Dietary preference and feeding ecology of bloch's gizzard shad, Nematalosa nasus

Abstract

Dietary preference and feeding ecology of Nematalosa nasus (Bloch 1795) in Chilika lagoon, India, was investigated through analysis of prey items in the guts and that in the habitat. Of the 230 taxa identified from the habitat in plankton samples from the lagoon, thirty five taxa were recorded from the guts of the fish. Index of Relative Importance showed 80% of the food comprised of microplankton groups viz. Foraminifera (35.79%), Chlorophyceae (20.52%), Bacillariophyaceae (12.30%), Cyanophyaceae (6.53%), other plant matter (3.65%) and Euglenophyaceae (0.76%). The fish is a generalized feeder on microplankton, with specialization on foraminiferans and Chlorophyaceae in Chilika Lagoon. Diet composition varied significantly with seasons. Prey type selectivity showed, preference to Gyrosigma sp. (αi—0.98, ei—0.85), Synedra sp. (αi—0.47, ei—0.71), Tabellaria sp. (αi—0.58, ei—0.47) and Ulothrix sp. (αi—0.06, ei—0.34) during monsoon and post-monsoonseason. Ammoniabeccarii (αi—0.77 ei—0.98), Campylodiscus sp. (αi—0.04, ei—0.17) and Microspora sp. (αi—0.18, ei—0.76), were selected during pre-monsoon period, which is also the peak breeding period of the fish.