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Tital: Production and Utilization of Stunted Seed for Fish Yield Enhancement INTRODUCTION: Stunted fish fingerlings - Stunted growth fingerling is when the fish physically appears to stop growing either because of poor diet, poor water quality or by being in a tank that's too small for it but have not yet attained full growth potential. Rearing of fish fries /fingerlings at higher stocking density fed with natural food for 10-12 months produces stunted growth fish fingerlings. Such stunted seed when stocked in the culture pond would compensate for the growth lost during the stunting period and attain a weight of 1 kg. In India fish culture has witnessed a rapid expansion in the last 2-3 decades. As the farmers became familiar with the technology of fish culture, they have modified the technology to suite their needs. Among the different modifications adopted by the farmers to suite their needs, use of stunted carp fingerling round the year is important. The stunted fingerling when stocked in grow-out ponds at normal stocking density with optimal feeding and fertilization exhibited compensatory growth in terms of weight gain and survival in shorter culture period. Application of compensatory growth phenomenon by using stunted carp fingerling has been proved to have greater potential in increasing fish production.

Some study of different scientist: Production of stunted fingerlings is achieved by stocking normal fry at high stocking density with sub-optimal feeding and manuring (Veerina et al., 1993). Radheyshyam and Saha (2009) reported fast growth in stunted fingerlings of carps. Nandeesha et al. (1994) studied the growth performance of stunted yearlings of rohu and reported 25% protein and 37% carbohydrate as optimum dietary requirements. Growth and survival of stunted fingerling is dependent on level of protein in the diet (Kumar et al., 2011). Swamy (2004) and Kumar et al. (2011) reported good growth performance in stunted fingerlings of mrigal and rohu at 25% dietary protein level. The growth performance of stunted fingerlings of C. catla, in the present study are comparable with works of Nandeesha et al. (1994) on stunted yearlings of rohu, Swamy (2004) and Kumar et al. (2011) in stunted fingerlings of mrigal and rohu respectively. The decrease in growth of stunted fingerlings of C. catla with increasing level of protein above the optimum in the present study is similar to those reported for catla (Dars et al., 2010), grass carp (Dabrowsky et al., 1977) and stunted fingerlings of rohu (Kumar et al., 2011).To overcome the problem of seasonality and availability, carp farmers of Andhra Pradesh, India started the system of producing “stunted yearlings”, which has now become very popular (Veerina, Nandeesha and Rao, 1993; Mohan and Bhatta, 2002).

Compensation of growth: According to Russel and Wootton (1992), the compensatory growth is defined as the ability of a dietary restricted animal to achieve its normal body weight and form by a growth spurt or re-alimentation. Compensatory growth is a process in which animals that have been “stunted” by an impoverished environment grow rapidly and catch up with animals of similar age once the environment is optimal. Types of compensatory growth in fish as reported by different workers: Generally 4 types of compensatory growth occurs in fishes bellow these- 1. No compensation: No growth recovery 2. Partial compensation: 25-75% growth recovery as that normal fed groups 3. Full compensation: 100% growth recovery 4. Over compensation: More growth recovery than the normal fed groups

Compensatory growth in case of Animal: Compensatory growth In case of Fish: Lipolysis and gluconeogenesis increased during feed restriction and the levels of insulin and thyroid hormones are decreased. After feed restriction, animals enter a phase of compensatory growth, when levels of anabolic hormones are increased to promote somatic growth rather than storage of energy reserves as fat (Squires, 2003). Many authors suggested that the period of feed deprivation and refeeding can be used to increase feed conversion efficiency resulting more growth in fish (Ali et al., 2003; Nicieza and Alvarez, 2009; Jobling, 2010).

Advantages of compensatory growth in animal: Achieving compensatory growth of fish has several advantages in aquaculture such as- 1. It can save feed and labor costs. 2. Improve management of personal time. 3. Reduce water pollution/organic load. 4. Enhance growth and feed utilization. 5. The feeding strategies leading to compensatory growth of fish will be very useful technique for improving production efficiency and/or influence the composition of the saleable products. Why should go for Stunted Seed? Stunted seed have some advantages in aquaculture such as- 1. Carps are known to grow rapidly during the second year of their age. 2. Higher survival rate in grow out ponds. 3. More Immune to the diseases. 4. More tolerant to environmental fluctuations. 5. Require less time to reach marketable size (5-6 months). 6. Majority of seasonal water bodies dries within 5-6 months where fish rearing from advanced fries is not economical. 7. High growth rate & can be sold at higher prize. 8. Higher production and productivity. 9. Unhealthy seeds are perished during stunting periods, so we get only healthy seeds. 10. The use of stunted fingerlings will enable the commercial fish producers to have access to fingerlings all year round and therefore be able to stagger their harvest through the year. 11. This would enable the producers to harvest more than one crop of fish a year. 12. Stunted fingerlings will also enable farmers in temperate areas and areas with seasonal water supply to produce table-sized fish in a short duration of time. Basic principle for production of stunted fingerlings- Generally Carps are known to grow rapidly during the second year of their age and Recognizing the basic growth pattern, farmers have develop a technology to supply stunted fish seed that are aged, but have not yet attained full growth potential.

