A Study on nematode infestation in fish found in the Hardap Dam, Namibia

Abstract

ix List of Appendices Appendix 1: Larvae of Contracaecum sp. found in different sites in the fishes .......................... 35 Appendix 2: Species composition based on males, females and the unknown of gillnet catches (multifilament, 12-150m) from Hardap dam August – October 2012. ......................................... 36 Appendix 3: Species composition of gillnet catches (multifilament, 12-150m) from Hardap dam August – October 2012. ................................................................................................................ 37 Appendix 4: Data collection forms .............................................................................................. 38 Appendix 5: Raw data of the fish sampled from Hardap dam using gill nets during August – October 2012…………………………………………………………………………………………………………………………..39 Appendix 6: Illustration of the sampling and study and procedures undertaken for the study……………………………………………………………………………………………………………………………………….40 x ABSTRACT This study was conducted to investigate the abundance of nematode infestation in several fish species found in the Hardap Dam. The under taken study aimed at identifying the fish parasite (nematode) found in the fishes of the Hardap Dam and illustrate its correlation between the fish species, sizes, within and between the species as well between the sexes in each species.A total of 2951 fishes belonging to six different species were collectedin August and October 2012. These species included; Cyprinus carpio (Common carp), Barbus paludinosus (Straight-fin barb), Labeobarbus aenus x Labeobarbus kimberleyensis (Yellow-fish hybrid), Labeo umbratus x L. capensis (Labeo mudfish-hybrid), Clarias gariepinus (African Sharp-tooth catfish) and 0reochromismossambicus (Tilapia).Of the 2952 specimens collected, 2.6% were infected with the nematode parasite. The nematode parasite was identified as the Contracaecum species. Clarias gariepinus, Oreochromis mossambicus andYellow-fish hybridwere found to be more prone and Labeo mudfish-hybridthe least infested with the nematode. The intensity of the infection was 1-73 worms per fish in yellow-fish hybrid, 0-19 worms per fish in the Tilapia fish, 22 -832 worms per fish in Clarias gariepinusand 0-2 worms in the Labeo mudfish-hybrid. Species variation in the prevalence of parasite was observed with no significant difference in the prevalence of infection between males and females. Body length was positively correlated with the number of parasites in the yellow fish hybrid (r2=0.3713; P<0.0001).