteristics like porosity, acidity, and high organic matter content of bottom soils encountered during culture operations.

Drying of pond bottom to crack between crops helps in aeration, which enhances microbial decomposition of soil organic matter. The porosity of the pond bottom is corrected through bentonite, lining with plastic sheet at 0.3 to 0.5 m depth and heavy doses of organic manures (cattle dung at 10,000 to 15,000 Kg/ha/year).

The water quality parameters required for optimum growth of carps are pH 7.5-8.3, temp. 27-32oC, DO more than 4 ppm, total alkalinity of 80-200mg CaCO3/L, secchi disk visibility of 25-30 cm, total inorganic nitrogen 0.5 to 1 mg/L and phosphorus 0.2 to 0.3 mg/L. Variation in these water parameters occur in culture pond and need periodic correction/management measures.

Soil & water Quality Management

Lime helps in improving alkalinity, hardness, controlling turbidity, and reduces H2S build-up. Dolomite is particularly useful when augmentation phytoplankton growth is required.

Aeration, a proven method for improving DO availability, also helps in mineralization process reducing organic load.

Water exchange helps in reducing metabolic load. Addition of water into pond, particularly during winter, helps in improving temperature regime & prevents temp. stratification.

Turbidity with suspended soil particles can be controlled by cattle manure (500-1000kg/ha), gypsum (250-500kg/ha) or alum (25-50kg/ha).

Ammonia load in pond can be reduced through healthy growth of phytoplankton or aeration.

The H2S build in pond can be subside through frequent water exchange.

Water Quality Management in AquacultureBasic requirement of fish culture, offers favourable environment for

growth, respires with DO and get food suspended in water.

Fish Culture is influenced by various physical, chemical & biological properties of water.

Temperature- fish can perceive a small change less than 0.10C. IMC thrive well in 18-380C. Max. temp. in afternoon and min. in morning. Higher temp. reduces the DO level.

pH- Indirect measurement of hydrogen ion concentration in water, less than 4 only CO2 is absent between 7 to 10 only bicarbonate are present , and at 11 only carbonates are present, fish die at pH 11, diurnal fluctuation is because of CO2 conc. Used in photosynthesis.

DO- Most imp. For survival of fish, gill is the site for exchange of oxygen, reduction in DO reduces metabolism & restricts development & growth, sources are photosynthesis & dissolution from atmosphere, opt. 5-12ppm, loss of DO because of respiration, decomposition, mineralization of organic matter and direct loss to atmosphere. DO can be improved by adding water, recirculation, use of aerators, KMnO4, and beating water surface by sticks.

Aquaculture

Aquaculture is the farming of aquatic plants and animals in controlled environments. Finfish and shellfish are grown in artificial containers such as earthen ponds, cages and concrete or fiberglass tanks. The cultured organism is reproduced and offspring raised in captivity. The young organisms are stocked at a known density and fed a nutritionally complete diet to maximize growth rate. Water quality is monitored to maintain a healthy environment. Animals are harvested with nets when they reach market size.

Aquaculture includes culture of fish, crustaceans, mulluscs etc.

Types 1. Freshwater includes cold water fisheries

2. Brackish water- cultivation of seabass, mullets, shrimp etc

On the basis of management 1. Extensive

2. Semi-intensive

3. Intensive

Dissolved oxygenEstimation by two methods

1. Electrometric method (By using O2 probe)

2. Chemical method (Winkle’s method) by titration

A- 365g MnSO4.2H2O or 670g MnSO4.4H2O make it 1L by adding DW

B- 500g NaOH or 700g KOH + 150g NaI or 300g KI+10g NaN2 make it to 1L

Take sample in BOD bottle (250ml), add 1ml A & B solution, shake it vigorously to allow the concentrate to settle the ppt. of Mn (OH)2 and then add 1ml of Conc. H2SO4 then titrate it with Sod. Thiosulphate (Na2S2O3) 0.05 N normality, it is made by adding 6.205g Sod. Thiosulphate in1L DW.

Indicator- Starch (1g starch in 1L DW) + 0.5ml formaline as preservative.

Add around 3 drops of starch, blue colour appears, then titrate with Sod thiosulphate till blue colour disappears.

Calculation- DO (mg/L or ppm) = N X V X 8 X 1000/Vs

N – Normality of Na2S2O3 V – Volume of used Na2S2O3 Vol. of sample titrated

Plankton1. Phytoplanktons – Imp. Primary producers, make their food itself by

photosynthesis process, but excessive growth reduces DO.

2. Zooplantons – Zooplanktons can not make their food, take phytoplanktons and taken by fish.

Physical condition of water

Depth, Temp., Turbidity & Light Penetration

Depth – In shallow ponds, sunlight penetrates upto bottom which warm up water & facilitate increase in productivity, shallower tan 1 m gets overheated. A depth of 2 m is considered congenial from the biological point of view.

Temp – all metabolic & physiological activities and life process such as feeding and reproduction are greatly influenced water temp., also affects the speed of chemical changes in soil & water, generally DO decreases with increase in temp., it shows diurnal as well as seasonal variation, IMC thrives well in 18.3 – 37.8o C, the upper lethal temp. for air breathing fish is 39-41OC

Turbidity- may be either due to suspended inorganic sustances, such as silt, clay or due to planktonic organisms, it is important limiting factor in the productivity. Turbidity can be temporary i.e. caused by rain flood etc. or perennial. Turbidity reduces light penetration and hence reduce photosynthetic activity.

Selection of suitable site for aquaculture

It determines the feasibility of viable operation, it depends on two main guiding factors, the water retention capacity of the soil and its inherent fertility & also respond readily to organic and inorganic fertilization. Besides these there should be dependable perennial

source of adequate water supply to fill the ponds at any time of the year. Although site selection generally based on the species to be cultured & the technology to be employed.

The general considerations in selection of suitable site depends on agro-climatic conditions, market accessibility, suitable combination, protection from natural disasters, availability of skilled and un-skilled persons, public utilities, security, meteorological & hydrobiogical information about the area such as year temp., rainfall, evaporation, sunshine, speed & direction of winds & floods, water table etc. have to be examined.

Selection of suitable site for aquaculture

In case of small scale aquaculture, it is necessary to determine whether it has easy access to materials that can not be produce in the farm and facilities are available.

Inland based soil characteristics, the quality and quantity of available water and the ease of filling and drainage specially by gravity are basic considerations for freshwater farms.

Swamps, unproductive agricultural land, valleys, streams, river beds exposed into changes of water flow etc. land elevation and flood level have to be ascertained. The max. flood level in the last 10 years or the highest astronomical tide should not be higher than the normal height of dikes that has to be constructed into a farm.

Soil characteristics

Sandy clay to clayey loam soils are considered suitable for pond construction. Texture & porosity are the two main imp. Physical prosperities to be examined. Soil texture depends on the relative proportion of particles of sand, silt and clay. Sandy loam soils is considered best for diking. The size limits & some general characteristics of the soil constituents are

Soil constituents

Dia. Of particles (mm)

Gen. characteristics

Clay <0.002 Particles may remain suspended in water for a very long period of time

Silt 0.002 – 0.05 Feels smooth & powdery when rubbed with gingers

Sand 0.05 - 2 These are individual particles, feels gritty when rubbed with fingers

Sandy loam soils is considered best for diking.

Acid sulphate soil

Results from formation of pyrite, which is fixed and accumulated by the reduction of sulphate from salt water, process invilves bacterial reduction of sulphate to sulphide, partial oxidation of sulphide to elemental sulphur followed by interaction between Ferrous (Fe++) or Ferric ions (Fe+++) with sulphide & elemental sulphur. A sufficient supply of sulphate & iron, high concentration of metabolisable organic matter and sulphate reducing bacteria

Desulphovibrio desulfuricans & Desulpho maculatum in an anaerobic environment alternated with limited aeration are the factors that give rise to sulphate soils.

Basic consideration in the selection of species for culture

There can not be a universal fish species which can satisfy all the desirable qualities, but which satisfies the most can be suggested.

1. Rate of growth – fishes which can grow larger size in shorter period, because of this IMC are taken under carp culture in India.

2. Short food chain – Energy from primary producers to successive consumers are in decreasing order therefore the fish having short food chain like planktivorous are usually preferred. Eg. Silver & Catla

3. Adaptation to climate – Fishes adaptable to various climatic conditions can be cultured in many areas than fishes in particular area. Eg. Tout and Salmon cultured in Cold water opt. temp. 10-120C whereas IMC in warm water opt. temp. 26-300C. But common carp can be cultured throughout the world as it is adjusted to various climatic conditions.

4. Tolerance to the fluctuation of physiochemical condition of water – wide ranged tolerant fishes can be cultured more than narrow ranged fishes. This have great importance in intensive fish culture. Trout require DO of 9 mg/L, IMC 5-6mg/L, common carp 2-3mg/L, likewise for BW fish the euryhaline nature of fish is important.

5. Acceptance of artificial feed – In intensive culture system the natural food availability is not sufficient, therefore the fish which easily accepts artificial feed should be preferred.

6. Resistance to common fish diseases & parasites – Although the fish diseases are not uncommon, resistant fish are preferred.

7. Easily recruitment under controlled condition – To maintain fish culture as a continuous practice, the assured availability of healthy and pure seed from dependable source is imp. So the fish should breed easily under controlled conditions. So IMC & exotic carps pref.

8. Amiability to live together – More imp. In polyculture or multi species culture of fishes. Herbivorous fishes should not be cultured with carnivorous & carnivorous fishes of different groups are not cultured together likewise profuse breeding fish like Tilapia are not suitable with carps.

9. Conversion efficiency – the fish which gives more edible flesh per unit of food consumed in preferred than less ones.

10. Compatibility- The fish which are put in combination for culture should not compete among themselves for space and food.

