African catfish, Clarias gariepinus is one of the predominant and viable cultivable fish species in Nigeria. This fish species can easily be propagated by induced breeding in the hatchery. However, the stickiness of the eggs during artificial propagation has been a major bottleneck affecting the hatching of the eggs and invariably the survival of prospective larval. This constraint discourages many fish breeders in Nigeria from artificial propagation of C. gariepinus. Sweet potato (Ipomea batatas) is widely cultivated in Nigeria. It is also a stable and starchy food. Hitherto, there are no information on the use of starch suspension of I. batatas for the removal of eggs stickiness. Thus, the aim of this study was to determine the use and efficacy of I. batatas as egg desticking agent. The specific objectives were to determine the optimum concentration and immersion period that efficiently removed eggs stickiness, increase hatching and survival of larval.
Post fertilized eggs of C. gariepinus were collected in 0.25g aliquots (175eggs) into 20 experimental spawning bowls for each treatment replicate. They were rinsed in three concentrations of I. batatas starch suspension treatments (0.5%, 1.0% and 1.5%) and Control (0%), at immersion periods {5, 10, and 15mins}.
The 0.5% concentration level had egg detachment between 36% and 88%, 1.0% had egg detachment between 33% and 41% while 1.5% had egg detachment between 25% and 66%. The result shows no regular pattern across the concentration levels and immersion periods. The incubation periods of the post fertilized eggs was not affected by the immersion periods but by concentration levels. There was significant difference (P<0.05) across all concentration levels but there was no significant difference (P>0.05) across the immersion periods. The hatchability of post fertilized eggs in 0.5% concentration level decreased as immersion period increases while 1.0% and 1.5% had highest hatchability at 5 minutes. A deformed larva was found in 1.0% concentration level at 10 and 15minutes immersion periods. There was no regular pattern of increase in the larval survival with increase in immersion period but 0.5% and 1.5% concentration levels had highest larval at 15minutes while 1.0% had highest larval survival at 5minutes. There was no significant difference (P>0.05) across all concentration levels but there was significant difference (P<0.05) across the immersion periods.
Based on the results of this study, the optimum concentration level and immersion periods of I. batatas starch suspension for detachment of eggs of African catfish, C. gariepinus are 0.5% and 10minutes, respectively.