Study of the structure and dynamics of demersal fish assemblages on the continental shelf and upper slop off Ghana, West Africa

Abstract

Using two-way indicator species analysis and detrended correspondence analysis, species on the continental shelf and upper slope of Ghana were classified into six assemblages. The structure of the assemblages is determined primarily by depth and type of sediment on the seabed. There are clear faunal discontinuities around 30-40 m, 100 m and 200 m depth. The dynamics of the assemblages are influenced by physico-chemical parameters of the water masses, mainly temperature, salinity and dissolved oxygen which are periodically modified by the seasonal coastal upwelling that occurs in the area. The observed changes in the composition and relative importance of species in the assemblages can be related to increased fishing activity and environmental forcing.