Relative condition factor and food and feeding of Jones' pony fish Eubleekeria jonesi (James, 1971) from Mandapam waters, Tamil Nadu, India

Abstract

The relative condition factor (Kn) based on length-weight relationship and food and feeding habits of Jones’ pony fish Eubleekeria jonesi (James, 1971) off Mandapam waters was studied during December 2016 - April 2018. The Kn values showed variations on a monthly basis with maximum value during September (1.23) for male and March (1.53) for female. Analysis of fullness of stomach of 961 samples within the size range of 51-130 mm revealed 40.87% fishes as actively fed, 36.19% as moderately fed and remaining 22.94% as poorly fed. The monthly mean fullness index (FI) was highest during September for both sexes. Highest gonadosomatic index (GSI), vacuity index (VI) and Kn value were observed during March-April in females, probably indicating a spawning peak and hence meagre feeding, which resulted in lowest fullness index (FI). Fishes of smallest length group (51-70 mm) had highest FI and minimum VI and vice versa. The values of index of relative importance (IRI) indicated that the species was planktivorous as well as detritivorous, with top priority towards crustaceans (27.6%) followed by bivalves (23.6%), foraminifera (15.4%), phytoplankton (12.5%), gastropods (9.1%) and nematodes (8.3%) in the gut contents. Diet did not show significant variation either sex-wise or size-wise.