Diet of selected fish species in the freshwater-deprived St Lucia Estuary, South Africa, assessed using stable isotopes
2012; Taylor & Francis; Volume: 8; Issue: 8 Linguagem: Inglês
10.1080/17451000.2012.678855
ISSN1745-1019
AutoresNicola K. Carrasco, Renzo Perissinotto, Holly Nel,
Tópico(s)Aquatic Ecosystems and Biodiversity
ResumoAbstract Abstract The St Lucia Estuary, Africa's largest estuarine lake, is the most important juvenile fish nursery on the south-east African coastline and is currently experiencing an unprecedented crisis. Prolonged freshwater deprivation has resulted in hypersaline conditions in the northern regions of the lake, as well as low water levels. The mixed model SIAR (Stable Isotope Analysis in R) was used to determine the likely contribution of each of the available carbon sources to the diets of selected fish species. This was complemented with ad-hoc gut content analysis of representative specimens. Two diverse regions of the lake system were investigated: Charters Creek, which has been severely affected by the desiccation process, and the Mouth, which is somewhat protected due to the freshwater input from the Mfolozi and Mpate rivers. The mysid Mesopodopsis africana was found to be important in the diet of a number of fish species, namely, Leiognathus equula, Ambassis ambassis and Gerres acinaces. The copepod Pseudodiaptomus stuhlmanni and the mysid Rhopalophthalmus tropicalis were most important in the diet of Gilchristella aestuaria. Mozambique tilapia (Oreochromis mossambicus) exhibited the most variable diet, the flexibility of which may aid survival during harsh conditions and could explain its current dominance throughout the system. Keywords: Droughtfish dietiSimangaliso Wetland Parkstable isotopesgut content analysis Acknowledgements Sincere thanks go to the iSimangaliso Wetlands Park Authority and the staff and management of EKZN Wildlife. Special mention must be made of Ricky Taylor and Caroline Fox for their support throughout this study. Shivanee Pillay, Garrett Kruger and Nelson Miranda are gratefully acknowledged for their help in the field. Funding for this project was provided by the National Research Foundation (NRF, Pretoria), Marine and Coastal Management (DEA-MCM, Cape Town) and the World Wide Fund (WWF).
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