Seasonal dynamics and occurrences of three Dactylogyrus species on the gills of three cyprinids at Nwanedi–Luphephe dams in Limpopo province, South Africa

This study investigated the seasonal dynamics and occurrence of dactylogyrids on the gills of three cyprinids at Nwanedi–Luphephe dams from January to October 2008. The hosts, Labeobarbus marequensis (n = 53), Barbus trimaculatus (n = 63) and Barbus radiatus (n = 46), were collected using gill nets, cast nets, electrofishing gear and seine nets. A total of three Dactylogyrus species were found. Dactylogyrus spinicirrus was collected from all hosts, whereas Dactylogyrus afrolongicornis alberti and Dactylogyrus afrolongicornis afrolongicornis were collected from B. trimaculatus. Although D. spinicirrus was the most prevalent parasite on all three hosts, its mean intensity per host was found to be less than 10 individuals per host. Dactylogyrus afrolongicornis alberti and D. afrolongicornis afrolongicornis were less prevalent on the hosts, occurring in less than 50% of all hosts sampled, with a mean intensity of less than five individuals per host. The study showed that the intensity of D. spinicirrus infestation was influenced by season. Its occurrence displayed seasonal fluctuations with prevalence and mean intensity increasing with an increase in water temperatures. Other predictors of infestation such as fish sex and length did not have a significant influence on the prevalence and intensity of D. spinicirrus. Furthermore, parasite burdens did not have an effect on the condition of the host.Keywords: Barbus radiatus, Barbus trimaculatus, dactylogyrids, Labeobarbus marequensis, Limpopo River, Monogene