Food habit and diet composition of Karalla dussumieri (Valenciennes, 1835) and Gazza minuta (Bloch, 1795) from Mandapam vicinity of Gulf of Mannar, Tamil Nadu

Abstract

The diet composition and food habits of two species of Silverbellies, Karalla dussumieri (Valenciennes, 1835) and Gazza minuta (Bloch, 1795) from Mandapam vicinity of Gulf of Mannar was analysed. The diet composition was studied from December 2016 to April 2018. K. dussumieri with full stomachs appeared in very high percentages (100%) in December followed by empty stomachs (100%) in January and February. Empty stomachs were prevalent in most of the months for G. minuta with a peak in January (100%). The vacuity index (VI) of K. dussumieri was highest during January (100%) and minimum from September to December (11-21%). Correspondingly the highest fullness index (FI) was recorded during December (4.69). The monthly mean FI of G. minuta has shown a single maximum value during August (4.81), whereas the highest VI was noticed in most of the months with a peak in January (100%). Fishes of higher length group 105-110 mm and above had the highest FI in both species. The diet analysis of K. dussumieri revealed that a planktivorous feeding habit as copepods became the principal diet with an average %IRI of 32%, followed by foraminifera (26.12%). The monthly average %IRI values showed that G. minuta is a carnivorous fish with teleost fishes (50%) as the main food followed by shrimps (15%) and copepods (9%). The gut content of smaller fishes showed diatoms, polychaetes and amphipods as the main components and as they grew, more of nekton appeared in the stomach.