Trophodynamics of the Spotfin Flathead Grammoplites suppositus (Troschel 1840) from the Southeast Arabian Sea

Abstract

The dietary habits of the spotfin flathead, Grammoplites suppositus which inhabits the southeast Arabian Sea was studied. The stomach contents of 581 specimens were analysed between September 2001 and May 2002. G. suppositus preyed primarily on crustaceans. The most important preys were benthic crabs and penaeid prawns, and fishes were next in rank. During premonsoon, fishes and crustaceans were equally important, whereas in monsoon and postmonsoon benthic crabs and penaeid prawns were the predominant prey. There were significant (p165 mm) ate crustaceans such as the benthic crabs, penaeid prawns, the paste shrimp, Acetes indicus and the mantis shrimp, Oratosquilla nepa. Highest similarity in diet was observed between 216- 240 and 241-265 mm length groups. Diet breadth was higher during the monsoon season; however, the trophic level which had a mean value of 3.79 ± 0.13 peaked during the postmonsoon season. Maximum diet breadth was for 191-215 mm length groups. The length of the prey Solenocera choprai had a linear positive correlation to the predator length (r2 = 0.72). Electivity studies showed that G. suppositus has a strong preference for low trophic level animals such as benthic crabs and Solenocera choprai. The Amundsen plot showed that G. suppositus is a specialized feeder on benthic crustaceans.