A century of fish research in South African estuaries

Abstract

The history of South African estuarine ichthyology from 1910–2010 is reviewed. The first survey of fishes in a South African estuary was undertaken by Gilchrist in the early 1900s, followed by an extended period between the two world wars when little or no work was conducted in South African estuaries. In the 1940s and 1950s a series of surveys initiated by Day documented the fishes in a range of estuaries in KwaZulu-Natal and the Western Cape, but little detailed biological information was collected. The estuarine surveys of the 1950s and 1960s were superseded by autecological and synecological studies in the 1970s and 1980s which yielded descriptive and process-orientated information on a wide variety of fish species, including the larval stages of many taxa. This approach continued during the 1990s with publications dealing increasingly with the response of fish assemblages to declining freshwater inflows, the consequences of growing angling pressures on fish populations, and the increasing anthropogenic perturbations that necessitated the development of fish and estuarine health indices. In the late 1990s the impact of climate change on estuary-associated fishes became increasingly apparent and much research is currently focused around this topic. A number of projects have been activated at the subtropical/warm temperate and warm temperate/cool temperate transition zones in South Africa. However, baseline studies are urgently required to document changes in the tropical/subtropical transition zone in Mozambique and in the warm temperate/subtropical and subtropical/tropical zones in Angola so as to improve our understanding of the impact of climate change on estuary-associated fish species in Africa. Innovative methods, incorporating the use of biomarkers, otolith microchemistry, population genetics, acoustic telemetry, underwater videography and high-resolution sonic recordings, are opening up opportunities to test new hypotheses relating to estuarine fish ecology on the subcontinent.