Natural diet of the alligator pipefish, Syngnathoides biaculeatus (Bloch, 1785) inhabiting Palk Bay, southeast coast of India

Abstract

A total of 56 guts of the alligator pipefish, Syngnathoides biaculeatus collected from Palk Bay, southeast coast of India were analysed for determining its natural diet composition. The gut fullness index as assessed by point method showed that the majority of fish (71.43%) either had half-full (37.5%) or quarter-full guts (33.93%). Mean values of relative growth length (RGL) and gonado-somatic index (GSI) were estimated to be 0.36�0.03 and 3.78�1.67%, respectively. Copepods and sand particles occurred with 100% frequency of occurrence (%FO) followed by amphipods (%FO=99.25) isopods (%FO=86.79), peracarids (%FO=70.76) and decapods (%FO=65.28). The results of the gut content analysis showed that S. biaculeatus largely preyed on crustaceans (~90%) which included amphipods (40.36%), copepods (35.27%), decapods (8.12%), isopods (3.48%) and peracarids (2.21%). Consistent occurrence of sand particles and algal pieces in the guts reflect the feeding behaviour of S. biaculeatus in seagrass habitat over the sandy bottom. No significance difference in prey numbers and composition between male and female specimens was observed (P>0.05).