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

A diallelic cross between two strains [Layo strain (LS) and Noun strain (NS )] of the catfish Heterobranchus longifilis Valenciennes was carried out un der controlled hatchery conditions to estimate their reproductive performan ce and aquaculture potential in terms of fertilizability, hatchability, sur vival, growth and heterosis. The average fertilization rate of all mating g roups was as high as 90.4%, the fertilization rate of the purebred NS (95.2 %) being significantly higher than that of the purebred LS or the reciproca l crosses (P < 0.05). The average hatching rate of all genetic groups was a s high as 84.7%, the hatching rate of NS (89.4%) being significantly higher than that of the purebred LS or the reciprocal crosses (P < 0.05). The mea n survival rate of all crosses from hatching up to the onset of exogenous f eeding 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 to 15 days of age, NS displayed a signifi cantly 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 surv ival rate (mean 84.7%) between the four crosses at the end of the larval re aring period. During the juvenile rearing phase, the mean growth performanc e of all crossbreds was similar to that of the purebred LS and significantl y different from that of the purebred NS (P < 0.001). The final individual weights attained by LS, 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 cro ssbred 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 display ed about 15.1% heterosis in mean body weight relative to the fast-growing p urebred LS. It was concluded that cross-breeding of H. longifilis strains c ould be advantageous because of the hybrid vigour in the progeny.