24 DECEMBER 2017 • WORLD AQUACULTURE • WWW.WAS.ORG Role of Genetically Improved Seed Fish seed accounts for 5-10 percent of production costs and stocking good-quality seed is indispensable to the expansion of aquaculture. Culture practices such as stocking of poor-quality seed and mixed breeding of carps in the same hatching pond at the same time results in production of hybrid seed that is genetically degraded and grows slowly, with low production and less profit for farmers. Inbreeding depression is also observed in most carp hatcheries because of repeated use of the same broodfish without occasional replenishment. There is a lack of genetic norms in most hatcheries of India, accounting for production losses from poor-quality fish seed. Genetically improved seed is a suitable alternative to overcome problems associated with poor-quality seed. It can also contribute to higher yield per unit area without affecting the other indigenous species under cultivation. The adoption of genetically improved strains with higher genetic gain will increase fish production, enhance profitability, lower fish price, increase consumption and improve fish farmers’ household economy (Mahapatra et al. 2014). Genetically Improved Jayanti Rohu Selective breeding of rohu in India was initiated in 1992 by the Indian Council of Agricultural Research - Central Institute of Freshwater Aquaculture (ICAR-CIFA) in collaboration with the Institute for Aquaculture Research (Akvaforsk), Norway, with a mandate to improve the growth rate of rohu. Rohu was selected as the candidate species for selective breeding due to its high consumer preference, relatively good growth performance in multispecies carp culture system and low susceptibility to diseases. Founder base populations for the selective breeding program were collected from five riverine sources (Ganga, Yamuna, Brahmaputra, Sutlej and Gomati) and from ICAR-CIFA farm stock as the sixth stock source. The selective breeding protocol was performed through a combined selection method and 50-60 full-sib families were produced every year on average. The improved fish is popularly known as Jayanti rohu because it was first released in 1997 during the 50th anniversary of Indian Independence (Swarn Jayanti). After success of the Jayanti rohu that was selected for greater growth, disease resistance against Aeromonas hydrophila was added as a second trait of selection to the breeding program. A wide range of variation in survival was observed among different families of rohu in the challenge test. Production of full-sib families of rohu and mass production of genetically improved rohu spawn was carried out in a specialized hatchery constructed at ICAR-CIFA, Kausalyaganga, Bhubaneswar. The hatchery complex consists of six units with overhead tanks, spawning pool, male broodfish cistern, acrylic glass jars for incubation of fertilized eggs, a hatchling collection cistern and a circular hatching pool for mass incubation of fertilized eggs. This hatchery was developed to produce individual full-sib families from fertilized eggs to spawn. A nested mating design (two males nested within a female or vice versa) was used. Every year, full-sib families were produced as per the mate allocation plan, avoiding mating of close relatives to minimize inbreeding depression. Full-sib families were reared separately until tagging in a partitioned nursery pond. Passive Integrated Transponder (PIT) tags were used for individual identification of fingerlings from different families (Das Mahapatra et al. 2001). After tagging, fingerlings (10-15 g) were transferred and reared in communal ponds that were sampled periodically to assess fish growth. The salient features of Jayanti rohu are substantial additive genetic variance for growth and negligible heterosis (hybrid vigor) for growth. The ranking of full-sib families for growth is highly consistent in monoculture and polyculture. An average genetic gain of 18 percent per generation has been obtained after eight generations of selection (Mahapatra et al. 2016). Field trials and onfarm trials have confirmed the growth potential of improved Jayanti rohu. Impact assessment study further confirmed the superior growth efficiency of the Jayanti strain over normal rohu. Benefits to Farmers The production cost of Jayanti rohu is not very high because it does not require high protein feed and can be cultured with locally made plant-based feeds with 25 percent protein level. The species is feed neutral and effective under all culture practices. The daily ration of feed may be given in two instalments at 3-4 percent of body weight. Stocking density should be moderate (6000-7000 fingerlings/ha) to obtain higher individual yield. Periodic health monitoring is also essential. Jayanti rohu requires two fewer months to attain market size compared to local rohu. It also fetches a better market price due to attractive coloration. Jayanti rohu is not a genetically modified organism (GMO) and so it is not harmful to the biodiversity of aquatic environments. Procedure for collecting eggs from female Jayanti rohu broodstock. Egg batches collected from individual female Jayanti rohu broodstock.
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