11. Consumer’s preference – The culture practice of fish is undertaken should be in lined with local condition & consumer’s preference. Eg. Orisa & west Bengal people prefer FW fishes than marine water whereas in south people prefers marine fishes and Americnas prefer catfishes than carp.

Besides these basic considerations other considerations like scaless carp, reduced vertebrae bone, could etc. are also preferred.

Characters of culturable species of fish

The introduction focused on 6 (3IMC + 3 Exotic) carps.

Understanding the habits of fish, growth factor development, feeding & their ecological conditions is of great practical significance to fisheries production in India.

Characters of culturable species of fish1. Catla (Catla catla)– It is the fastest growing indigenous carp,

conspicuous body, large head, upturned mouth, non-fringed lips, back grayish colour, silvery on sides but tends to be dark in weedy waters, fins large, scale pink, the fish attain sexual maturity in 2nd year and ready to breed. Natural food is plankton floating on the upper surface of the water, early stage food is zooplankton but later also starts taking phytoplankton in its diet. Its capability to feed on natural organisms based on its structure of mouth, so considered as surface feeder.

2. Rohu (Labeo rohita) – Considered as tastiest among IMC, distinguished by its relatively small or pointed head or terminal mouth with fringed cover lips. Body elongated with moderately convex abdomen. Back is brownish grey. Dull reddish scales on the sides and pink reddish fins. The body is more linear than Catla. Sexual maturity is attained towards the end of the 2nd year.

3. Mrigal (Cirrhinus mrigala)– Next in importance to Catla & Rohu for culture. Linear body, small head with blunt snout, sub-terminal mouth with thin non-fringed lips, body silvery dark grey along back, fins orange tinged with black. Grows slower than Catla & Rohu. Attains sexual maturity in second year.

Characters of culturable species of fish4. Silver carp (Hypophthalmichthys molitrix)– Body compressed, scale

small, mouth sub-superior with lower jaws rather upturned, eye comparatively small situated below horizontal axis of body, gill rackers densely interlaced connected & covered with a spongy sieve membrane. Colour of body in alive condition is silvery white, dorsally dark brown.

5. Grass carp (Ctenopharyngodon idella) – Large sized, body almost cylindrical with flat head & brown abdomen, scales big, mouth in front, lower jaw shorter, eyes small, gill rackers shorter & sparse, comb like pharyngeal teeth. Dorsal fin short, dark brown back and white abdomen.

6. Common carp (Cyprinus carpio)- 3 well knows varieties are

a. Mirror carp (Specularis)

b. Scale carp (Communis)

c. Leather carp (Nudus)

Minor carps

6. Common carp – Body compressed, dorsal projection in arc shaped, round abdomen, mouth slightly downward with blunt snout and with 2 pair of barbles, on upper jaw lower pair a little longer. Long dorsal fin scales thick and big colour of body in alive condition usually dark grey or yellowish brown dorsally, lateral golden yellow. Apex lining of caudal fin is slightly red.

1. Labeo calbasu– Commonly called as Kali Rohu. Body is bluish green, small tapering head with sub-terminal fringed lipped mouth & 4 black barbels. Dorsal fin with 12-13 branched rays. It is omnivorous, bottom feeder in detritus and animals. Maturity and breeding habits are similar to IMC. Common in Indian rivers and occasionally in brakishwater.

2. L. fimbriatus- Commonly known as Cauvery carp. Deep body, fringed lip, dorsal fin with 15-18 branched rays & presence of reddish spot in the scales of middle row. It is bottom feeder and feeds occasionally on filamentous algae and zooplankton, widely distributed in rivers of south India.

Minor carps3. Labeo kontius – Commonly called as Pig mouth carp. Deep slaty

colour, prominent snout, sub terminal mouth with fringed lower lips & dorsal fin with 12-13 branched rays. Feeds in detritus, copepodes, rotifers, algae, pieces of higher plants, widely distributed in rivers in south India.

4. L. bata – Presence of greenish iridescence at the base of scales & dorsal fin with 9-10 branched rays. It is omnivorous bottom feeder, feeds on phyto & zooplankton and filamentous algae. It is distributed in north Indian rivers up to Godavari.

5. Cirrhinus cirrhosa (white carp) – It has small head with blunt snout & thin lips. Dorsal fin is 14-15 branched rays. The first fin rays are much elongated. It has silvery body and scales with reddish dash (-) except on the abdomen. It is bottom feeder on detritus & occasionally on zooplanktons. Found in Godavari, Krishna & Cauvery.

6. Puntius sarana – It is omnivorous, feeds on detritus, filamentous algae, micro vegetation, worms, insects, gastropods. It is common in east Indian rivers.

Cat Fishes & other fishes – Wallago, Mystus spp., Singhi, Mangur, Murrels, Tilapia, Prawns & cold water (sports) fishes.

Cat FishesThe cat fishes are air breathing or live fishes. As they are capable of

directly breathing atmospheric oxygen air. They can live for a long time without water & can therefore be transported live and fresh condition over long distances. The body is without scales and each of the upper and lower jaws possesses 2 pairs of long barbels in each jaw, mouth can not be extended, having jaws with teeth. The adipose fin may or may not be present. Majority of cat fishes are predatory & cannibalistic feeding on the all pond animals including fish fry.

Wallago attu (Freshwater Shark) – Large mouth beyond the eyes, numerous teeth, absence of adipose fin, highly predatory so not suitable for pond culture.

Mystus aor – adipose fin present, 1st dorsal fin reaching to adipose fin, common in rivers and reservoirs of north India.

M. seenghala – 4 pairs of barbels, long upper jaws deeply forked caudal fin, in which upper lobe is longer than the lower moderately sized adipose fin, distributed widely in north Indian rivers.

Heteropneustes fossilis (Singhi) – adipose fin absent and rounded caudal fin, besides animals it also feeds on algae, higher plants. It is suitable for culture in swampy areas.

Clarias batrachus (Mangur) – Adipose fin absent, elongated dorsal, long anal & round caudal fin (identifying features). Dorsal fin is small, feeding habits and distribution are similar to Singhi.

Murrels (Snake headed) – Air breathing, have good demand in market, found in shallow and derelict swamp, suitable for culture in irrigation canals & derelict swamps. They have a protected breeding season. The peak breeding is associated with pre-monsoon months.

Channa marulius (Giant snake head) – Dorsal, anal fin are long & without spines. Suitable for culture in ponds along with Tilapia. The young ones of Tilapia serves as food for C. marulius.

C. striatus (stripped snake head) – Stripes are present on its body.

Tilapia (Oreochromis mossambicus) – An exotic fish introduced in India from east coast of Africa in 1952. It is characterized by an anterior spiny dorsal fin & posterior soft dorsal fin. Male is identified from female by its enlarged upper jaws. Maturity occurs even in 2 months old individuals (monosex culture can be advisable). It breeds nearly 8 times in a year, female keep the fertilized eggs guarded in its mouth, young ones acts as food for Murrels in Tilapia cum Murrel culture.

Trout – Comes in order Salmoniformes,

Charateristics are -

1. Body is streamlined and covered with scales.

2. The Head is naked.

3. Have narrow gill opening and reduced gills.

4. Adopted to highly oxygenated water and freezing temperature.

5. They have great powers of locomotion, clinging and burrowing habits

6. They have modified mouth & lips for rasping food particles within rocks, pebbles etc.

7. An adipose fin is present in addition to rayed dorsal fin.

8. The barbels are absent.

9. Trout feeds chiefly on insects, molluscs, small fishes. However they are cannabalistic.

Cold water fishes (sport fishes)

It is a river and lake fish of cold north hemisphere & got introduced to Himalayan rivers of India.

Adipose fin above posterior part of anal, pectoral fin don’s reach the base of pelvic, caudal fin emarginated, minute scales, deep brown back with sides somewhat lighter. The upper part of head and body above lateral line are marked with numerous dark spots, fins are dark.

Brown trout (salmo trutta fario)

Introduced to Nilgiris & high ranges of Kerala from north America.

It has small mouth, positioning of adipose fin above the anal & emarginated caudal fin, head and dorsal side are steel blue in colour with a reddish band along the sides, belly is light coloured. It is numerous dark spots above lateral line. The dorsal and caudal fin are marked with dark spots, other fins are slightly pinkish, sides have rainbow iridescence.

Rainbow trout (Onrhynchus mykiss or Salmo gairdnerii)

Belongs to order Cypriniformes

Tor tor (Red finned Mahseer)

It is a stout, sturdy fish, has deep body with small mouth & narrow gaps and fleshy lips, deeply notched caudal fin. Maxillary barbels are longer than rostral barbels, dorsal side is grayish green, lateral sides are pinkish with greenish gold above & light alive green. Its belly is silvery.

It is an omnivorous feeder on filamentous algae, weeds, insects etc.

It is commonly distributed in foothills of Himalaya, Bihar, West Bengal, Assam and M.P.

Mahseer

Tor putitora (Yellow Finned Mahseer)

Commonly found in streams of Himalayas, head is broadly pointed, length of head is greater than depth of body, male has enlarged lips with two pairs of barbels of equal length, the pectorals are shorter than head, caudal fin is sharply divided. It is an omnivorous feeder on filamentous algae, insect larvae, water plants.

Tor khudree (Deccan Mahseer)

The depth of body is equal to length of its head, anterior most part of body is pointed, has fleshy lips and deeply forked caudal fin. Dorsal side and areas above lateral line are black & belly is creamy yellowish white. Its feeding habit are similar to that of Tor tor.

