Trophic spectrum of Pseudotolithus elongatus (Sciaenidae: Teleostei) in Imo River estuary, Nigeria

Abstract

The trophic spectrum of Pseudotolithus elongatus in Imo River Estuary was studied using the index of relative importance (IRI).This index combines three standard methods of stomach analysis namely: the point, frequency of occurrence and numerical methods. The resultant IRI was further expressed as a percentage for each food item. The major dietary categories were of two classes namely: crustacean (shrimps) and Pisces (fish) with % IRI of 51.81% and 24.34% respectively. Other items (unidentified mass of tissues, plant materials, and polychaete worms) had a total % IRI of 23.84%. The food composition showed no variation with sex and season except for the presence of plant materials occurring only in the raining season. Feeding intensity was greater in the dry than in the wet season and in females than in males. The largest size group (41-50 cm) exhibited the highest intensity of feeding but no clear ontogenic pattern in vacuity index was observed.