METHODS & STRATEGY OF IMC FISH SEED PRODUCTION IN INDIA
Post no-1416 Dt 25/12/2019
Compiled & shared by-DR RAJESH KUMAR SINGH ,JAMSHEDPUR,JHARKHAND, INDIA, 9431309542,rajeshsinghvet@gmail.com
Availability of required quantity of seed of the desired species at the appropriate time is one of the prime factors that lead to success of aquaculture operation. Though remarkable success has been achieved over the years in spawning the carps, availability of seed of desired size still remains a constraint.
Fish seed production includes egg to spawn production for 3 days, spawn to fry nursing for 15-20 days, fry to fingerling rearing for 60-90 days and fingerling to yearling rearing for 8-9 months. Thus the carp seed may be categorised at its final size into spawn (6-8 mm size), fry (20-25 mm size), fingerlings (100-150 mm size) and yearlings (100-200 g weight).
Spawn production in rural area
Common spawn production
In rural areas generally carp spawn are generally produced twice during June-August and January-March of the year, following the adaptive breeding methods.
Pond breeding:
Common carp brood fish are reared in composite fish culture ponds. In season, clean aquatic weeds such as Hydrilla / Najaj or water hyacinth are placed in pond’s corners or inside floating bamboo frames in the evening hours. During late night to early morning fish breed naturally and eggs are attached to aquatic weeds. Since water hyacinth is floating, the eggs get attached on the roots only. The egg loaded aquatic weeds are collected in morning hours and kept for incubation in hatching hapas or directly spread in well prepared nursery ponds. However, in nursery spread eggs the spawn survival is very poor than hapa hatching. This method has certain disadvantages like: difficult to estimate eggs, egg predation by pond animals, poor egg fertilisation etc.
Hapa breeding:
Brood fish are reared either in separate ponds or in composite fish culture ponds. Brood fish are netted out to segregate mature males and females. They are weighed and kept in breeding hapa containing suitable egg collectors in evening hours. Generally 3-4 kg Hydrilla/ kg female fish is used as egg collector. Males and females are kept in ratio of 1:1 by weight. They breed naturally in hapa after 6-8 hrs. In less suitable condition fishes are injected with inducing hormones to ensure breeding. After spawning, the females are weighed to estimate the egg release. About 12-15 per cent of the weight difference goes towards faecal matter of fish and rest weight difference is due to egg release in ovary. One gram weight difference in ovary provides an estimate of 700 egg release. Egg attached 2-4 kg Hydrilla is spread per inner hatching hapa. Depending on water temperature, hatching takes place in 2 days and inner hatching hapas are removed in 3 days. After 4-5 days, spawn are collected for stocking in nursery ponds.
Hatchery breeding:
Some of the village hatchery owners use breeding pools for common carp spawning. They use nylon threads or plastic threads or plastic nets or Hydrilla or water hyacinth as egg collectors. Egg incubation is carried out in hatching pools.
Indian and exotic major carp spawn production
Indian and exotic major carp spawn production
Hapa breeding:
In remote villages brood fish are grown in composite fish culture ponds. During monsoon season they are netted out and fully mature males and females are selected. Breeding hapas are fixed in composite fish culture ponds having common carps. Presence of common carp, prawns and crabs cause severe damage to carp eggs in breeding hapas. Hence, to avoid hazards of loss of viable eggs, the breeding hapas are fixed inside the net enclosure. Generally for one female two males are used. Intra-muscular and/or intra-peritorial injection is administered to brood fish during June-October.
Females are injected with PG extract or glycerine extract of PG twice but males are injected only once. First dose is given in the evening hours to female @ 5-6mg/kg and second dose after 4-6 hours of fi rst injection @ 8-16 mg/kg. Males are injected at the time of second dose of female @ 4-5mg/kg male. Presently synthetic hormones (ovaprim or ovatide) are used as inducing agents in rural areas. Both the males and females are injected only once.