Suitable fish species for the production of stunted fingerlings: Generally fish species are to be selected for the production of stunted seed which have ability to compensate there growth during re-feeding such as-  Indian major carps- Catla, Rohu , Mrigal.  Exotic carps-Silver carp, Grass carp, Common carp.  Other commercially cultured species like tilapia, trout and other catfishes.

Technology used for production of Stunted fingerlings: For rearing larger size carp fingerlings pond size 0.05-0.1 ha with an average depth of 1.0-2.0m are preferred. For the purpose of stunning the seed are stocked @ 25000- 100000/ha and fed them with minimal amount of feed i.e. good enough for their survival. The stocking densities also based on the final growth desired for stocking in grow out ponds. At lower stocking density, the fish would attain a weight of 100-150 gm but at higher stocking density fish would reach to 25-50 gm. Pond management for production of stunted seed: Pre stocking management: Stunted fingerlings can be reared in ponds from 0.1-0.4 ha in size ranging in depth from 1.5-2.0 m. These ponds should retain enough water in the summer so that the fingerlings are not affected. The ponds need to be made free from weeds, weed fish, predators. Weeds take nutrients out of the water. They hinder the movement of the fish. They also reduce oxygen during the night and early in the morning. These weed has to be taken out manually by hand. If there are no weeds in the pond, for destroying predators and competitors first apply urea at 100 kg/ha where the water is 1 m deep. After 24 hours apply 200 kg of fresh bleaching powder/ha. Fish start dying within one hour of adding the bleaching powder. These fish can be harvested and eaten. It takes a week for the toxic effect of bleaching powder to go. After that application of lime @ 300-500 kg/ha either before rainwater filling or after for pH corrections and disinfection can be done. Then the pond preparation involves application of cow dung (@ 2.5-3 MT/ha) and mustard oil cake @350-400 kg/ha as organic manure, sporadic application of inorganic fertilizers viz., NPK mixtures @60-75kg/ha., urea@100-125kg/ha. to pond water to facilitate better natural fish food production. Stocking: The fish seed of mixed varieties of Indian major carps are commonly stocked after about 4-6 days of initial manure at densities of 4-5 lakh/ha. In sporadic instance grass carp, silver carp, common carp and others varieties like big head, calbasu, Puntius japonicus etc. are also reared. The ratio of different species in seed stocking vary in accordance to supply, availability and demand in the region. The stocking density used is also based on the final growth desired for stocking in grow-out ponds. For example, at lower stocking density, fish would attain a weight of 100-150 g, but at higher stocking density, fish would reach about 25-50 g. Seed stocking is generally done in the cool evening hours. In case of IMCs it is often recommended that these fish are stocked in the ratio 3:4:3. The best mix of the fry of Catla, Rohu and Mrigal depends on the pond. If there is a lot of debris on the bottom of a pond, more Mrigal (which is a bottom feeder) could be stocked or Common Carp added to the mix. If there are lots of submerged plants with tiny plants growing on them, which Rohu eat, then more Rohu could be added. Where a lot of succulent grasses are submerged, Grass Carp could be added to the mix. The stocking density is high for advanced fingerling production in perennial ponds because the target is slow growth and a fingerling that is small for its age. Post-stocking: The stocked fry are fed daily with minimal amount of feed, i.e. good enough for their survival. Feeding with mustard cake powder and rice bran is a common practice. Initial feeding is done by direct broad cast method twice a day, once during morning and evening; later adding the feed in dough form in the same place helps fish to feed efficiently. Feed level should be reduced if the weather is cool and increased in warmer weather. Liming the pond at 50 kg/ha during October-November and again during March-April is a must. Periodic fertilization with fresh cow dung (1,000 kg/ha) or a mixture of cow dung (500 kg/ha) and poultry manure (250 kg/ha) should be done every month. Feeding and application of the manure should be avoided on cloudy days when special attention must be paid to oxygen levels. Feeding and manuring should not be done on cloudy days or if the oxygen levels fall below the minimum requirement when the fish start coming up to the surface to gulp the air. Fry/fingerlings are reared in ponds for about 10-12 months when they usually attain 50–100 g in weight. During this period of stunting, weak and unhealthy seed are also eliminated from the system. Healthy seed which survive the stunting process are used for culture purpose. Stunted seed (fingerlings) transportation: Farmers have begun to use large PVC containers of 2000 to 3000 l capacity for transportation of seed. Tanks placed on trucks are filled with water and the conditioned fish seed are stocked in the tank. These tanks are connected with oxygen supply from the cylinder placed on the truck. Using this method, farmers are able to transport the seed over long distances without any mortality problem.

