FISH HEALTH AND PARASITES
4.4 CONCLUSIONS
Health Assessment Index and Parasite Index
In terms of HAI, both fish species recorded a mean population values ranging from 17 to 51 which indicated to be an intermediate impacted site. The Health Assessment Index (HAI) values of the two fish species differed significantly with higher values recorded for C. gariepinus than L. rosae. Higher HAI values were recorded for L. rosae than C.
gariepinus during winter, spring and summer which are an indication that L. rosae was more affected by parasites. The highest population mean HAI value was recorded in summer for both fish species and the lowest HAI value was recorded in autumn for both fish species. The Endo-PI was higher than Ecto-PI for C. gariepinus. The opposite was observed for L. rosae in which the Ecto-PI was higher than the Endo-PI in all seasons except summer. No abnormalities in fins, kidneys, opercules, hindgut, mesentery fat, bile and spleens were observed during the study.
All the fish at the barrage appear to be healthy, with no visible abnormalities except a few fishes (n=25) which showed mild skin aberration, discolorations on the liver, below and above normal haematocrit values of some fish (mostly in C. gariepinus). Eyes, skin, fins and opercula were found to be normal for both fish species at the Phalaborwa Barrage, the liver condition and haematocrit values contributed mostly to the HAI values. Liver discoloration, HCT values, and parasites contributed to higher HAI values in C.
gariepinus. The haematocrit values were one of the most affected variables, showing differences among species.
A greater number of parasites were recorded in C. gariepinus than L. rosae however; C.
gariepinus exhibited a higher number of endoparasites than ectoparasites while L. rosae exhibited a higher number of ectoparasites than endoparasites. High numbers of endoparasites from C. gariepinus was due to high number of nematodes while higher number of ectoparasites in L. rosae was mainly due to the monogenean group of parasites. It can therefore be concluded that ectoparasites in L. rosae contributed to the elevated HAI value.
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High numbers of ectoparasites were recorded in L. rosae than in C. gariepinus while higher numbers of endoparasites were recorded in C. gariepinus than L. rosae. The dominating ectoparasites for both species were from the class monogenea. Although the prevalence for Contracaecum sp. in C. gariepinus was 100% in all seasons, it did not influence the condition of the host. The parasites identified from both fish species neither reached alarmingly infection levels nor caused any visible damage to the host. One digenean parasite (Nematobothrium sp.) found in the orbit of L. rosae is a new record for South Africa (and possibly a new species) which was first identified at the Flag Boshielo Dam. Fish health (including parasite burden) is important as freshwater fish is consumed (especially in rural areas) by humans on a regular basis. The digenean larvae, including Clinostomum and the digenean cysts were observed from the gills and the muscle.
The highest prevalence was recorded in L. rosae for the ectoparasites group. The highest prevalence for ectoparasites collected from L. rosae was in spring and summer while the lowest prevalence was recorded in winter for Dactylogrus pienaari. In C. gariepinus, the highest prevalence recorded for ectoparasites was in winter for Lamproglena clariae while the lowest prevalence was recorded in summer for Quadriacanthus aegypticus. The highest mean intensities for ectoparasites in C. gariepinus were recorded in summer for Quadriacanthus aegypticus and Macrogyrodactylus clarii and lowest in autumn for Lamproglena clariae. The highest mean intensity for ectoparasites for L. rosae was recorded in winter for Dactylogrus pienaari and lowest in autumn for Dogielus sp.
Higher numbers for C. gariepinus were recorded in winter for Lamproglena clariae and low numbers of ecto-parasites were recorded in spring for Quadriacanthus aegypticus.
For L. rosae highest numbers of ectoparasites were recorded in summer and low numbers of ectoparasites were recorded in winter for Dactylogrus pienaari. Highest number of ectoparasites in C. gariepinus and L. rosae were recorded in winter and summer, while the lowest number of parasites was recorded in spring and winter respectively.
For endoparasites, both fish species exhibited a slight different seasonal trends compared to those observed for ectoparasites and as well as compared between species. The lowest prevalence of endoparasites for C. gariepinus was recorded in spring for
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Glossidium pedatum and larval cestodes in all seasons and the highest prevalence was recorded in all seasons for Contracaecum sp. The highest prevalence for L. rosae for endoparasites was recorded during autumn for Nematobothrium sp and lowest during winter and summer for Nematobothrium sp.
The same trend for mean intensity of endoparasites was observed for both fish species.
The highest mean abundance of endoparasites in C. gariepinus was recorded during autumn. For L. rosae, the lowest endoparasites mean abundance was recorded in summer and autumn for Nematobothrium sp. The highest mean intensity value for endoparasites in C. gariepinus was recorded during autumn. For L. rosae, mean intensities for endoparasites ranged from 1.8 to 10 for Nematobothrium sp in autumn and summer respectively.
Condition Factor
When comparing the two fish species, L. rosae had slightly higher condition factor values in all seasons than C. gariepinus which also correlated with the HAI values calculated for each fish species. The condition or wellness of L. rosae was also better than that of C.
gariepinus during all seasons. Furthermore, the condition factor findings correlate with the HAI values of both fish species whereby C. gariepinus had highest parasite numbers and highest HAI values, of which both might have impacted on the overall condition of its health as compared to L. rosae. Labeo rosae showed opposite results to C. gariepinus;
less ectoparasites, lower HAI values and condition factor.
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