Aspects of the Reproductive Biology of Hatchery-Raised Clarias Gariepinus I: Fecundity

Abstract

The fecundity of four batch weights (10 samples each) of gravid Clarias gariepinus weighing 60 ± 0.17159 g, 125 ± 0.15092 g, 250 ±0.20683 g and 500 ± 0.15670 g raised from the hatchery was investigated. The paired ovary of each fish was dissected out, weighed (g) and its length measured (mm).  Each paired ovary was stored in a solution of 1 % formalin in 0.6 % saline solution for at least 3 weeks for the solution to harden the eggs and remove egg clumping.  After 3 weeks, each paired ovary was torn apart on a 2 mm mesh circular fabricated sieve over a stream of water.  The eggs passed through the 2 mm mesh sieve into a receptacle.  Sub sample of the eggs from each paired ovary was taken, counted and all the eggs in each paired ovary were determined thereafter by volumetric method.  The total fecundity of 40 gravid fish studied ranged from 6,450 to 71,450 eggs per fish. The mean fecundities of the 60 g, 125 g, 250 g and 500 g fish were 8,501.9 ± 295.5, 13,364.0 ± 1734.3, 41,087.9 ± 12258.1 and 51,186.0 ± 13851.0 eggs respectively. The relationships between fecundity and fish weight (FW) (n = 40,  r = 0.8761), fish total length (TL) (n= 40,  r = 0.8266), fish ovarian weight (OW) (n = 40,  r = 0.7609), fish ovarian length (OL) (n = 40,  r =  0.7236), gonadosomatic index (GSI) (n = 40,  r = 0.5992) and fish condition factor (K)  (n = 40,  r = 0.9046)  obtained were linear and positive and the condition factor appeared to be the best predictor of fecundity in C. gariepinus studied.  The higher fecundity of C. gariepinus (range: 6,450 to 71,450) obtained from this study when compared with the range of 9,000 to 25,000 earlier reported from the wild stock indicates that hatchery-raised C. gariepinus is more fecund than the wild fish in the Anambra area of the sub-region.  Therefore, hatchery-raised C. gariepinus appears to be better for fish breeding in fingerlings production than the wild fish.