Size composition in population of African catfish (Clarias gariepinus) fingerlings produced in the hatchery
Size composition in the rearing of Clarias gariepinus is integral. Four induced breeding exercises, referred to as the treatments (Trts) were carried out. Trt1 (700:1200), Trt2 (800:1500), Trt3 (800:2000) and Trt4 (1000:2000). In each treatment, 40g of eggs was incubated and replicated thrice, the experiment lasted for 50 days. Fecundity was highest in Trt3 and 4 (133,200). Latency period was highest in treatment 4 at 11hrs 20 minutes, fertilization rates were the same in all the treatments, percentage hatching rate was significantly different (P˃0.05) only in Trt1. In Trt4, the initial weight, growth rate and weight gain were significantly (P˂0.05) higher than Trt3 and the same lower value in Trt1 and Trt2. Specific growth rates showed no significant difference (P˃0.05) among the treatments. The relative growth rates in Trt1 and Trt2 were significantly higher (P˃0.05) than Trts3 and Trt4. Percentage survival ranged from 47.0±0.74 to 54.0±0.47 and was highest in Trt4. Apart from the “shooters/jumpers” three size classes were observed in the stock composition. The highest percentage size class was the medium size followed by the small size and least was the big size. The physico-chemical parameters measured were temperature, pH, dissolved oxygen concentration, NH3, NO2 and nitrate.
Keywords: African Catfish, size composition and variation, catfish stock, hatchery