Acrossocheilus hexagonolepis (Chocolate Mahseer)

It is a hill stream fish common in Eastern Himalayas & Assam. It has thick lips, red eyes which distinguish it from other Mahseer. Its head is higher than its width & has sub-terminal mouth, thick lips large scale, caudal fin is deeply forked with pointed lobes. Dorsal surface of body and head are green. It is omnivorous bottom feeder on aquatic weeds, insects etc.

Coldwater Fisheries

Categorization of Coldwater fishes on the basis of temperature

tolerance• The temperature tolerance of coldwater fish lies at lower levels

of the thermal scale, which is of critical significance and plays a crucial role in their dispersal in the uplands.On the basis of temperature tolerance, the coldwater fishes are categorized as-

• Eurythermal- Having broad temperature tolerance range.

Example: Schizothorax richardsonii, Cyprinus carpio and Barilius bendelisis.

• Stenothermal- Having a narrow temperature tolerance range, nearly upto the freezing point of water.

Example: Salmo trutta fario, Salvelinus fontinalis.

• Thermal range for different fishes

• Snow trout (Schizothorax spp.) 5-25°C

• Mahseer 10-30°C

• For exotic trouts 4-20°C

• For exotic carps 7-32°C

Some Important Coldwater Fishes

• Schizothorax richardsonii• Cyprinus carpio var. specularis• Cyprinus carpio var. communis• Tinca tinca• Labeo dyocheilus• Labeo dero • Glyptothorax pectinopterus• Barilius bendelisis• S. longipinnis• S. niger• S. longipinnis• Tor putitora • T. tor• T. khudree• T. malabaricus• Neolissochilus hexagonolepis

Fisheries

• Majority of coldwater fishes are caught individually by local fishermen in rivers and streams and do not form fisheries of commercial importance.

• Some fishes form the part of commercially important food fishes, dwelling in uplands.

For example: Snow trout, Tor spp., common carp, Labeo dyochelius and Labeo dero.

• Fish production in majority of hill states ranges from 20000 tonnes to 42,000 tonnes since 1996-97 to 2004-05.

• An important aspect of coldwater fish of the uplands is the opportunity the species provide for sport.

Culture of shell fishes of India

Giant river prawn (Macrobrachium rosenbergii)

It is the largest among freshwater prawn, found in all rivers of east and west coast of India and coastal areas throughout Bay of Bengal. It has long sword shaped rostrum with equal no. of teeth on both upper and lower edges. It is benthophagic omnivorous. It migrates to estuary during breeding season.

Monsoon river prawn (Macrobrachium malcolmsonii)

It is found in all peninsular rivers of India. The second cheilipedes of female are much longer and stouter than the body. It also migrates to estuary during breeding season.

FRESHWATER AQUACULTURESEED PRODUCTION AND

GROWOUT OF GIANT FRESHWATER PRAWN

Mature male & female

Seed HarvestHatchery Growout pond

Farm raised Scampi(Freshwater Prawn)

Salinity 12 ppt (10 to 14 ppt)

PRAWN HATCHERY

Different practices of freshwater aquaculture

Monoculture - it is a practice of culturing one species of fish, in this practice only one type of natural food i.e. phyto or zooplankton is utilized. Culture of Catfishes, Murrels, Trout.

Stocking density is low, overall production and net income from monoculture is less than polyculture practices.

Polyculture - It is culture of more than two species of fish at a time in pond for efficient utilization of all available food at different trophic levels and different layers of water. So as to achieve max. fish production in the shortest possible time. It is also known as Composite Fish Culture. Basic principles is that when compatible fish species with different feeding habits are cultured together they secure themselves in the most efficient manner. There is not any serious competition among the species in fact one species may be beneficial to other. The concept of polyculture originated in China where 6 species culture is more popular in Chinese polyculture system.

SEED PRODUCTION AND GROWOUT OF CARPSSEED PRODUCTION AND GROWOUT OF CARPS

Composite Fish CultureComposite Fish Culture

INDIANINDIAN EXOTICEXOTIC

Seed farmSeed farm

Growout pondGrowout pondCircular Circular hatcheryhatchery

HarvestHarvest

Silver carp – Phytoplanton feeder – Surface feeder

Grass carp – Macrovegetation – Column feeder

Coomon carp – Omnivorous – Bottom feeder

Big head carp – Aristichthys nobilis – Macrovegetation

Bream – Parabremis pekinensis – Omnivorous

These fishes are cultured to get highest fish production.

Polyculture in India

Similar species are cultured, stocked in ration of 40:20:30:10

(Surface: Column: Bottom: Grass Carp)

Stocked at the rate of 10,000/ha

IMC – Catla – Zooplankton feeder – Surface

Rohu – Phytoplankton feeder – Column

Nain – Detritus feeder – Bottom

Exotic/ Chinese Carp

Management Practices

Pond Preparation – There are various aspects in ponds preparation which should be carried out before pond is used for culture for first time & for subsequent crops. The main objective of pond preparation are to provide fish with a clean pond base & appropriate stable water quality.

1. Cleaning – During fish production cycle considerable quantity of organic waste accumulates in pond bottom depending upon the cultural practices followed. Its waste must be removed to ensure sustain fish production from the pond. There are two methods –

a. Dry method – In this method, after the final harvest the pond bottom is dried and crack developed primarily to oxidize the organic components, left over in the pond after the previous culture. The pond bottom should be dried for at least 7-10 days & the soil should crack to a depth of 2.5 – 5.0 cm. After drying the pond bottom is ploughed up to a depth of 15 cm.

b. Wet method – In this method, after the final harvest, the accumulated organic matter at pond bottom is flushed out in form of a thin slurry using a heavy duty pump.

2. Liming – Advantages

a. It corrects acidity of water.

b. It helps to raise bicarbonate content.

c. It promotes decomposition of organic matter.

d. It supplies Ca, for growth of freshwater flora, molluscs, crustaceans.

e. It helps to establish pH buffer system.

f. It utilizes the action of Sodium (Na+) & Magnesium (Mg2+) ions, due to toxic and caustic property, it helps to kill harmful bacteria.

Pond fertilization

The main objective of adding fertilizers in fish pond is to maintain the sustain production of natural fish food organisms during the entire culture period.

Types –

1. Organic fertilizers

2. Inorganic fertilizers

Pre-stocking Preparation

• Soil tests

• Pre-flooding period depend on fish species being stocked

• Water chemistry – pH– alkalinity

• at least 20 mg/L

– nutrients• nitrogen and phosphorus

Fertilization• Purpose is to promote the growth and

development of correct size and species of zooplankton prey for fish fry.

Population Trends

Rotifers Cladocerans

Copepods?

1-2 weeks 2-3 weeks

3-4 weeks

Quality Zooplankton• Species

• Size– different fish species need different sizes of

zooplankton as first prey.

Organic Fertilizers• Plant and animal materials

– zooplankton feed on organic or the bacteria/protozoa feeding on organic

• Long-term application

• Selection criteria– low carbon:nitrogen ratio– fine particle size– readily available and economical

Fertilizers Applications

• Inorganic Fertilizers– liquid

• mixed into prop wash or mixed 10:1 (sprayed)– powder

• soluble, blown onto pond surface– granular

• fairly insoluble, placed onto shallow wooden platform 1ft below pond surface

• Organic Fertilizers– apply fertilizers completely around pond edge– frequent application

Concerns Related to Fertilization

• Low oxygen levels (organic)• Costs of either the product (inorganic) or

transportation (organic)• Greater fluctuations in daily oxygen and pH

levels• Increased aquatic vegetation levels

What fertilizer to use?

• Inorganic fertilizers for immediate results

• Organic fertilizers for long-term application

• Combination of both

Inorganic Fertilizers• Limiting factor in freshwater systems is

often phosphorus– in late summer, nitrogen may be limiting

• Fast acting

• Selection criteria– adequate phosphorus and nitrogen– economical and ease of application

• Chemical designation N:P:K

Water Quality Assessment

• Daily measurement of oxygen levels

• Weekly measurements of nitrogenous variables and pH– ammonia nitrogen– nitrates

Zooplankton Monitoring

• Sample prior to stocking and every week thereafter

• Samplers– zooplankton net– tube sampler– pumps– visual

• Desirable number -> 500+ animals/gal

• Establish large populations of desirable zooplankton prior to stocking larval fish

• Maintain fertilization rates as long as water quality allows

• Difficult to manage both large populations of zooplankton and fish fry

• Assess water quality

Summary

Conclusions

• One recipe for all ponds is difficult

• Is there a marked improvement of fish production over a pond’s natural productivity?

• No need to fertilize ponds where fish are being fed.

2. In organic Fertilizers – These are simple inorganic compounds which primarily contain at least one or more elements of NPK. Commercial inorganic fertilizers used for pond culture are the same as those of agricultural crops. Due to their high solubility in water the nutrients become readily available soon after their application.

According to composition chemical fertilizers are –

a. Nitrogen fertilizers

b. Phosphorus fertilizers

c. Potash fertilizers

a. Nitrogen fertilizers – They contain nitrogen and are available as ammonium sulphate, ammonium nitrate and urea. The form of nitrogenous fertilizers are selected on the basis of acidity and alkalinity of pond soil. Nitrogenous fertilizers are particularly essential for newly constructed pond ( because organic matter is not present in pond bottom). The efficiency of N fertilizers is inhibited by phosphorus deficiency.

It is best to maintain the P:N ratio as 1:4

b. Phosphorus fertilizers – Almost all fish ponds have phosphorus deficiency. Phosphatic fertilizers are most effective & favourable for fish culture.

- Superphosphate are most suitable in water, di-calcium phosphate is partially soluble in water, rock phosphate is almost insoluble in water, single super phosphate (SSP) is extensively used and easily available, generally phosphatic fertilizers are held in soil and its action is extended to subsequent years of its application.

c. Potash fertilizers – Potassium remain available in required quantity in natural water. It is commonly available in form of Muret of Potash (K2CO3) & Sulphate of Potash (K2SO4).

