Diets of abundant fishes from beach seine catches in seagrass beds of a tropical bay (Gazi Bay, Kenya)

Abstract

The composition of the diet of 14 fish species that were common in beach seine catches over the seagrass beds of Gazi Bay (Kenya) was investigated. Three trophic guilds could be distinguished based on dietary diversity and on the numerical and gravimetrical composition of the diet. Herklotsichthys quadrimaculatus, Stolephorus indicus and Atherinomorus duodecimalis were planktivores. Their stomach fullness index was low and the diet was not diverse. The main food items were harpacticoid and calanoid copepods and brachyuran zoea and megalopae. Apogon thermalis, Fowleria aurita, Paramonacanthus barnardi, Mulloides flavolineatus, Lutjanus fulviflamma, L. argentimaculatus and Gerres acinaces were benthivores, mainly feeding on small epi- and hyperbenthic prey. Their diet was very diverse and it was dominated by Amphipoda (Gammaridea), Tanaidacea and Mysidacea. Their fullness indices were low, but a little bit higher than those observed for the planktivores. A third group were the 'piscivores': Bothus myriaster, Fistularia commersonii, Sphyraena barracuda and Plotosus lineatus . The dominant items in the food spectrum of these species were postlarval fishes and large nektonic invertebrates (gammaridean amphipods, mysids, shrimp and crabs). Their diet was not diverse and the fullness index was much higher than that of the other species examined. All other species caught were further classified according to the following feeding guilds: herbivores, planktivores, benthivores (epi- and hyperbenthivores) and piscivores. The ichthyofauna of Gazi Bay was clearly dominated by benthivores.