These synthetic hormones are administered @ 0.2-0.5 ml/ kg female and 0.1-0.2 ml/kg male. After 4-6 hours of injection fish spawn. Fertilised eggs are identified and quantified at comma stage of embryos and hatching are done using hapa hatching device. Spawn are collected after 72-80 hours of hatching by filtering with inner hatching hapa with the spawn recovery of only 24-44 per cent of the fertilised eggs. The low recovery of spawn from hapa hatching device could be due to a combination of factors such as cutting of hapas by crabs and/or large freshwater prawns, entry of unwanted fishes in hatching hapas, presence of predatory cyclopoid copepods in hatching hapas and sudden change in water temperature, depletion of DO content, water bloom and cyclonic weather.
Hatchery breeding:
For hatchery breeding, brood stocks are maintained in separate ponds by stoking 1-3t/ha brood fish under scientific management. Brood fishes are injected with inducing hormones as mentioned in hapa breeding. In rural areas the spawning is done in breeding hapa and/or spawning pool but hatching is done in incubation pools.
Two-three year old carps weighing 2-5 kg are the best for hypophysation. “Eco-hatchery” is used by the village entrepreneurs. It includes overhead tank, spawning pools, egg collection chamber, incubation pools and spawn collection chamber. An overhead tank is generally made on the roof of single or double storied building and a water holding capacity of 5000 litre can supply water to spawning and incubation pools. Depending upon the requirements, the sizes of spawning pools vary. Spawning pool is 8-9 m diameter and 1.0-1.5 m deep with the provision of water circulatory system and shower.
Farmers use 20-30 kg female per spawning pool and produce 250-400 litres of carp eggs in one operation. These eggs are incubated in 3-5 hatching pools. Incubation pools are 3-4m inside diameter and 1 m deep. Generally 1 egg is incubated in one ml water. During egg incubation, farmers maintain water flow @ 2.5 l/sec. initially, @ 2.0 l / sec at twisting movements of embryos and @ 3.5 l/sec after hatching to get better spawn recovery. Farmers harvest 800,000 to 1,000,000 spawn/pool/operation. KVK/TTC, CIFA designed and fabricated portable FRP carp hatchery in 1989 with the maximum spawn recovery of 3,000,000 lakh / operation/pool, now modified and commercialised by CIFA and it is used by the village entrepreneurs to produce carp spawn. From hatchery breeding farmers get 80-95 per cent recovery from the viable eggs. By adopting circular carp hatchery some of the rural fish farmers changed into entrepreneurial seed producers.
Carp fry and fingerling rearing in rural areas
In rural area, spawn to fry nursing is carried out in smaller ponds of 0.02-0.05 ha (0.5-1.0m depth). In same perennial ponds fry, fingerling and/or yearlings are reared in succession during June-July, August-November and December-June respectively. Alternatively the ponds are stocked with carp fry and rearing of fingerlings and yearlings are continued in succession.
For rearing larger size carp fingerlings 0.05-0.1 ha with an average depth of 1.0-2.0m are preferred. Ponds shaded by trees are rendered unproductive by reduced sunlight. Accumulation of leaf litter and an excessive organic load in the pond further deteriorates water quality, adversely affecting carp and carp food organisms. At times, masses of foamy brown/white frog eggs, which tend to fall into ponds during rains, caused a proliferation of tadpoles.
Therefore, marginal trees and bushes are cleared before launching the seed raising programme. Pond embankments are renovated with the provision of secured inlet and outlet. Since backyard ponds are shallow and small, aquatic weed clearance is completed manually by rural farmers. Predatory animals/ fishes and weed fishes are eradicated by de-watering and drying the ponds or application of suitable piscicides. Raw cattle dung is applied as basal manure in ponds. To enhance the fertilisation effect liming is done. For sustained production of natural fish food organisms a mixture of de-oiled cake, cattle dung/ bio-gas slurry and single super phosphate or a multiplex pre mineral mixture and vitamins are used in liquid forms before 4-5 days of spawn stocking.
