Observations on some aspects of biology of Alepes djedaba (Forsskal) from Cochin

Abstract

This paper includes observations made on the food, feeding habits, breeding biology, length weight relationship and relative condition factor of Alepes djedaba for the period 1986-87. The fish feeds mainly on young fishes (Stolephorus spp., Cynoglossus spp., Leiognathus spp.), crustaceans like decapods (Aceles spp., Lucifer spp.), ostrocods (Conchaecia spp.), amphipods and cladocerans (Evadna spp.) followed by nematodes, insect body parts and insect larvae. Higher percentage occurrence of empty stomachs and lower volume of food consumed during breeding season is indicative of reduced feeding activity during that period. Fish within a length range of lSO-199 mm and 240-319 mm showed a preference for young fishes, while those in the length range of 200-239 mm relished for ostra- . cods and other crustacians. The ova diameter studies indicated presence of batches of ova mature and maturing probably releasing in two batches during June to November. There is no significant difference in the lengthweight regression coefficient in the two sexes. Hence, the length-weight relationship for both the sexes together is calculated : Log W - —5.308528 + 3.146849 Log. L. The size at first maturity in females is found to be 180-189 mm. Sex ratio showed predominance of males in most months.