Farmers and researcher experience: 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. Ponds are fertilized monthly. 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. Experiment- 1. Experiments conducted in cisterns with rohu fingerlings, with one feeding @2% initial body weight of fingerlings for a period of 4- 5 months indicated the results shown below :-

Experiment- 2. Sub-project title : Protocol development for production of stunted carp seed and study of their compensatory growth response in culture system. Project code : I-80(c) Funding Agency : Institute-based Duration : April 2012 – March 2015 Project Personnel : P. C. Das (PI), K. N. Mohanta, B. Mishra and B. K. Pati Grow-out culture of stunted rohu fingerling under monoculture to evaluate the influence of duration and density of stunting on their production performance Fingerlings of rohu stunted at 20 and 40/m2 density for 2, 4, 6, 8, 10 and 12 months were stocked in six earthen ponds of 0.09 ha each with 720 fingerlings / pond (8000 fingerlings/ha). Each pond contained 50% of stock stunted at 20/m2 and 50% stunted at 40/m2. Among these stocks, 15 fingerlings from each density were tagged with electronic tag prior to their release in the pond so as to monitor the individual growth. All these fishes were reared subsequently for 12 months and their growth performance was recorded through monthly sampling. After 12 months of grow-out culture of each stunted duration group (Table 1), the study revealed similar type of length and weight gain in all the stunted groups irrespective of their duration of seed stunting. However, seed stunted at 40/m2 density in all duration groups showed only marginal and non significant increase in growth compared to those stunted at 20/m2. Absence of any convergence of the growth curves with regard to seeds with varied stunting duration revealed absence of compensatory growth capability in this species. Such results revealed the density and duration of seed stunting in rohu not to have any compensatory growth implication in the subsequent grow-out culture.

Grow-out culture of stunted rohu fingerling under polyculture to evaluate the influence of duration and density of stunting on producti on performance. Fingerlings of rohu stunted for 2-12 month at 20 and 40/m2 densities were stocked along with catla and mrigal under a grow-out polyculture study in a 0.09 ha earthen pond. Catla, rohu and mrigal were stocked at 3:4:3 ratio at a combined density of 8000 fingerlings/ha. The rohu fingerlings stocked in the pond consisted of 2 month stunted population, 50% of which were stunted at 20/m2 and the rest at 40/m2 density. Among these, 10 fingerlings from each density were tagged with electronic tag prior to their release. Subsequently in every two months, 20 number of non-tagged rohu from the pond were replaced with 10 tagged rohu from two densities and drawn from population of 4, 6, 8, 10 and 12 months stunted groups. The grow-out study continued for two years so as to allow every stunted group of rohu to have at least 12 months grow-out culture. Sampling of the three species is being carried out at monthly intervals. From the catla and mrigal stock, 25 fishes from each species are being sampled to record their length and weight. Similarly, 25 non-tagged rohu and all tagged individuals from different stunting duration groups were sampled every month to keep the record of their growth. During the subsequent polyculture , no convergence of growth curves was observed among rohu stunted for greater duration (4-12 months) as compared to the two months stunted group. All the stunting duration groups showed almost similar growth performance depending on their grow-out culture duration (Table 2), but irrespective of their duration of seed stunting. Besides, there was no growth difference between the fingerlings stunted at the two densities in any of the stunting duration group. Such results, similar to our findings in monoculture, reiterated absence of any compensatory growth implication of the stunted seed with regard to duration of seed stunting in the subsequent grow-out culture. Evaluation of growth performance of stunted versus normal fingerling in grow-out monoculture of rohu. In the earlier two mono- and poly-culture studies, the need to use rohu seed from the same population for stunting has led to stocking of grow-out ponds at different times of year only after completion of then 2-12 months stunting duration. There was a need to refine our findings of the absence of the compensatory growth in these studies against the seasonal effect, if any, that might have interfered during the growth of the stunted seed stocked at different times of the year. Therefore, another study was designed which aimed to evaluate the grow out performance of rohu fingerlings stunted at40/m2 density for 12 month against same size normal fingerlings, tore – examine the compensatory growth process in the stunted individuals. Ponds (0.09 ha) have been stocked at 8000 fingerlings/ha where the stock comprised 50% each of stunted and normal fingerlings. Twenty five fingerlings from each group were tagged with electronic tag. Growth performance of fishes is being studied through monthly sampling. Conclusion: Most importantly, the survival of such stunted fish is almost 100 percent, except for mortalities due to other environmental conditions. These advanced fingerlings can be stocked in perennial ponds, which have a resident population of competitors and predators (that cannot be removed), or in seasonal ponds which hold water for only 6-8 months. This technology of stunting fish seed developed by farmers is considered as one of the most important practical solutions found by farmers to address the problems related to fish growth and yield. In commercial carp culture systems in many parts of India, this practice has completely replaced the conventional system of stocking fingerlings, and there is considerable improvement in health, survival and production. The use of stunted fingerlings will enable the commercial fish producers to have access to fingerlings all year round and therefore be able to stagger their harvest through the year. This would enable the producers to harvest more than one crop of fish a year. Stunted fingerlings will also enable farmers in temperate areas and areas with scanty water supply to produce table-sized fish in a short duration of time. As stated earlier, farmers are now able to obtain, most commonly an average yield of 8 tonnes/ha and some of the progressive farmers obtain a yield of more than 13 tonnes/ha/year. But Stunting carp fingerlings beyond 4 months do not lead to any significant compensatory growth during the grow out period.