Author(s): Paul Sagwe Orina, Joseph Rasowo, Elijah Gichana, Benard Maranga, Harrison Charo-Karisa

Abstract: Broodstock were collected by use of an electro-fisher from four rivers; Mara, Migori, Nyando and Yala and transported to KMFRI Sangoro hatchery for spawning. They were subjected to a 3 x 2 x 4 factorial design (3 temperatures x 2 ovaprim dosages x 4 populations) with 72 treatments (3 replicates per treatment) in aquaria flow through system. Each replicate in every population were subjected to 22± 1°C, 26± 1°C and a control (no temperature regulation). Two ovaprim dosages (0.2 and 0.5 mlkg-1) administered to female brooders. Latency period significantly (p < 0.05) varied among treatments but remained the same among populations. There was no significant difference (p > 0.05) in latency period between the two ovaprim dosages (0.2 and 0.5 mlKg-1). However, temperature had a significant (p < 0.05) effect on the spawning time, brooders under 26±1 °C responded at 6-8 h, those under 22±1 °C responded at 12-18 h and the controls responded at 16-18 h. Fecundity significantly (p < 0.05) depended on fish size and river source. Mean fertilization and hatching rate were both dependent on temperature with temperature of 26±1 °C being the best performer for all populations. Ovaprim dosage had no effect on ovulation. Larval survival was directly dependent on temperature with 26±1 °C having the highest larval survival (89%), while the control had the least survivalrn(67%) but not significantly different from temperature 22±1 °C (71%). Yolk sac reabsorption was not significantly related to the population source and ovaprim dosage but was directly related to temperature with temperature 26±1 °C having the shortest time (18-24 h) post hatching. Results indicate that ovaprim dosage of 0.2 mlKg-1 and water temperature of 26±1 °C provides the optimal L. victorianus breeding conditions in captivity.

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