The favourable action of Potassium fertilizers can be seen in ponds with low alkalinity. In general for ponds in which phytoplankton production is rather slow, this fertilizers may be applied. It also improves the hygienic condition of pond.

Advantages of applying inorganic fertilizers

1. Exact composition of inorganic fertilizers is advantageous.

2. Mineralization is very fast, giving quick effect on pond productivity.

3. Lack of pollution.

4. No BOD (Biological Oxygen Demand) is required for chemical fertilizers or in other words there beneficial effect on oxygen content.

5. Used in small quantity and applied as additive manures. Hence convenient for utilization.

Nutrient profile of some common manures & fertilizers

Sl. No. Manures/fertilizers N % P % K %

Manures of animal origin

1. Raw cow dung (RCD) 0.6 0.16 0.45

2. Pig Dung (PD) 0.6 0.45 0.50

3. Duck droppings 1 1.4 0.62

4. Poultry excreta 1.6 1.5 - 2 0.8

Manures of plant origin

1. Mustard oil cake 4.5 2.0 1.0

2. GNOC (Ground nut) 7.8 1.5 1.3

3. Mahua oil cake 2.5 0.8 1.8

Inorganic

1. Urea 43-46

2. Ammonium nitrate 20.5

Phosphatic

1. Single Super Phosphate(SSP) 16-20

2. Triple Super Phosphate (TSP) 40-45

Potash

1. Muret of Potash 48-62

2. Sulphate of Potash 47-50

• Fertilization in fish pond starts 10-15 days prior to seed stocking depends upon the nutrient status & chemical environment of pond soil.

• Proper analysis of soil & water is essential before deciding fertilization schedule.

Nutrient status of different types of soil pond

Productivity level

pH N(mg/100g of soil)

PotashP2O5 (mg/100g of soil)

Organic carbon (%)

High 6.6 - 7.5 50 6 - 12 1.5

Medium 5.5 - 6.5 25-49 3 - 5 0.5 – 1.4

Low Below 5.5 Less than 25 Less than 3 Less than 0.5

Amount of fertilizers @Kg/ha/year

High Medium Low

Raw cow dung 5000-8000 8000-10000 10000-25000

Urea 112-155 156-225 226-260

Ammonium Sulphate 225-330 - -

Calcium Ammonium Nitrate - 350-500 501-650

Single Super Phosphate 150-219 220-315 316-405

Triple Super Phosphate 54-75 76-110 111-145

Fertilization Schedule

Quantity (Kg/ha) Periodicity of application

Raw cow dung (RCD) 2000 Initial

1000 Monthly

Urea (6.5-7.5) 25 Monthly

Ammonium Sulphate (>7.5) 30 Monthly

Cal. Ammonium Nitrate (5.5-6.5) 30 Monthly

Single Super Phosphate (SSP) 20 Monthly

Triple Super Phosphate (TSP) 8 Monthly

In general

Urea = 140

Triple Super Phosphate = 60

In 4 to 6 installments

Food and Feeding Habits

The thorough knowledge about food and feeding habits of culturable varieties of fishes taken for culture is one of essential factor for successful fish farming. The food resources in ponds are varied in forms for which a judicious combination of species for rearing is essential.

The natural food of fishes is classified into 3 groups

1. Main food.

2. Occasional food.

3. Emergency food.

1. Main food – It is the natural food, which the fish prefers under favourable conditions, in which it grows best.

2. Occasional food – Food which is consumed when main food is not available.

3. Emergency food – Food ingested when preferred food items are not available & on which just survive.

According to Nikolskii, the natural food on fishes are classified into 4 categories on the basis of gut analysis

1. Basic food – which comprises the main part of gut contents.

2. Secondary food – which is found frequently on gut contents but less in quantity.

3. Incidental food – which rarely found in the gut contents.

4. Obligatory food – which is consumed in absence of basic food.

However, on basis of characteristic of diet, fishes are classified into –

a. Herbiovorous

b. Phytophagus

c. Detritophagic

d. Carnivorous

e. Predatory

f. Omnivorous

g. Coprophagus

On basis of tropic level, fishes are grouped into-

Plankton or Filter Feeder – Catla & Silver Carp.

Column Feeder – Rohu.

Bottom Feeder – Nain.

Usually Herbivorous, Carnivorous show definite peak period in feeding, while omnivorous show little variation throughout the year.

2. pH – When pH of water drops below 5.5 metabolism lowers rapidly & apatite of fish is affected. This ultimately affects the ingestive variation (Food intake) of fish.

However the cultivable carp adapt themselves to weak alkaline water of pH 7 to 8.5.

3. Oxygen – The optimum range of pH for food intake is 6 to 7 ppm.

Factors influencing feeding

1. Temperature – Rate of feeding, metabolism and growth are affected not only by the ability of food but also by water temperature. IMC & exotic carps shows less food intake when water temperature falls below 150C and below 8 – 100C the fish specially Silver & Grass Carp almost stop feeding.

IMC have tolerance range of 17.5 to 380C, whereas Grass Carp have tolerance up to 400C.

The suitable temperature for Chinese Carps is 20 – 320C.

Fish seed transportation & Stocking

Fish seed collection from rivers

Techniques standardized for the riverine spawn collection nets in terms of their shape size and mesh-size to suit different hydrological conditions.

Why collection & transport of spawn

The spawn of the IMC is collected from flooded rivers during the monsoon months by means of shooting nets. The collection of spawn is highly localized. However farming of fish can be carried out almost anywhere in the most diverse habitats and climatic conditions- in ponds, lakes, reservoirs etc. This clearly indicates that there is a need to transport fish spawn or fry from its collection centre in the place of fish farming.

Fish seed transportation

The traditional practice of transporting fish seed in earthen pots (hundies) used to cause heavy mortalities. Techniques developed for packing and transport of spawn, fry and fingerlings in polythene bags with oxygen, it has enabled to minimize the mortality rate to the great extent.

Transport under oxygen

Traditionally, fish seed transportation was done in earthen hundies, half filled with river water, wherein about 10,000 to 15000 live spawn were kept for transportation (Approx. 30 ml). Gradually the earthen hundies were replaced by aluminium ones. These hundies were manually carried on slings. As the oxygen demand of live spawn is high, periodic splashing of water is done to aerate it for enriching supply of dissolved oxygen to the spawn. These methods are still practiced in eastern India and invariably result in 30-40% mortality of spawn over long distance transportation.

The method of packing live fish seed under oxygen for transportation developed. In this technique a plastic bag of about 300 guage is supported in a container, usually used Kerosene or vegetable oil tins, improvised to have a hinged cover with a latch and locking facility. The bag is filled up to one-third with ambient water, and according to the time required for transport, 50,000 to 1,00,000 spawn are packed in one tin. The bag is then emptied of air and by means of an oxygen cylinder, slow release of oxygen is done to bloat up the plastic bag to fill the tin. It is then firmly tied and the tin is trasported.

Improvisations in the packing (transport by rail/truck/air)

Instead of used tins, new GI sheet tins are used nowadays, which have a longer life specially for transport by rail/truck, etc. For trasportation by air, either tins are used or thermocoale sheet packing is done in corrugated cardboard boxes, which are light and hence, the freight expense are less. However, the oxygen-filled plastic bag for spawn is basically utilized in each case.

Such methods are also used for trasportation of fry and fingerlings produced in hatcheries. The number of seed packed per tin however, is different. About 1000-1200 fry (20-30mm) or 500 to 600 fingerlings (40-50mm) are packed per tin for a 24 hours journey.

Fish seed stocking in ponds

Carp spawn transported from hatchery is acclimatized in nursery pond and released during cool hours of the day, i.e. in the morning or evening. Acclimatization is an important aspect for spawn survival and needs attention to avoid any abrupt change in water quality, importantly temperature and pH.

Generally mono-species rearing of spawn is practiced in carp nursery. Stocking density of the spawn is determined based on the pond productivity & the type of management measures to be followed. The stocking density in earthen nurseries normally ranges between 3-5 million/ha. However it can be increased to 10 million/ha with better management measures. With proper pond management survival of 40-50% of fry is normally achieved in earthen nursery at the end of 15-20 days.

Fish seed stocking in ponds

In earthen rearing ponds, usually stocking density followed is 0.2-0.3 million fry/ha, which can be further increased in ponds with facilities for water circulation/exchange and/or aeration etc. within 2-3 months of rearing fry grows to fingerling of 80-100 mm in length, normally survival of 60-70% is achieved in rearing ponds with proper management.

In grow out culture ponds in low-input system stocking of carp fingerling up to 3000/ha

Generally a density of 5,000- 10,000 fingerlings/ha is kept as a standard stocking rate in carp polyculture for a production target of 3-5 tonnes/ha/year. In seasonal ponds or where water level becomes limiting during summers, it is reduced to 2,000-3,000 fingerlings/ha to obtain higher growth.

With provision of water exchange and aeration, higher target fish production level of 10-15 tonnes/ha/year are achieved by resorting to stocking ponds at a density of 15,000-25,000/ha.

Fish Food Organisms & their Production

Plankton – It is a collective term applied for very minute (microscopic) extremely diverse forms of organisms both plants and animals. That are floating at the will of wave and other water movements. The plankton occurs in all natural waters as well as in artificial impoundments like Ponds, Tanks, Reservoirs etc.

The term plankton was coined by Victor Hensen (1887). The single planktonic organism called Plankter.

The plankton community is comprised by organisms of plant origin – Phytoplankton, Animal origin – Zooplankton.

