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Cold Shocking at 5oC AND 7oC in Triploid Production: Effects on Embryonic Development, Hatchability and Fry Performance in Clarias Gariepinus
Abstract
Production of genetically improved fast growing triploid Clarias gariepinus was carried out through cold shock application of fertilized eggs at 5oc and 7oc.The effects of the shock application on embryo survival, hatching time, hatchability and fry performance (fry survival and weight at critical growth stages) of Clarias gariepinus were investigated for commercial production purpose. Results revealed that the treatment reduced foetal survival from the 12th to 24th hour of incubation (p<0.05) and fragmentation of ovarian follicle under 5oc cold-shocked treatment. Hatching time was also reduced (p>0.05).Hatchability was significantly reduced (p<0.05) with 5oc cold shocked (T1) having the least value. Fry performance-Mean survival at completion of yolk sac and swim up stages and weight gain at 21 and 28days after hatching were significantly improved by the treatment (p<0.05).Cold shocked treatments performed better than the un-shocked while the 5oc cold shock gave the best performance. Weight after 28days of rearing were 0.179±0.02g, 0.087±0.12g and0.049±0.02g for T1 (5oC), T2 (7oC) and T3 (control) respectively. It was concluded that triploid produced by cold shock application especially of 5oc cold shock would enhance fry performance. However, intending commercial triploid breeders would need to compensate for high foetal mortality, delayed embryological processes and low hatchability.
