The trophodynamics and reproductive biology of koth Otolithoides biauritus caught by trawlers at Vanakbara, Diu was studied for the period from September 2005 to May 2008. The length-weight relationship showed that growth was allometric and there was no significant difference between the sexes. The overall sex ratio was 1:1.09 with mature females occurring throughout the year. The peak breeding season was in the monsoon season from May to August as evidenced by maturity stages, gonado-somatic index and the size progression of yolked ova. The length at first maturity of the female was 110.15 cm. The absolute fecundity ranged from 1,82,020 to 1,941,400. The mature ovaries of O. biauritus contained two batches of mature ova measuring from 0.75 to 0.79 mm and 0.65 to 0.69 mm in diameter. O. biauritus was found to feed more intensely during the post-monsoon months. The most important food item was Acetes spp. followed by finfishes. Fishes possessing empty stomachs were frequently encountered in the commercial catch. Young ones of O. biauritus fed more abundantly than adults with penaeid prawns dominating the gut contents while adults preferred finfishes as their diet.