The daily weight gain, growth rate and length-weight relationships of Clarias gariepinus, Heterobranchus longifilis and their reciprocal hybrids (Pisces: Clariidae) reared under ambient environmental conditions
A comparative study was conducted on some growth parameters of Clarias gariepinus, Heterobranchus longifilis and their reciprocal hybrids in laboratory aquaria. This was aimed at determining the best aquaculture candidate amongst them. The growth parameters compared were: The condition indices, specific growth rates, average daily weight gain as well as their length-weight relationships. The four fish-types studied were contained, each type, in one of four different aquarium tanks which had equivalent ambient physico-chemical conditions. In terms of growth in length, the Clarias gariepinus♂ X Heterobranchus longifilis♀ hybrid (Cg ♂ X Hl♀), had the highest final length and weight (4.20 cm, 1.13 g ) while Clarias gariepinus (Cg) had the least ( 2.58 cm, 0.22 g). Heterobranchus longifilis (Hl) and the Clarias gariepinus ♀ X Heterobranchus longifilis ♂ hybrid (Cg♀ X Hl♂ ) had growth values falling between these two extremes (3.33 cm, 0.57g; 3.50 cm, 0.70 g) respectively. There was, however, no significant difference (P ˃ 0.05) between these values although a regression analysis of the length-weight relationships in the four fish-types revealed a significant positive correlation between fish length and fish weight. With respect to the condition indices, Cg had 1.10; Hl,1.12; Cg♀ X Hl♂, 1.14 and Cg ♂ X Hl♀, 1.17 (P ˂ 0.05). For specific growth rates (G%), Cg had 5.50% which was the least specific growth rate recorded amongst the fish-types studied while the Cg ♂ X Hl♀ hybrid had the highest, (8.44%). The other fish-types had values falling in between these two. There was also no significant difference between them, (P ˃ 0.05). With respect to the average daily weight gain, Cg still had the least value (0.06g) while the Cg ♂ X Hl♀ hybrid had 0.14 g, being the highest value.Hl had 0.12 g and Cg♀ X Hl♂ had a value of 0.13 g. No significant difference was recorded between them (P ˃ 0.05). In all cases, however, the face values obtained for the Cg ♂ X Hl♀ hybrid were always the highest and those of Cg, always the least. These results have been discussed.
Key words: Weight gain, specific growth rate, length-weight relationships, condition indices, catfish hybrids, ambience