Description of larval fish composition, abundance and distribution in nine south and west coast estuaries of South Africa

Abstract

The composition, abundance and distribution of larval fishes from nine south and west coast estuaries from South Africa was investigated by plankton tow once per season between June 2003 and March 2004. A total of 49 274 early stage fishes were caught, comprising nine orders, 20 families, 29 genera and 47 taxa. Seven species accounted for 93.4% of the total catch in these estuaries, namely Gilchristella aestuaria (78.8%), Caffrogobius gilchristi (6.2%), Psammogobius knysnaensis (3.5%), C. nudiceps (2.5%), Parablennius sp. (2.4%), Omobranchus woodi (2.1%) and Atherina breviceps (1.9%). The majority (70%) of identified species are endemic to southern Africa and 96.4% of the larvae caught were estuary-resident species. Larval fish assemblages in the sampled estuaries exhibited the same seasonal and spatial patterns described for temperate estuaries both in South Africa and worldwide. Larval fish were more abundant in summer and in the mesohaline zone. The assemblages were less diverse and dominated by fewer species than temperate estuaries along the south east coast of South Africa. The differences found in composition and density of the larval fish assemblages from south and west coast estuaries result from the biogeography of the area and the differences in freshwater inflow.

Keywords: ichthyoplankton, cool-temperate, community structure, biogeography, estuary type.