Patterns of sex ratio in the oil-sardine, Sardinella longiceps Val., at Calicut

Abstract

Categorising the fish according to maturity, montti of capture and length groups, the data on the sex distribution of the Indian oil-sardine (5flrrfwW/fl/ong'/fepj) collected at Calicut during 1959-60 to 1965-66 seasons are subjected to statistical tests to find outthe nature and cause of dominance of either sex, if any. For the immature fish the overall inference is that there may not be any significant difierences in the annual recruited population. In the adult fish the possibility of more males in May is suggested as due to the fact that the males may start maturing a little earlier than the females. The dominance of males in 140-150 mm group and that of females in 170-190 mm groups is brought about by differential growth, the females growing faster during June to October period. It is recommended that the size of each sample for sex ratio studies should be at least 50. Based on the earlier and the present studies of this author, It is indicated that 375 million ova can be expected from a tonne of adult biomass of the oil-sardine population.