Phytoplankton – These are represented by all the classes of algae i.e. Chlorophyceae (Green algae), Cyanophyceae (Blue green algae), Bacillariophyceae (Diatoms), Euglenophyceae, Pyrophyceae.

Zooplankton – are represented mainly by 1. Protozoa 2. Rotifera 3. Crustacea

Majority of zooplankton population in inland water is comprised by Rotifera, Cladocera and CopepodaHowever in Certain water bodies Ostracode may also present in sizeable

proportion.

PhytoplanktonThe main group of phytoplankton are

Blue-green algaeCyanophyceae

Dinoflagellate Dinophyta EuglenoidsEuglenophyta

Golden algea ChrysophyceaeDiatoms

Bacillariophyceae Green algae Chlorophyta

Oscillatoria Ceratium Euglena

Uroglena Cymbella Pediastrum

ZooplanktonThere are 3 main groups of Zooplankton

1. Ciliata (Protozoas)

Paramecium Keratella

2. Rotatoria (Rotifera)

Daphnia

3. Crustacea

Eudiaptomus Nauplius

Classification of Plankton1. On the basis of size –

a. Macroplankton – Visible by naked eyes.b. Netplankton – Caught by bolting silk net no. 25 of mesh size 0.03 to 0.04 mmc. Nanoplankton – Smaller than netplankton.

2. On the basis of distribution a. Limmnoplankton – Found in lake b. Heleoplankton – Found in pondc. Rheoplankton / Potamoplankton – Found in running waterd. Halioplankton – Found in salt watere. Hypalmyroplankton – Found in brakishwater

3. On the basis of Origin – a. Autogenic plankton – Plankton produced locallyb. Allogenic plankton – Introduced from other locality

4. On the basis of contenta. Euplankton – True planktonb. Psedoplankton – Debris

5. Life historya. Haloplankton – Free floating throughout lifeb. Meroplankton – A part of their life is free floating

Plankton community undergo mark seasonal fluctuations in various types of Inland water bodies. Population density of plankton is an indicative of productivity of water bodies. High population of both phyto and zoo plankton are observed in nutrient rich ecosystem. A mean phytoplankton biomass of 10mg/m3 in euphotic zone is indicative of high eutrophic condition.

The population of zooplankton is also largely depend on phytoplankton population, majority of rotifers, Cladocera and population of Copepods is dependent on phytoplankton for food. Besides phytplankton, zooplankton also invariably utilize detritus organic particles.

Rotifers being small in size, as compared to Cladocera & Copepoda serve as food for the fry, in the early stages.

The Population of phytoplankton is mainly dependent concentration of nutrients specially nitrogen & phosphorus. Under very high nutrient condition, phytoplankton often form bloom. Most common bloom forming species areEuglena, Chlorella, Chlamydomonas, Microcystis, Anabaena, Oscillatoria

Excessive population of phytoplankton are often main cause of organic pollution. The plankton population is also dependent on temperature, rate of grazing and predation.

Plankton constitute the most important part of food chain in aquatic ecosystem most of energy in grazing food chain is transferred to Plankton.

Under culture condition, the fertilization of pond is routinely to raise population of plankton so as to provide more amount of natural food.

In the intensive culture and rearing of spawn, the natural food in the nursery soon gets exhausted. To compensate for this depletion, the desired species of Rotifers are cultured separately and introduced into the nursery pond.

Culture of fish food organisms

Culture of fish food organismsThe earlier stages of shell & finfish are known to feed protein rich zooplankton such as Brachionus plicatilis, B. rubens, Euchlams spp. Daphnia carinata, Moina spp. Ceridaphnia spp. Artemia salina (Brine shrimp)

Culture of DiatomsNavicula, Chlorella, Cyclotella spp. It can be undertaken in simple test tube to large outdoor tanks. Monoculture of Diatoms spp. Serve as an ideal food source for zooplankton culture and also for fish larvae in indoors & outdoors.

1. Sterilization of glasswares – Cotton plugs, glasswares such as Petridish of 5-10 cm diameter, test tubes and flasks of 1-2 L capacity etc. are first cleaned with chromic acid or chlorate sulphuric acid followed by repeated rinsing in distilled water & sterilization in autoclave under a pressure of 7kg/cm2 for 30 min.

2. Preparation of medium – The culture medium is prepared with various salts and is sterilized in an autoclave, cooled & kept ready.

3. Culture in test tube or Petridish – In each of sterilized test tube a known quantity of the above medium in introduced aseptically & the tube is cotton plugged. Similarly a pair of suitable Petridishes, one fitting over other is taken & in the lower dish a known quantity of medium is introduced aseptically and covered immediately with other Petridish. The live diatom shells are sorted out from planktons sample obtained by the filtration of pond water with a plankton net, with the help of a binocular microscope & pipette. These cells are identified & washed repeatedly in the sterilized nutrient medium in 5-6 watch glasses. The cells after repeated washing, transferred to test tube or Petridish containing medium.

The culture should be exposed to light from a fluorescent tube. The sub-cultures are made periodically & the cultures of test tube are then transferred to flasks (1-3L) capacity, containing the nutrient enriched medium.

Before inoculating the flask with test tube cultures, it is necessary to record the number of cells/ml and volume of cultures. Further when the cells are in exponential phase of growth. The cultures should be harvested & transferred to larger culture tanks.

Rotifer culture Controlled culture Simple culture bottles

Test tube & Petri dish

4. Batch culture - This involves mass culture of diatoms in outdoor circular tanks having 500 L capacity. The bottom of these tanks slopes to a central outlet for empty.

The outdoor tanks containing filtered freshwater, filled with fertilizer- mixed in the composition of Ammonium sulphate (100g/m3), super phosphate (15g/m3), & Urea (5g/m3).

The prepared cultures are transferred to these outdoor tanks & are maintained for 1-2 days. It would be better if the tanks are placed in areas without direct sunlight.

Mass culture of ZooplanktonIt includes culture of Rotifers and Cladocerans. It is undertaken in circular tanks of 5000 L capacity, & kept in areas with artificial light or diffused sunlight and covered with polythene sheets.

Before use, the tanks are steam cleaned & filled with about 1000 L of Diatom culture, where the number of cells would be about 106 cells/ml. The tank is then inoculated with Rotifers & Cladocerans, collected either from the cultures already maintained or from the natural sources at the rate of 10 individuals/ml.

The Rotifers or Cladocerns are harvested with a net of fine bolting silk, when they attain density of 100 organisms/ml. This requires about a week. These are then transferred to fish & shellfish larval rearing tanks or frozen for future use.

Cladocerans culture

Hatching of Artemia cyst

Culture of ArtemiaArtemia is commonly known as Sea monkey or Brine shrimp. Inhibits in Salt Pan Waters (>200ppt salinity). The eggs/ Cyst are of commercial importance as the hatched Nauplii, serve as an ideal protein rich food source to many fish & Prawn Larvae in culture system.

In laboratory, Artemia cyst allowed to float on the surface of filtered normal sea water, where they hatch in 24-48 hours depending upon the atmospheric temperature. Eggs can also be incubated in a solution containing two full spoons of common salt mixed in 1 L of freshwater.

Hatching of Artemia cyst – about 250g cysts are sprinkled in 100 L of seawater (30-35ppt salinity). Vigorous aeration & suitable temp (26-300C) may fasten hatching process. The hatched Nauplii could be attracted using a light source & collected by a very fine meshed net. They are either transferred to culture chambers containing fish or prawn larvae as live food or can be stored frozen as Rotifers and Daphnia.

Algal cultureAquaculture animals have to obtain all their nutritional

requirements through food which they consumed. In Nature, most of them subsist on live foods consisting of plants and animals obtained from the environment. The initial source of food for many larval organisms is phytoplankton. This is associated with the size of the larvae at hatching. After a certain period of time the larvae of most species can be fed mostly on zooplankton or a combination of plant and animal matter. It is possible to obtain both types of food from nature. But is will be more convenient to culture algae under controlled condition for hatchery use.

An algal culture system generally consists of 3-4 main stages, starting with and maintaining stock culture from which cultures are made at regular intervals, in small flasks (50 ml volume), followed by culturing carboys (12 L) or tanks (300 L).

Stock cultures can be maintained in small screw top test tubes (that can be autoclaved for sterilization) using low level enriching media for maintenance rather than heavy growth.

Algal cultureA 12 hours photoperiod is considered enough for Diatoms. The

incident light level requires for stock culture is 750-1000 Lux. Which can be provided by two 30-40 watt cool white fluorescent bulbs placed in front of stock culture tubes. A temperature of about 240C is maintained, after about a month the stock culture should be transferred in aseptic condition, to create new culture lines.

In 2nd culture phase – Aliquot (of 2ml) of stock culture are used to inoculate autoclaved small flask (125 ml). The light intensity about 1500 Lux is necessary though aeration may not be necessary. The flask should be shaken to reduce shading. A four days old flask culture is used as inoculum for the next phase of culture.

The next phase of culture in Carboys (12-20 L capacity) with an autoclavable stopper fitted with an air supply line & a screw top inoculation tube. The latter enables more or less aseptic inoculation of cultures & the aeration pipe reduces settling of cells on the bottom.

Algal cultureAfter 4 days of growth, in carboys the final phase of culture can be started.

For this larger fibre glass tanks are used. While for laboratory use 300 L tanks may be suitable. For commercial farms, larger tanks of about 1 ton capacity will be necessary. Circular or rectangular tanks painted white are often preferred, illumination is provided by a series of 40 watt fluorescent bulbs suspended directly above the tanks. Constant illumination & aeration with air stones or other devices for adequate circulation are necessary.

