Assessment of fish as bio-indicators of river health in rivers of the southwestern Cape

[摘要] ENGLISH ABSTRACT:In this study, the Fish Assemblage Integrity Index (FAll) was applied on three rivers within thesouthwestern Cape. This index uses fish as indicators of biological aquatic integrity and is based onindigenous species expected to be present in biological fish habitats. Fish integrity classes werecalculated for each of the sites in the three rivers studied. Sites 2 and 4 within the Lourens Riverwere rated as Class C, whereas sites 1 and 3 were rated as Class F and Class D respectively. Sites1, 2 and 4 within the Palmiet River were rated Class F, whereas sites 3 and 5 were rated as Class Eand Class D respectively. Site 1 within the Hout Bay River was rated as a Class F site, in addition tosites 2 and 3 been rated as Class A. It is however, suggested that the FAll needs to be adjusted toaccommodate the general low species richness experienced in the southwestern Cape. In addition tothe FAll been applied, the effects of long-term exposure to subtle water quality changes associatedwith human activities, specifically potential estrogenic compounds in fish from the Lourens Riverwere also investigated. The production of the yolk precursor lipoprotein complex, vitellogenin (Vtg)produced in the liver under estrogen control was employed as biomarker for environmental estrogenexposure. Male fish from the Lourens River were studied using SDS-PAGE gel electrophoresis.Results indicated that 60% of male fish showed the presence of Vtg in their plasma. Abnormalgonad morphology in male and female fish were also assessed using standard histologicalprocedures. Results from this study indicated no observed abnormalities in either male or femalegonads. The immediate presence of endocrine disrupters with estrogen activity was investigated byscreening water samples from the Lourens, Palmiet and Hout Bay Rivers for estrogen activity.Results indicated that none of the samples appeared to be cytotoxic. In addition, estrogen activity ofwater samples was also investigated by in vitro culturing of water samples with frog, Xenopuslaevis, liver slices. Results indicated that none of the water samples from the three rivers studiedindicated estrogenic activity. Although cytotoxicity and estrogen activity results were negative, theproduction of Vtg in male fish suggests further research regarding the presence of estrogenicsubstances in these rivers.

[发布机构] Stellenbosch University