BIOLOGY AND AQUACULTURE POTENTIAL OF Labeo victorianus (Boulenger, 1901) UNDER DIFFERENT CULTURE SYSTEMS, DIETS AND STOCKING DENSITIES.

Abstract

A study on the biology and aquaculture potential of Labeo victorianus as an aquaculture candidate was conducted at KMFRI Sagana and Sangoro Aquaculture Stations. There was a significant spawning time difference between induced female brooders and those not induced with ovaprim® but no significant difference (F0.05,1, 118 = 1.27; P = 0.262; R2 = 0.985 ) between the two Ovaprim® dosages (0.2 and 0.5 ml Kg-1). Temperature, unlike river source and ovaprim® dosage had significant effect (F0.05,1,118 = 7879.6; P = 0.0001; R2 = 0.927 ) on the spawning time. Fecundity significantly (F0.05, 3, 120 = 248.25; p = 0.0001; R2 = 0.858) depended on river source which was also related to fish length and weight. Thereafter, a simulated transport experiment involving broodstock and fingerling weighing 100 ±3.2g, 5 ±1 g and 0.5 ±0.2 g were packaged in 5 L polythene bags with 1.5 L water at 400, 800 and 1200 g L-1, 120, 150 and 200 g L-1 and 12, 15 and 20 g L-1 respectively. Transportation durations within and across treatments had Un-ionized Ammonia increase with increased temperature and pH but remained within recommended ranges for warm water fish with no mortalities. A further 21 days aquaria and 28 days hapa experiments on 3 and 10 days old fry growth and survival were subjected to 3 stocking densities (100, 200 and 300 m-3) and 2 diets (Artemia® and starter feed- 40% Crude Protein). Unlike in hapas, diet and stocking density had a significant effect on growth and survival in aquaria with stocking density 100 fed using Artemia® posing significantly better length and weight gain. A polyculture experiment on 150 m2 ponds stocked at 3/m3 had tilapia and Labeo monoculture treatment ponds as controls while polyculture involved ratios 2:1 and 1:2 (Labeo : Tilapia). L. victorianus in treatment 2 (Lab2, Til1) had a significantly higher final weight (23.82± 8.05 g) as compared to treatment 3 (Lab1, Til2) whose final weight was 17.19± 5.05 g. Survival of polyculture treatment T3 had a significantly (P˂ 0.05) higher survival ( L= 49% and T= 87%) as compared to T2 (L= 31% and T= 69%). Finally, a 3 x 1 factorial design experiment (3 diets and 1 stocking density) of fingerlings weighing 11±1g was replicated in hapas at 22 m-3 over 60 days. Fast sinking feed had a significantly higher Daily Weight Gain (0.17), Final Weight Gain (21.32 ±7.61g) and a lower Food Conversion Ratio (1.38) than floating feed. However, the coefficient of determination (R2) was weak due to multicollinearity (F0.05, 11, 847 = 6.52; P = 0.0001; R2 = 7.81 %).The study findings therefore suggest that a temperature of 26 ±1°C and 0.2 ml Kg -1 Ovaprim® dosage is optimal for L. victorianus breeding, while a temperature of 18-23°C is ideal for all sizes and load densities on 24 h transport duration. Finally Labeo-Tilapia polyculture reared using sinking feeds is recommended but with a further culture systems and diet test for optimal growth and survival to be realized at commercial level.