Sperm motility and testicular histology as reproductive indicators in Clarias gariepinus from an eutrophic impoundment, South Africa

Testicular histology and sperm motility were studied as possible reproductive indicators of the reproductive potential for the wild, indigenous fish species (Clarias gariepinus) from an eutrophic impoundment, the Hartbeespoort Dam (HD) in South Africa. Parameters used as indicators include: GSI, testes histology and staging of the testes. Computer assisted sperm analysis (CASA), was used to assess sperm motility parameters including percent motile sperm (% MOT), velocity curvilinear (VCL mu m s(-1)) and progression (PROG). These parameters were compared to C. gariepinus sampled at a reference site, the Marico Bosveld dam (MD). Water samples from both dams were analysed for metals and selected endocrine disrupting chemicals (EDCs). The water samples in the HD had notable high levels of selenium as well as nonylphenol and Di-n-Butyl phthalate. Macroscopic differences in the testes were found comparing the HD and MD. Fish from HD testes showed abnormalities regarding the interstitial tissue possibly due to proliferation of connective tissue. The CASA results showed no significant (P >= 0.05) differences for the% MOT of fish spermatozoa between HD and MD. The VCL and PROG of sperm had significant (P < 0.05) differences in fish between HD-LF, HD-HF and MD. It here fore seems that the increased environmental pollutants in the HD had an effect on reproductive status and sperm motility parameters of C. gariepinus when compared to the reference site MD.