Reproductive Biology of Commercially Valuable Squid, Sepioteuthis lessoniana (Lesson, 1830) Taken as By-Catch in a Tropical Trawl Fishery

Some aspects of the reproductive characteristics of the commercially important squid Sepioteuthis lessoniana (Lesson, 1830) in the coastal waters of Mandapam, Palk Bay was studied with a view to provide possible management measures in this region. A total of 984 individuals (508 males and 476 females) were collected between April, 2009 to March, 2010. The size of specimens ranged from 40 mm to 290 mm in mantle length. Sex ratio was not significantly different from the expected ratio of 1:1 except for months of July, October and December. Spawning season as revealed by seasonal maturity stages, gonadosomatic index of sexes and nidamental gland length (NGL) and dorsal mantle length (DML) ratio of females, lied between January to June with peak at February. Size at maturity as determined by graphical method was 83.5 for males and 112.5 for females.