Several methods are available for harvesting algae, high density cultures can be concentrated by centrifugation. Harvesting is done by siphoning off the supernatant or by skimming cells of surface as applicable. Centrifugation of algal cultures can be performed with standard dairy cream separator. The rate of flow of culture from the bowl to the centrifuge head is adjusted according to species of algae & centrifugation rate of separator. The algae deposit on wall of centrifuge head has to be removed and suspended in water where possible live algae are directly pumped into larval tanks. When necessary concentrated cultures are frozen for storage.

Aquatic insects and their controlAquatic insects constituted about 4% of total insect fauna, which exist in the

world. Aquatic insects either in their adult or larval stage prey directly on carp spawn or injured the young ones by sucking body fluid or indirectly competing for food with carp spawn. Therefore, the pond culture technique includes the control & removal of harmful aquatic insects. Such eradication of harmful insects from ponds play a very important role in increasing fry survival rate.

However, common insects found in the culturable ponds being smaller in sizes, can not make any harm to rather bigger sized fish including fingerlings & yearlings. Thus removal or control of insects in stocking pond is not compulsory. Out of 11 orders of Class Insecta - 3 orders 1) Hemiptera 2) Coleoptera 3) Odonata are relatively common in freshwater ponds.

The important families with examples under different orders are - Family Example

1. Notonectidae a. Notonecta (water boatman or backswimmers)b. Anisopes

2. Belostomidae a) Belastoma (Giant water bug)3. Nepidae a) Nepa (Water scorpion)

b) Ranatra (Water stick insect)

Water ScorpionGiant water Bug

Water Scavenger Beetle

Water Boatman

Backswimmers

Order - ColeopteraThe important families with examples under different orders are -

Family Example1. Dytiscidae a. Cybister (Diving beetle)2. Hydrophilidae a) Hydrophilus (Scavenger beetle)

b) Sternolophus (Water scavenger)3. Gyrinidae a) Gyrinus

b) Dineutes (Whirling beetles)

Order – Odonata Dragon fly nymph

Order – Hemiptera Includes water bugs, are relatively more dangerous as their complete aquatic life both larval as well as adult stage. They have very strong piercing type mandibles.

Intensity of predation- Cybister consumes about 15-20 fry of 20-40 mm in 24 hours.- Anisopes & Ranatra consumes 182 and 122 carp spawn respectively in 24 hours.- Dragon fly nymph consumes about 7 fry in 3 hours & 24 spawn in 24 hours.- These bugs secrete toxic salivary substances which kill the prey.- Sternolophus & Gyrinus suck body fluid and even sometime kill spawn and fry.

Control measures Simple way of controlling is by netting but complete removal is not possible by netting. Application of Oil Soap emulsion in ratio of (56:18)/ha (56 L oil & 18 Kg Soap per ha) is an age old practice. It is recommended to apply 12-24 hours before releasing the spawn. The oil film float over the surface of water.

Mode of action of soap-oil emulsionThese insects periodically come to surface regularly for breathing atmospheric oxygen by raising their tracheal tubes over water surface. Oil films enter into tracheal tube and damages respiratory system of insects by blocking.

Method of applicationSoap & oil are heated and mixed into homogenous solution and then it is sprinkled over water surface manually. Addition of soap or any detergents helps to form thin film with micro droplets at the surface.

1. Kerosene oil – 80 – 100 L/ha2. Diesel – 1000 ml in 200 m2 area3. Turpentine oil @ 75 L/ha used to kill most of the insects in 30 min.4. Buton @ 1 - 2 ml / L for 25 m2

Sampling and harvesting

Periodical sampling is performed to know the length weight, growth rate, feed utilization, and also to avoid disease outbreak in pond through taking preventive measures which are ensured by proper management of the soil-and-water quality, following proper feeding schedule, use of balance feed, periodic sampling for health check, and minimising outside influence on the pond.

Sampling by cast net

Harvesting of fryIt is done during cool hours preferably at morning or evening. The fry harvested are usually

kept in crowded condition under shower for 2-3 hours in hapa fixed in same nursery-pond. This facilitates their release of faecal matters, minimising faecal load during transportation.

Harvesting of fingerlings Within 2-3 months of rearing, fry grows to fingerling of 80-100 mm in length. Fingerlings are

effectively harvested by using drag-net of suitable mesh size. Morning hours with low temperature is the most preferred time for harvesting. Normally survival of 60-70% is achieved in rearing ponds with proper management. Fingerlings can be further reared in rearing pond to obtain bigger juveniles. However, in such a case, the population has to be thinned out. One of the recent concepts followed in fingerling rearing is to raise seed at higher stocking density round the year with low rate of feeding so as to obtain stunted seed. This method ensures round the year availability of fingerlings for stocking in grow-out ponds. Further grow-out pond stocked with stunted fingerlings are reported to give better survival rate; higher feed utilization efficiency and higher production than those stocked with normal ones. Stocking with stunted fingerlings has been increasingly in practice in Andhra Pradesh (Kolleru lake region) where fingelings grown to juveniles of 150-250 g size in separate adjacent ponds are stocked in grow-out culture ponds.

Harvesting of grow-out pondGenerally carps are harvested after a grow-out period of one year during

which it reaches marketable size of 0.8 - 1 kg. However, these carps are even marketed in smaller sizes of over 300g except that of silver carp; the marketable size for which is over 1 kg. In multi-harvesting system, the fishes attaining market size are periodically harvested from the pond, releasing back the smaller ones for further growth. While intermittent harvesting are done by drag net of suitable mesh size, final harvesting is done by complete draining of pond.

Based on the production cycle, the carp culture can be of single stocking – multiple harvest and multi stocking-multi harvest or rotational type culture. Single stocking- single harvest method of culture is usually done for 6 months to 1 year. Such method is followed in traditional & semi-intensive practices. Semi-intensive method also makes use of single stocking-multiple harvest method where comparatively higher stocking density maintained than that of single stocking-single harvest. As fish biomass in the pond increases, larger fishes are partially harvested at monthly intervals. In multi stocking-multi harvest, marketable size fishes are harvested from pond at regular intervals with periodical restocking.

Harvesting fish from ponds with an internal harvesting sump

Cull-harvesting fish several times before drain harvesting increases the yield of market-sized fish

Market sized fish can be kept alive while harvesting continues

Sorting while seine harvesting

Cull-harvesting or sampling is an opportunity Size grading of fish performed to get higher returns

Harvesting fish using a brailer

Harvesting salmon from net cages

Harvesting & marketing

Carps produced from culture ponds are mostly sold in local market, either in live or dead condition. The Indian major carps are also transported to adjacent deficit areas as well as to distant places, even 2000 - 3000 km away from the production site, in insulated vans with ice. Fresh fish fetches about one-and-half-times higher market price than iced ones. The price in the domestic market is influenced by demand and supply.

If you are not marketing your fish alive, you should kill-chill them in a bath of iced water immediately after harvesting to get

the best quality

The last few fish may have to be caught by hand, especially when the pond does

not drain well

Bird predation causes problems during drain harvesting

Supplementary feeding survival & growthThe natural productivity of pond, irrespective of the level of its

augmentation through fertilization, is not capable to sustain a higher level of fish biomass in semi-intensive grow-out. Due to the limitation in availability of natural food in pond at higher stocking density, the energy requirement for somatic growth can be met only through provision of supplementary feed. Mixture of ground nut/mustard oil cake and rice bran at 1:1 has been commonly used in carp culture. Vitamin & mineral requirements of fish are normally met through intake of natural food ( at least 50% of the diet) by carps.

With shift towards intensive fish culture, recent years, formulations of balanced feed have received considerable attention. Several balanced feed formulations have been developed making up deficient essential amino acids, fatty acids and incorporating vitamins and minerals. All these ingredients are blended together at required proportion for preparation of carp feed. The commercial production of supplementary feed is usually in pellets of different diameter, to provide higher water stability, consumption and utilization by the fish.

Supplementary feeding survival & growth

Underfeeding depresses fish growth while overfeeding results in wastage of food, leading to deterioration of water quality. As feed cost constitute more than 60% of the recurring expenditure in carp culture, feed management, is an important aspect for ensuring optimum growth of carps and limiting production cost, besides maintenance of pond aesthetic condition. The recommended practice is to provide feed at 3-5% of body weight of stocking material initially and subsequently at sliding scale from 3 to 1 %

In grow-out ponds, survival level usually reduces to around 80% during initial 2 months of culture, beyond which survival remains almost constant in properly managed ponds. Therefore, survival percentage of 70-80% is considered for estimation of biomass. The daily ration is adjusted according to the biomass estimated from monthly sampling. The daily ration is provided in pond preferably in two splits during morning and evening in feeding trays or perforated gunny bags suspended at regular intervals in pond. Grass carps are provided with aquatic vegetations at periodical intervals.

Grass carp

Common carp

Bighead carp

Silver carp

Aquaculture of carpAquaculture of carp

It may be defined as the association of two or more normally separate farming systems which become part of the whole farming system. The major features of this system include:• Recycling of waste or by-product in which the waste of one system becomes the input of other system.• Efficient utilisation of farm space for multiple production.Integrated livestock-fish, poultry-fish, and rice-fish farming and crop rotation in fish ponds have been well developed and practised in countries like China, Hungary, Germany and Malaysia. Indian freshwater aquaculture has been largely organic-based, with inputs derived from activities of agriculture and animal husbandry with plants and animal residues forming the major component of feeds and fertilizers in carp polyculture. India being an agrarian economy, produces large quantities of plant and animal residues. Activities like mushroom cultivation and rabbitry, silviculture, apiculture, etc. apart from providing for diversification of farming systems, also provide huge quantities of organic material, that may become resources in the aquaculture system. The agro-based industries like distilleries and food processing pants also produce the effluent that could be recycled to aquaculture apart from the well known resource-domestic sewage.

