Occurrence And Distribution Of Fish Parasites Of Potential Threat To The Aquaculture Sector Along The Kavango River, Namibia

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.