A preliminary fish survey of the estuaries on the southeast coast of South Africa, Kayser’s Beach – Kei Mouth: a comparative study

Td Harrison,Nc James

doi:10.4314/wsa.v42i1.10

Abstract

A basic ichthyofaunal and physico-chemical survey of estuaries on the southeast coast of South Africa from Kayser’s Beach to Kei Mouth was undertaken during September and October 1996. Twenty-eight (28) estuaries have been identified along this stretch of coastline, and these were grouped into three types: small ( 10 ha) predominantly closed estuaries, and predominantly open estuaries. Multivariate analyses revealed significant differences between estuarine types both in terms of their physico-chemical characteristics and fish communities. These features were consistent with those reported in other parts of the south and southeast coast. Overall, predominantly closed estuaries had a lower species diversity than predominantly open estuaries and smaller systems had a lower species diversity than moderate to large systems. Although differences were observed between estuarine types, most systems provided important habitat for a number of estuarine-dependent marine species as well as resident species, which were often recorded in high numbers. Many of these species were also endemic, which further emphasises the importance of these estuaries in maintaining ichthyofaunal diversity in the region. This survey represents one of the few fish surveys undertaken along this little-studied section of coastline. Keywords: ichthyofauna, estuarine survey, fish habitat, southeast coast

Highlights

Warm-temperate estuaries constitute important nursery areas for a number of estuarine-associated fish species (e.g. Potter and Hyndes, 1999; James et al, 2007a)
The Hlozi and Hlaze estuaries exhibited a horizontal decrease in salinity of more than 1.0, while a marked vertical salinity gradient was only evident in the Cunge and Cwili estuaries
Mean turbidity values ranged from 3.5 NTU (Hlozi and Hlaze) to 36.2 NTU (Cwili); relatively high (>33 NTU) average turbidities were recorded in the Haga-Haga, Mtendwe and Cwili systems, a result of heavy rainfall in their catchments

Summary

Introduction

Warm-temperate estuaries constitute important nursery areas for a number of estuarine-associated fish species (e.g. Potter and Hyndes, 1999; James et al, 2007a). In order to understand change in estuaries and maintain their ecological function, basic information is needed on fish assemblages. This information is often lacking, for estuaries on the southeast coast of South Africa, around East London. Studies have been carried out on the biology of the Nahoon (Steinke, 1986; Campbell et al, 2001; Bursey and Wooldridge, 2002; 2003; Sale, 2007; Geldenhuys, 2013), Nyara (Perisinotto et al, 2000, Walker et al, 2001), Goda (Vumazonke et al, 2008) and Haga Haga (Whitfield, 1992) estuaries, no information exists on fish biodiversity for the majority of systems along this coastline. As part of a national assessment of South African estuaries, a fish survey was undertaken along the southeast coastline between Kayser’s Beach and Kei Mouth; basic physico-chemical variables, fish community data and a comparative analysis are provided

Methods

Results

Conclusion