INTEGRATED FISH FARMING

Fish-duck culture Cattle on pond dyke Poultry shed on fish pond Pig site on dyke

INTEGRATED FISH FARMING

INTEGRATION OF FISH WITH AGRICULTURE, HORTICULTURE AND ANIMAL HUSBANDRY

Paddy cum fish culture Fish cum horticulture

Integrated fish farming system works in following way:• Trapping of solar energy and production of organic matter by primary producers.• Utilization of primary producers by phagotrophs or tertiary consumers.• Decomposition of primary producers and phagotrophs by saprotrophs or osmotrophs.

ECOSYSTEM OF INTEGRATED FISH FARMING

• Release of nutrients for producers.

The animal waste in water body enter into the food chain in three different ways• FeedCertain bottom feeders like Cyprinus carpio and Cirrhinus mrigala directly utilized the organic particles which are generally coated with bacteria along with other material.• Autotrophic productionSome of the decomposed portion of waste products provides nutrients for the micro-flora (autotrophs), while non-mineralised portion provides food base for bacteria and protozoa (heterotrophs). Temperature, light, micro and macroflora, inorganic nutrients, carbon, phosphorous and nitrogen are the basic inputs required for photosynthesis process.• Heterotrophic productionMicro fauna (zooplankton) feed on small manure particles coated with bacteria. In the process, bacteria is digested while rest is excreted. In this heterotrophic production system micro fauna (protozoans and zooplanktons) are produced finally shortening food chain. This system of production is not linked with the process of photosynthesis.

Integrated fish farming systems utilise the waste of live stock, poultry and agriculture byproducts for fish production. About 40-50 kg of organic manure can produce 1 kg of fish. Fish farms having an integration with mulberry cultivation, sericulture and silk extraction from cocoons allow the pupae to be utilised fish feed and the worm faeces and wastewater from the processing factory to be used as pond fertilisers. Pond silt can be used as fertiliser for fodder crops which in turn can be used to raise live-stock and poultry or as fish feed. Thus a recycling of waste is done in integrated fish farming system.

The scope of integration in a fish farm is considerably wide. Ducks and geese may be raised on the pond, pond dykes may be used for fruit plants and mulberry cultivation or for raising pigs, cattle, and dyke slopes for fodder production. From integrated fish farming systems not only fish but meat, milk, eggs, fruits, vegetables, mushrooms etc. can be obtained. This system fully utilizes the water body, the water surface, the land, and the pond silt to increase food production for human consumption.

Advantages of integrated fish farming systems

Fish culture can be used in conjunction with rice cultivation to increase productivity. Rice fields form the natural habitat for a larger variety of indigenous species of fish which gain entry only from the nearby perennial water bodies. The fishes feed and grow on natural food available and the farmers usually collect the fish during rice growing season and/or when the water level subsides. In eastern India, rice cultivation varies due to impaired drainage.

1. RICE - FISH SYSTEM

Field design of rice-fish plotsThe rice fields which retain water for a fairly long duration and free from flooding are generally suitable for rice-fish integration. Some modification of rice-fish plot is required to make the system more profitable. Clay soil is suitable. A peripheral, trench is excavated around the rice growing area (width 3.5 - 4.0 m, depth 1.5 m) which is blocked at one place and connected to the main land for easy access for farmers and agricultural appliances to the rice plot. The rice plot may range from one acre to one hectare or more and preferably be rectangular or even square. A dyke is constructed all around.For a 1 ha plot area required for dykes, trenches, pond refuge and field will be:

Dykes 2000 sq. m. (20%)Trenches and pond refuge 1300 sq. m. (13%)Field 6700 sq. m. (67%)Modifications in size may be made as per availability of available land.

Culture methodsImproved varieties of rice like Panidha, Tulasi, CR 260-77 are cultivated in season which have tolerance to submergence and pest attacks. Fertilization schedule includes 40 kg N. and 20 to 30 kg each of P2O5 and K2O/ha at the time of seeding, besides FYM at 5 to 10 t/ha.

Fish and PrawnCatla, rohu, mrigal and common carp in combination with freshwater giant prawn are stocked in equal proportions @ 10,000 individual/ha. These are fed with rice bran and mustard groundnut oil cake @ 2-3% of the total body weight. Manuring schedule includes application of cow manure at 10 t/ha/yr, while liming is done @ 200 to 500 kg/ha. These are harvested periodically along with receding water levels.

1. RICE - FISH SYSTEM

1. RICE - FISH SYSTEM

Horticulture on the dykesAfter the harvest of rice certain crops which require lesser amount of water like water melon, groundnut, vegetables, cow pea, money etc. can be grown. Top of the bund which is 10% of the pond area is utilised for growing vegetables and fruit bearing plants.

Rice-fish system results in 168% intensity of cropping in field and 400% on bunds as compared to 52% in the case of traditional monocropping of rice. Rice-fish system provides a net annual income of around Rs. 30,000/ha in the first year which accounts for about twelve folds income over farmer’s traditional practices and three folds over the improved monocropped rice.

This system encourages synergism between rice and fish leading to increase in grain yield by 5-15% and straw yield by 5-9%. It facilitates crop diversification, thereby reducing investment risk. It promotes gainful linkage between rice, fish, prawn, vegetables, fruit crops and other resulting in better resource utilization as well as conservation of the ecosystem. It generates year-round employment in the farm.

Aquaculture practices

On the basis of management intensity, fish culture can be classified into: 1. Extensive culture - Selected species is stocked into properly

prepared pond. Use of fertilizers and supplementary feed is in limited extent. Production is very low.

2.Semi-intenstive culture - Stocking is done in moderate density. Formulated compound feed is provided as per nutritional requirement from external sources.

3. Intensive culture - Stocking is done with hatchery reared seed in high density. Water quality is maintained by frequent exchange together with constant aeration. Food requirement is met fully with formulated feed. Production is high.

4.Super-intensive-High stocking density with total water exchange through biological filter. Constant water quality monitoring, aeration and encapsulated pelleted diet is provided. Feeding and stocking manipulation is done. Production is very high.

Different Aquaculture Practices1. Monosex culture - Separate sex of individual species are cultured, Ex-Tilapia2. Air-breathing fish culture - Derelict shallow water bodies with poor oxygen

content are utilized for culturing air breathing fishes like Singhi, Mangur, Murrels (Channa spp.).

3. Predatory-Prey culture - Can be undertaken in shallow and swampy area. In which carnivorous fish like murrels are cultured along with their prey fish Tilapia.

4. Raceways - In running water systems like streams, series of rectangular, circular earthen or cemented tanks are constructed for fish culture.

5. Sewage fed fish culture - In this, sewage water is treated in oxidation ponds and subsequent water used for fish culture.

6. Circulatory system culture -This system can be placed in areas of water scarcity. Fishes are cultured in ponds/tanks where water is re-circulated through biological filter, and other filter and finally disinfected.

7. Ornamental fish culture - Coloured fish such as Gold fish - Xiphophorus auratus, Guppy fish - Lebistes reticulatus, Molly - Molliensia latipinna are cultured in aquarium or pond.

Different Aquaculture Practices

8. Culture of fish food organisms - Mass culture of protein rich live fish food - Cladocerans, Rotifers, Tubifex, Insects have been found essential for larval stages of fin and shell fish.

9. Sport fish culture - In this cold water species are cultured in upland water. Examples - Trout and Mahseer.

10. Integrated fish farming - It is multi community fish farming in which fish are cultured with agricultural crops, live stocks, and Poultry. This is AAA system - Agriculture Crops, Animal Husbandry and Aquaculture.

Culture of fish in Raceways, Cages & EnclosuresRaceways - Raceways are designed to provide a flow through system to rare

much denser population of animals. Abundant flow of good quality well oxygenated water is essential to provide respiratory requirements and to flush out metabolic waste particularly ammonia.

Raceways are comparatively small in size and occupy much lesser space than ponds. They are made up of reinforced concrete of cemented ponds. Earthen raceways can be coated with plastic material to reduce loss of water through seepage. The main source of water is streams and deep well boring.

In designing a raceway a slope of 1 to 2 % is preferred for water flowing from one end to another end. It is generally advisable to have water supply reserve for emergency. A storage reservoir near the beginning of raceways system from where water can flow into raceway by gravity would be most useful. It is important to have water control structure to regulate the flow and depth of water discharge from the bottom of raceways and include screen to prevent loss of stock. Removal of water from bottom helps in flushing of metabolic waste and increase oxygen content. It is essential to adjust the rate at which water is pumped into raceway in order to prevent overflow or emptying for cleaning raceway bottom. In emergency, a suitable suction device can be used.

Limitations

Such closed systems has certain limitations because of 1. More demand of energy and power for water flow.2. The production is dependent on water flow.3. Species of fish such as Carps, Trout, Catfishes, Tilapia, Eels

and Seabass are taken.

These systems are also used for rearing fingerlings.

CagesThe cage culture was first started in Cambodia from where such practices transfer

to Thailand then to Indonesia, Vietnam and Japan. The significance of cage culture become more relevant for those countries where suitable water supply and land for fish culture are becoming less available.

Types of Cages : There is no fixed design or the size of cage for culture. They are made of galvanized welded wires and nylon meshes in USA, Japan etc.

In India – the cages is made of split bamboo and are of various size ranging from few square meters to 15 sq. meter. For Carp culture a Cage is 2 meter deep and for marine fishes it is 3-5 m deep. The shape is generally rectangular and the cage may be stationary fixed to some strong poles. For free floating, steel drums or empty barrels or synthetic floats are used. The size of mesh is small in Cages in which fry are cultured. These are called as Rearing Cages. However, as fry grows to fingerling they are transferred to Stocking cages, which have large sized mesh (4 cm) to allow free circulation of water through cages. The no. of fingerlings to be stocked depends upon size, depth, surface area of cage and the species of fish to be cultured.

