Trophic Ecology of Some Common Juvenile Fish Species in Mtwapa Creek, Kenya

Abstract

The trophic status of common fish species in Mtwapa creek on the Kenyan coast was studied. Both the qualitative and quantitative spectra of the diets of these fish species were investigated. It was found that the eight most abundant fish species, Sardinella gibbosa, Pellona ditchella, Spratelloides delicatilus, Atherinomorous lacunosus, Gerres oyena, Secutor insidiator and Leiognathus equula , consumed principally copepods, while Selar crumenophthalmus fed mainly on fish scales. Polychaetes were an important diet for Gerres oyena and Leiognathus equula . Spratelloides delicatilus was a carnivore feeding only on zooplankton and zoobenthos, and had the lowest diet diversity (H' = 0.40). The rest were omnivorous. Sardinella gibbosa, P. ditchella, L. equula, Sec. insidiator, G. oyena and Sel. crumenophthalmus fed on phytoplankton, zooplankton, zoobenthos and detritus with a relatively higher diet diversity (H' = 0.68–0.96). Atherinomorous lacunosus did not take detritus in its diet and it had a lower diet diversity compared to the other omnivores (H' = 0.47). The feeding niches of the examined species were highly overlapped. The Morisita feeding niche overlap values ranged between 0.84 and 1.00. Most of them were generalized opportunistic feeders except for S. dilicatilus, which exhibited a specialised feeding strategy. Overall, this study showed that the fishes had a flexible diet, which relied greatly on the prevailing biotic and abiotic conditions in their habitats. Keywords : trophic ecology, fish, Mtwapa, Kenya West Indian Ocean Journal of Marine Science Vol. 3 (2) 2004: pp. 179-188