Nutritional condition of fish larvae in South African estuaries: an appraisal of three biochemical methods

  • D Costalago
  • N Strydom
  • C Frost

Abstract

Estuaries are exposed to a number of threats and many South African estuarine systems are functionally and structurally altered. The extent to which fish are affected by these alterations is not fully understood. The estuarine round herring Gilchristella aestuaria is an appropriate species to use when examining such effects. The most widely used approaches to evaluating the nutritional condition of fish larvae are based on biochemical methods. In order to identify the most suitable technique for assessing body condition of fish larvae in estuaries, the nutritional condition of post-flexion larvae of G. aestuaria from the Sundays and Kariega estuaries on the south-east coast of South Africa was evaluated using three different biochemical techniques: (i) total lipid content analysis and the triacylglycerol/cholesterol (TAG/CHOL) ratio; (ii) protein content analysis; and (iii) the RNA/DNA ratio. Results from techniques (ii) and (iii) revealed that G. aestuaria larvae from the Kariega Estuary were in better condition than larvae from the Sundays Estuary, probably due to a recent plankton bloom. It is concluded that the individual RNA/DNA ratio can provide a reliable, sensitive and cost-effective method to assess the immediate effects of environmental changes on the nutritional condition of estuarine fish larvae.

Keywords: estuarine ecology, Gilchristella aestuaria larvae, lipid content, protein content, RNA/DNA ratio, round herring

African Journal of Marine Science 2014, 36(3): 377–386

Author Biographies

D Costalago
Department of Zoology, Nelson Mandela Metropolitan University, Port Elizabeth, South Africa
N Strydom
Department of Zoology, Nelson Mandela Metropolitan University, Port Elizabeth, South Africa
C Frost
Department of Biochemistry and Microbiology, Nelson Mandela Metropolitan University, Port Elizabeth, South Africa
Published
2014-11-04
Section
Articles

Journal Identifiers


eISSN: 1814-2338
print ISSN: 1814-232X