Selected egg parameters and hatching time of African catfish (<i>Clarias gariepinus</i> and <i>Heterobranchus longifilis</i>)

Abstract

Egg weight, diameter and mean number per gram were determined for fertilized eggs from broodfish of Clarias gariepinus and Heterobranchus longifilis and F₁, hybrid broodfish (C. gariepinus x H. longifilis). Mean egg weight was least in C. gariepinus (1.30 mg) followed by H. longifilis (1.80 mg) and highest in the F₁ hybrid broodfish (2.20 mg). Egg diameter followed a similar trend 1.10-1.20mm for C. gariepinus, 1.20-1.60 mm for H. longifilis and1.50-1.90 mm for the F₁ hybrid broodfish. The 3-day-old post-yolk fry measured 6.20 mm in C. gariepinus and H. longifilis but was 7.00 mm in the F₂ and backcross, F1x H. longifilis. Hatching rate duration was determined for fertilized eggs that were used for the F₁ cross (C. gariepinus x H. longifilis) under the harmattan period, dry season and rainy season conditions. Hatching rates ranged from 74.40-84.00% in harmattan period, 66.80-86.00% in dry season and 64.80-83.20% in the rainy season. Hatching was earliest in the dry season (18.42- 29.42h after fertilization) and occurred very late in the harmattan period (27.75-42.20h after fertilization). Dissolved oxygen concentration ranged between 4.00 mg and 5.70 mg/L in all the experimental tanks.

Keywords: Egg parameters, C. gariepinus, H. longifilis, F₁ hybrid, hatching