PRODUCTION AND SURVIVAL OF HYBRIDS OF CLARIAS GARIEPINUS AND HETEROBRANCHUS SPECIES UNDER HATCHERY CONDITION

Abstract

ABSTRACT

Hybridization is a genetic improvement technique in the aquaculture industry, which has been recognized as a tool to enhance production intensities and efficiency, for food security and employment generation. This study evaluated the production and survival of hybrids of Clarias gariepinus and Heterobranchus species under hatchery conditions. Twenty gravid broodstocks of C. gariepinus (CG), H. bidorsalis (HB) and H. longifilis (HL) with average weight (531.67±7.55 g) were cultured for three months before selecting twelve for hybridization. The crosses of CG (1100.00±57.74 g), HL (1200.00±57.74 g) and HB (1150.00±28.87 g) were carried out using ovaprim at 0.5 ml per kg body weight of female fish. The hybrids of HL♂ x HB♀ (T1), HB♂ x, HL♀ (T2), HB♂ x CG♀ (T3), CG♂ x, HB♀ (T4), HL♂ x CG♀ (T5) and CG♂ x HL♀ (T6) formed the triplicated treatments which were cultured for ninety days. The data obtained such as growth parameters, fertilisation and hatching rates among others were subjected to one-way analysis of variance using Statistical Products and Service Solutions (SPSS), while treatment means were separated using Duncan Multiple Range Test (DMRT). The growth response of the broodstocks showed no significant difference (p>0.05) in all the parameters. H. longifilis had the highest measurable values of final weight (1200.00±57.74 g), weight gain (680.00±46.19 g), specific growth rate (0.93±0.03 %/day) and relative growth rate (130.50±5.99 %), while the least values of final weight (1100.00±57.74 g), weight gain (555.00±65.26 g), specific growth rate (0.78±0.08 %/day) and relative growth rate (102.40±13.55 %) were recorded in CG. Results indicate significant differences (p<0.05) in the values of weight of stripped eggs, number of eggs per gram and fecundity of the fish among the treatments. The highest values for weight of stripped eggs (183.33±8.82 g), highest number of eggs per gram (741) and fecundity (133.31±3.06) were recorded in T3. The highest significant values for number of eggs fertilized (11577), fertilization rate (83.67 %) and hatching rate (66.67 %) were recorded in T3, T2 and T1, respectively. The lowest values of fertilization rate (70 %) and hatching rate (53.33 %) were observed in T5 and T6, respectively. The highest percentage survival (87.67 %) was recorded in T2 while T6 recorded the lowest percentage survival value (44 %). The trend of percentage mortality was T6>T4>T3>T5>T1>T2. The growth response showed no significant difference (p>0.05) in the values of initial weight, specific growth rate, daily growth rate, mean growth rate and relative growth rate among the treatments but had significant differences (p<0.05) in the values of final weights and weight gain among the treatments. Fish in T3 had the highest final weight (5.44 g) and weight gain (5.28 g) while fish in T6 had the least values of final weight (4.12 g) and weight gain (4.00 g). Water temperature, nitrate, turbidity, conductivity and total solids showed no significant difference at p>0.05. This study revealed that, the production and survival of C. gariepinus and Heterobranchus species under hatchery conditions was viable and could be sustainable based on the breeding performance and survival rates recorded.