Fertilization, hatching, survival and growth rates in reciprocal crosses of two strains of an African catfish Heterobranchus longifilis Valenciennes 1840 under controlled hatchery conditions

摘要

A diallelic cross between two strains [Layo strain (LS) and Noun strain (NS)] of the catfish Heterobranchus longifilis Valenciennes was carried out under controlled hatchery conditions to estimate their reproductive performance and aquaculture potential in terms of fertilizability, hatchability, survival, growth and heterosis. The average fertilization rate of all mating groups was as high as 90.4%, the fertilization rat of the purebred NS (95.2%) being significantly higher than that of the purebred LS or the reciprocal crosses (P < 0.05). The average hatching rate of all genetic groups was as high as 84.7%, the hatching rate of NS (89.4%) being significantly higher than that to the purebred LS or the reciprocal crosses (P < 0.05). The mean survival rate of all crosses from hatching up to the onset of exogenous feeding stood at 94.2%, without showing a significant difference (P > 0.05) between the crosses. During the larval rearing period, which extended from the onset of exogenous feeding up to15 days of age, NS displayed a significantly lower growth rate (P < 0.001) than that of the purebred LS and their reciprocal hybrids. There was no significant difference (P > 0.05) in survival rate (mean 84.7%) between the four crosses at the end of thelarval rearing period. During the juvenile rearing phase, the mean growth performance of all crossbreds was similar to that of the purebred LS and significantly different from that of the purebred NS (P < 0.001). The final individual weights attained byLS, NS, LS X NS and NS X LS were 3.31, 0.71, 3.97 and 3.66 g respectively. The increase in weight attained by the fast-growing crossbred LS X NS was 562.2%, 20.4% and 8.7% more than that of NS, LS and NS X LS respectively. The survival rate of NS (57.1%)was significantly lower (P < 0.001) than that of all the rest of the crosses. The crossbreds displayed about 15.1% heterosis in mean body weight relative to the fastgrowing purebred LS. It was concluded that crossbreeding of H. longifilis strains couldbe advantageous because of the hybrid vigour in the progeny.