Reproductive ecology of an invasive cichlid fish oreochromis mossambicus

Reproductive ecology of an invasive cichlid, Oreochromis mossambicus was studied using 654 specimens collected from Vembanad Lake, Kerala state. Females were predominant in the catches and the overall sex ratio was 1:1.40 (X²=17.83, p< 0.05), which significantly deviated from theoretical 1:1 distribution with 41.74% males and 58.26% females. Males and females in reproductive activity occurred throughout the year, the peak spawning period occurring between May to August and November to December. The length at which 50% (L ) of the fish were mature was 154.88 mm TL for males and 141.72 mm TL for females. The absolute fecundity ofO. mossambicus varied from 644-2210 eggs/fish with an average of 1469 and the relative fecundity ranged from10.12-19.23 eggs/g with an average of 15.54. Continuous spawning pattern, extreme parental care, fast sexual maturation, comparatively small eggs, predominance of females and tolerance to a wide range of environmental conditions promote the high recruitment of this invasive species in the lake and the adjoining rivers.