The ichthyofauna of a tropical mangrove bay (Gazi Bay, Kenya): community structure and trophic organisation

Abstract

The spatial and temporal community structure and the trophic organization of the fish fauna in Gazi Bay (Kenya) are discussed. Gazi bay is presented as part of the entire Eastern African coastal area subjected to the oceanographic and atmospheric processes in the Western Indian Ocean region (WIO). The aim of this study was to collate and synthesise the available information, to collect a time series of new, quantitative data on the fish fauna of Gazi Bay and also to attempt to identify observable patterns in relation to the biotic and abiotic environment of the bay. In total, 346 species in 72 families of fish have been reported from Gazi bay. Of these, only 11 species and 20 families were common to all the six campaigns. A total of 180 species and 20 families were unique to one or the other campaign. It was characteristic of all the campaigns that very few species dominated the catch, the majority of species representing <0.05 % each, of the total number of individuals caught. Sphaeramia orbicularis, constituted 96 % of the total catch in fykenets and dragnets deployed in the mangrove swamp. Atherinomorus duodecimalis, A. lacunosus, Herklotsichthys quadrimaculatus and Gerres acinaces were the most abundant species caught in beach seines, where only 3 species made up to 70 % of the total catch per campaign. The dominant species in beam trawls were Leptoscarus vaigiensis, Scarus sordidus, Plotosus lineatus, Parascorpaena mossambica, Sebastapistes strongia, Apogon fragilis, A. nigripes, Fowleria aurita, Siganus sutor, Lethrinus harak, L. nebulosus and Cheilia. This work is a major contribution to the understanding of the fish ecology and the diversity of the fish fauna in an intimately placed tropical coastal ecosystem.