The results of studies on the biological aspects such as sexuality, sex ratio, size at first maturity, spawning, age and growth, distribution of adults, food, predators,Iife-history and distribution of juveniles of three species of squids Loligo duvaucelii, Sephreuthis lessoniana and Doryteuthis sibogae are presented. The breeding period of all the three species was found to be prolonged. In Lotigo duvaucelii the males attained sexual maturity earlier than females in the various fishing grounds investigated