Fry are harvested and/or thinned in phases according to the local demand, allowing an extended period of rearing (14-44 days) in rural area. Prolonged retention of fry in nursery ponds adversely affects the fry survival. Fry recovery is 20-40 per cent. Stocking spawn at shallow water depth (35-45 cm) followed by phased increase of water level at 3 – 4 days intervals, results higher fry recovery of 50-70 per cent. Fortification of micro-nutrients in artificial feeds is also enhances the growth and survival of fry. A commercially available multiplex pre-minerals mixture with vitamins accelerates plankton production and fry survival in nursery ponds. In case ponds are used for fry rearing, fry are harvested by repeated netting on day 15-20 of stocking.
At times, two crops of fry are taken. After fry harvesting, the ponds are fertilised with the mixture of above manure to produce adequate natural fish-food organisms. On day 2 or 3 of fertilisation, the fresh fry are stocked along with residual fry in such a way to maintain the density of 300,000-500,000/ ha. Later a mixture of above fertilisers is applied in liquid form at weekly or fortnightly intervals. Fingerlings are also fed traditionally and harvested by repeated netting after three months of rearing.
Large sized fingerling and yearling production
Yearlings are produced traditionally in village ponds. When farmers fail to sale their fingerlings and they continue to rear them up to May-June. Before monsoon, when ponds are prepared for next fry rearing crops, farmers harvest stunted fish for consumption as they are grown with reduced nutrient uptake. But now a days with the increased awareness of yearlings significance as stocking materials, it is being sold at pond site for grow out fish culture.
When stunted fingerlings are kept on a high quality diet they grow rapidly leading efficient body weight. Some of the village fish farmers produce yearlings and/or stunted fingerlings with improved management on commercial scale. In this, the fingerlings stocked in well prepared ponds at high density July-August. Yearlings are also reared by stocking appropriate carp fingerlings along with residual stock of fingerlings. During culture period ponds are fertilised monthly once. Fingerlings are fed with the mixture of ground nut oil cake and rice bran in the ratio of 1:1 by weight @ 4-6 per cent of the body weight. Complete harvesting of yearlings is done by repeated netting from May-June. Adopting this management the farmers are producing 3-5 tonnes of yearlings every year.
Nursery Pond Management
Small water bodies of 0.02-0.10 ha with depth of 1.0-1.5 m are preferred for nurseries though areas up to 0.5 ha can be used for commercial production. Drainable or non-drainable earthen ponds and cement cisterns are the different systems used for nursery rearing of fry.
The different steps involved in nursery raising of fry are discussed hereunder.
Pre-stocking Pond Preparation
Clearance of aquatic vegetation: Abundant growth of vegetation is undesirable in fish ponds as they absorb nutrients arresting the pond productivity, help in harbouring the predatory and weed fishes/insects hindering the free movement of fish and netting operations. Hence aquatic weed clearance is the first operation in pond preparation. Generally, manual methods are only used in nursery and rearing ponds, as they are shallow and small in size. In bigger ponds mechanical, chemical and biological methods can be used for eradication of aquatic weeds.
Eradication of predatory and weed fishes: Various predatory/weed fishes besides predatory animals like snakes, tortoises, frogs, birds, otters, etc present in ponds pose problems for survival of young fishes besides competing them for space and oxygen. Dewatering and drying the ponds or application of suitable piscicides are the methods adopted for eradication of predatory and weed fishes. Application of mahua oil cake @ 2,500 kg/ha-m three weeks before stocking of fish seed are suggested. The oil cake besides acting as piscicide also serves as organic manure after decomposition and adds to natural productivity. Application of commercial bleaching powder (30% chlorine) at dosage of 350 kg/ha-m of water is effective in killing the fishes. The quantity of bleaching powder can be reduced to half with the combination of urea @100 kg/ha-m, applied 18-24 hours before the bleaching powder application.
