Breeding season, maturation, fecundity and condition factor of African catfish Clarias gariepinus Burchell 1822 (Pisces: Clariidae) in Lake Chamo, Ethiopia

Abstract

Some aspects of reproductive biology, length-weight relationship and condition factor of Clarias gariepinus (Burchell) were studied from January - December 1999 in an Ethiopian rift-valley lake (Lake Chamo). Except in some months and size classes, sex ratios didn’t differ significantly from 1:1, with season and size class. Males were more numerous than females in 20.0- 29.9 cm, 60.0-69.9 cm and >90 cm size classes (x= 4.50, p<0.05; x² = 3.88, p<0.05; x² = 16.00, P < 0.001, respectively). Significantly more males than females were also caught in January (x² = 4.46, p<0.01), March (x² = 10.79, p<0.01) and October (x² = 10.45, p<0.01). C. gariepinus spawned over an extended period, and the main pulse in reproductive activity occurred during the rainy months of March - June. Length at first maturity (L_m50) of females was 58 cm while L_m50 of the males was 52 cm. Fecundity ranged from 5,000 -1,240,000 eggs with the mean at 337,700. Ripe ovaries contained 625 - 2,760 eggs g^-1 of wet weight with the mean of 1,110 eggs. The relationships between total length and fecundity, and total weight and fecundity were curvilinear while the relationship between ovary weight and fecundity was linear. Length-weight relationship for C. gariepinus is best expressed by the equation TW = 0.0035TL^3.19. Mean monthly Clark’s condition factor of the females ranged from 0.274 ± 0.036 - 0.350 ± 0.030 while that of males ranged from 0.278 ± 0.02 - 0.343 ± 0.028.

Keywords/phrases: Clarias gariepinus, Condition factor, Lake Chamo, Reproduction

Ethiop. J. Biol. Sci. 10(1): 1-17, 2011