Fish Species cultured in Cages

There are about 50 species of marine and freshwater species to be cultured. The species which are generally cultured in cage in various country are – Common Carp, Tilapia, Pungasius, Clarias spp., Channa spp., Trout, Anabas, Notopterus etc.

Stocking DensityDepends on carrying capacity of the water (water spread area and quality), water exchange, species of fish & quantity. The stocking rate for rearing Spawn to fry – 10,000 /m2

Fry to fingerling – 2800 /m2

Fingerling to advanced fingerling – 300/m2

However, it is believed that fish stocking at initial stage should occupy 45% of cage volume so that fish can have normal growth. The artificial feed eating fishes occupy 85-90% of total stocking density & natural food eaters occupy 10-15% in cage culture.

Pen & EnclosuresThe most effective and suitable type of enclosure used for aquaculture is one

formed by damming a bay, estuary or rivers. Sites are selected where barriers can be constructed across narrow section or channels in order to reduce cost and easy operation. There may be two or two series of barrier – one up-stream and one down stream. The dams are constructed with stones, earth or concrete. They hold screens to allow free flow of water.

Pen culture was taken on commercial scale in Leguna de Bay and San pablo Bay, lake Philippines from 1968. For rearing Milkfish.

Presently, commercial pen culture of fish is being done in Philippines, Indonesia, China etc. the species are Milkfish, Grass carp, Big head, Silver carp, Tilapia etc.

Modern Pens are constructed by Nylon or Polythene mesh nets instead of traditional split Bamboo. The nets are attached to fixed post set at every few meters and the bottom of net is buried in substrate.

Limitation of Enclosures – Strong water current, turbulence, wind and wave action are not congenial.

Cage culture

Fish Pen at Bay

Air-breathing fish cultureCulture systems of air-breathing fishes such as murrels (Channa spp.),

magur (Clarias batrachus.), singhi (Heteropneustes fossilis) and koi (Anabas) in open ponds and cage culture of singhi and murrels have been developed. Air-breathing fishes, owing to their unique taste, are considered a delicacy for fish consumers, but production of different indigenous air breathing fishes through aquaculture has been unexplored in India. These fishes grow in shallow ponds and tolerate higher water temperature and thereby sturdy to withstand dry summer spell.

Existing shallow, d e r e l i c t , seasonal, stagnant ponds could be e f f e c t i v e l y u t i l i s e d for a sizeable production of air-breathing f i s h e s with low input, as could be the specially constructed ponds i n the proximity of irrigation canals with flowing water, or tube-wells for production of as much as 80 tons of Clarias and Heteropneustes /ha/6months with intensive operations. Air-breathing f i s h culture in p a r t i c u l a r is oriented t o shallow water environment and is essentially a low input, high yield technique; the production is commensurate with the intensity of management. There is no requirement for f e r t i l i z e r s or manure. The only material inputs are the fingerlings and the feed, and in case of intensive operation, the water management is an essential input.

Well known as mangur and is the most preferred indigenous catfish and is hardy in nature. It is an annual breeder, which spawns during mansoon in large water logged areas with accumulation of rainwater. In nature, it shows parental care. Female scoops nest and fertilized eggs are deposited in the nest. Such natural simulations are made for natural breeding of Clarias spp. in South-East Asian countries for getting stocking material.

Maintenance of healthy brood fish is a prerequisite for successful seed production in captivity. Usually, this species attains maturity in one year with 100-150 g in weight and can be employed for breeding. Mangur usually breeds in mansoon during June-August. The fishes are taken out of brood stock ponds and kept separately in plastic containers breeding operation. Males and females can be distinguished by the secondary sexual characters. The abdomen of a gravid female is round and bulging with a reddish colour vent having round and button-shaped genital papilla, and the males have elongated and pointed papilla. They are either bred through hormonal administration or through environmental manipulation.

Clarias batrachus (Mangur)

Clarias batrachus induced breeding

Females are induced bred through commercially available synthetic hormones, i.e. Ovaprim/Ovatide/WOVA-FH @ 1.0-1.5 ml/kg body weight or carp pituitary extract at 30mg/kg of body weight. The stripped eggs are fertilized artificially with sperm suspension. However males do not require hormonal injection. Unlike carps males of this species do not ooze sperm on its own, and thus they are cut open at abdomen, testes are removed and macerated keeping it in normal saline solution (0.9% sodium chloride) to get sperm suspension which could be used within 24 hour at room temperature.

Females are stripped after a latency period of 15-17 hours and eggs are fertilized with sperm suspension. The fertilized eggs are then washed thoroughly and transferred to flow-through hatchery. The eggs of this species are adhesive in nature, and light brown eggs are considered good while white are unfertilized. Ideal temperature for hatching is between 170C and 300C, and hatching takes place between 24-26 hr.

SEED PRODUCTION AND GROWOUT OF MAGUR

Air-breathing fish cultureAquatic weed control

The earthen ponds/stone pitched ponds/cemented tanks are suitable for grow-out culture of mangur. Generally, high density of 50,000 – 70,000/ha is recommended for culture of this fish. Bigger size seeds (5-10g) show good survival and growth during culture. The fishes are fed at 3-5 % of body weight with pelleted feed in feeding basket placed in different places on the pond.

Since the fish is an air-breather, they normally come up to water surface for gulping atmospheric-oxygen. This kind of habit attracts birds for predation. Therefore, it is required to cover ponds with net to protect catfishes. The fishes attain a marketable size of 100-120 g during culture period of 7-8 months. Harvesting is done by complete dewatering and picking them manually from culture ponds. Production to the tune of 3-4 tonnes can be achieved from 1 ha of water-area.

Clarias batrachus culture

Air-breathing fishes in nature are known to be carnivorous. But Clarias and Heteropneustes subsist on organic detritus when stocked in a heavily silted swamp. However, in culture operations the species responded excellently to supplementary feed consisting of dried marine trash fish, oil-cake, rice bran, compost and manure in various combinations and proportions. With dried marine trash fish and rice bran in the ratio of 2 : 1 for the first three months, and in the ratio of 2 : 3 during the remaining period of 5 months, the culture period indicated a conversion ratio of 1.5 : 1 for Clarias.

The addition of biogas slurry helps in reducing the trash fish component in the feed, thus economising culture operations. In nature, the Clarias attains a weight of 80-90 g in one year; whereas in culture operations with intensive feeding the fish can attain over 250 g in a 6-months growing period. Feeding of Heteropneustes under culture could be only rice bran and biogas slurry under semi-intensive culture whereas, fish meal could be advantageously incorporated under intensive operation. Murrels, however, have to be fed with dried trash fish or dried silk worm pupae.

Food, feeding & growth of air-breathing fishes

Sewage is the liquid waste discharged from domestic and industrial sources within an area. It is reutilized for culture of fishes like rohu, mrigal and catla.

Fig. Fish pond utilising sewage.

Sewage & waste

waste stabilisation pond

effluent

Fish pond

To irrigation

Water dilutionOver flow

City sewage is extensively used for fish culture. Before sewage is let in to a pond, it is diluted with the fresh water so as to maintain the dissolved oxygen content and reduce other toxic substances

Sewage-fed fish culture

Fig. Fish pond utilising sewage

Sewage-fed fish cultureThe wastes, including sewage and waste water produced by the

human community hold high potential for fish production. In India itself there are about 150 sewage-fed fish farms covering an area of about 12 000 ha. Very high production in the order of 7–10 tonnes/ha/yr has been obtained from ponds fed with sewage which invariably contains high percentage of N,P,Ca,K etc. An average production of about 7 t/ha/yr is easily obtained using a mix culture of 5 carp species (Ghosh et al., 1985).

The sewage fed ponds are generally dewatered completely during summer so as to remove all the carnivorous fishes. The pond is initially fertilized by introducing partially treated sewage effluent upto about 75–80 cm and then clean water is pumped in to raise the pond water level to 1.5 m. Within a month the pond stabilises with respect to dissolved oxygen and becomes suitable for stocking with fish seed. During raising of marketable size fish, additional fertilization with sewage effluent is carried out in small doses every month and the pond is netted frequently to help oxygenate the water and in course of netting the marketable size fish are also harvested.

REUSE OPTION OF WASTEWATER

• Wastewater Reuse for Aquaculture is long practiced technique. Nutrients present in waste water act as fertilizers to produce natural food such as plankton. Also a source of nourishment for the aquatic species for direct water consumption.

• Series of ponds can be manually constructed for the treatment purpose. Channels of treated effluent are the source of water supply for the fish ponds.

• Raw wastewater can be used for aquaculture, serving as a source of income as well as food for personal consumption.

Assessment of Positive & Negative Aspects

Positive aspects• Reliable source of income generation from market of fish consumers.• High nutrient content reduces cost on fish food.• Increases fish yield.• Meets food demand of fish growers as well.• Serves as a low cost sanitary disposal method of wastewater.• Provides ancillary job opportunity

WASTEWATER REUSE FOR AQUACULTURE

Negative Aspects

• Health risk with bioaccumulation of toxic chemical in untreated wastewater• High Nutrient loading in wastewater increases growth of Phytoplankton's & Algae that in turn decline in fish population• High Concentration of Ammonia increases fish mortality rate• Waste water provides excellent breeding place for mosquitoes and disease causing vectors• Health impacts finally translate into economic impacts

Induced breeding

Composite Fish culture

Integrated fish

farming

Pig cum fish culturePig cum fish culture

Paddy cum fish culturePaddy cum fish culture