Occurrenceand distribution of fish parasites of potential threat to the acquaculture sector along the okavango river, Namibia
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Date
2015
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Abstract
Cichlids are subject to a wide range of diseases and parasites. Previously studies were conducted on fish parasites on the Okavango Delta, Botswana. This thesis is the first on fish parasites in the Kavango River, Namibia. The study aims to identify parasites occurring on commercially farmed fish i.e.: Oreochromis andersonii, Tilapia rendalli and Serranochromis robustus and to determine if these parasites
may have potential threat to aquaculture and humans. For the purpose of identification and calculating prevalence (pr) and abundance (ab) parasites
collected were fixed and stained using standard methods for each taxon. Kruskal-Wallis One Way Analysis of Variance was used to determine whether there were any significant differences in the number of fish parasites per zone, fish species and fish size. No significant differences were found in the number of parasites found in each zone, as well as the host fish species and group size of target fish species. A total of 205 specimens (91 T. rendalli, 89 O. andersonii and 25, S. robustus), were collected and examined for endo- and ectoparasites over twelve months. Of these 102 were infested with various parasites (total pr 49.7%), T. rendalli, 45%, O.
andersonii63% and S. robustus 13%. Parasites included Trichodina sp. (ab0.18) followed by Dactylogyrus sp. (ab0.17). Some Tripartiella and Epistylis spp. were collected in low levels as compared to other protozoan parasites. Helminths parasites such as Contracecum sp. were found in high abundance, whilst Proteocephalus, Clinostomum and Acanthocephala spp. were found in low abundance and infected mostly S. robustus. Opistolernaea (ab0.02) occurred in high numbers on T. rendalli and O. andersonii in zone 1 (Katwitwi to Kasivi). Dolops ranarum, Lernaea hardingi and Lamproglena monodi were also collected (ab0.02). Most of the infested fish species ranged from 1– 20.9 cm in total length, while the parasite Contracecum sp. was mostly found in fish ranging from 21 – 30.9 cm. Most of the infested fish were found in zones 3 (Mbambi to Popa Falls) and 4 (Popa Falls to Kwetze). This study could be a useful management tool for fisheries researchers in the aquaculture industry. In conclusion some protozoans and parasitic crustaceans, if found in high abundance, may cause a threat to aquaculture. Other parasites such as Contracecum sp. could be a concern to human health when fish is eaten raw, half cooked or inadequately smoked.
Description
A thesis submitted in fulfilment of the requirements for the Degree of Master of Science
Keywords
Fish parasites, Aquaculture, Kavango river, Distribution