Pond fertilization :
Planktons are the preferred natural fish food organisms that are produced by fertilizing the culture ponds. The ponds used for seed production are first limed after the removal of unwanted predatory and weed fishes depending on the pH of soil. After liming, the ponds are treated either with organic manures such as cowdung, poultry dropping or inorganic fertilizers or both, one following the other. Mixture of groundnut oil cake at 750 kg, cowdung 200 kg, and single super phosphate 50 kg/ha is found to be very effective in production of desired plankton. Half of the above amounts, after being mixed thoroughly by adding water to make a thick paste is spread throughout the nursery 2-3 days prior to stocking. The rest amount is applied in 2-3 split doses depending on the plankton level of the pond.
Control of aquatic insects :
Aquatic insects and their larvae compete for food with the young growing fish and also cause large-scale destruction of hatchlings in nurseries. Application of soap-oil emulsion (cheap vegetable oil @ 56 kg/ha with 1/3 its weight of any cheap soap) is a simple and effective method to kill the aquatic air-breathing insects. Kerosene @100-200 l or diesel @75 l and liquid soap @ 560 ml or detergent powder @ 2-3 kg per hectare water area can be used as substitute to make the emulsion.
Stocking
After three days of hatching, the spawn are transferred to the nurseries. The stocking is done preferably during morning hours by acclimatizing them to the new environment. The normal density of spawn recommended for earthen nursery is 3-5 million/ha. However, higher densities of 10-20 million/ha can be followed in cement cisterns. In nursery, monoculture of carp species is usually recommended.
Post-stocking Pond Management
The phase fertilization is done in 2-3 split doses during the culture period of 15 days as discussed earlier. Finely powdered mixture of groundnut oil cake and rice bran at 1:1 ratio by weight are provided as supplementary feed @ 6 kg/million for the first 5 days and 12 kg/million spawn per day for the subsequent days in two equal installments. With adoption of scientific methods of rearing, the fry attain the desired size of 20-25 mm with survival of 40-60% in 15 days rearing period. Since nursery-rearing period is limited to 15 days, the same nursery can be utilized for multiple cropping, at least for raising 2-3 crops in case of earthen ponds and 4-5 crops in case of cements cisterns.
Fry-Fingerlings Rearing Pond Management
Ponds of comparatively bigger in size than that of nurseries and preferably up to 0.2 ha area is used for rearing pond, i.e., for rearing fry to fingerlings. The different steps involved are as follows:
Pre-stocking Pond Preparation
The practices of pre-stocking pond preparation viz., clearance of aquatic vegetation and eradication of predatory and weed fishes are same as discussed in nursery pond management, while measures for control of insects are not necessary in case of rearing pond management. The ponds are fertilized with organic manures and inorganic fertilizers, the doses of which depend upon the fish poison used. If mahua oil cake is used as fish poison, the amount of cowdung application is reduced to only 5 tonnes/ha, but with other poisons having no manurial value, cowdung is applied generally at the rate of 10 tonnes/ha. While about one third of the dose is applied as basal dose 15 days prior of stocking, rest are applies fortnightly doses. Urea and single supper phosphate @ 200 kg and 300 kg/ha/year, respectively are also recommended for fortnight application in split doses as inorganic fertilizer source.
Stocking of Fry
Determination of the rate of stocking depends mainly on the productivity of the pond and the type of management measures to be followed. The normal stocking density of fry suggested for rearing ponds is 0.1-0.3 million/ha. While nursery phase is limited to monoculture, rearing phase involve polyculture of different carp species similar to that of grow-out production.
Post-stocking Pond Management
A feeding rate of 5-10% followed for fingerlings rearing. While in most of the cases the supplementary feed is limited to the mixture of groundnut oil cake and rice bran at 1:1 ratio by weight, non-conventional ingredients can also be used to compound the feed. When grass carp are stocked, duckweeds like Wolffia, Lemna and Spirodela are to be provided. Maintaining water levels of about 1.5 m depth and intermittent fertilization as mentioned earlier are the other management measures suggested. With adoption of scientific methods of rearing, the fingerlings attain 80-100 mm/8-10 g with a survival of 70-90% under rearing pond conditions
