Masters Degrees (DFOS)

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Browsing Masters Degrees (DFOS) by Subject "Aquaculture"

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    Effect of pawpaw (Carica Papaya) seed meal on growth performance, feed utilization, survival and masculinization of sexualy undifferentiated three spotted Tilapia (Oreochromis Andersonii) fry
    (University of Namibia, 2019) Iipinge, Linda Nuushona
    The objective of this study was to determine the effects of dietary Carica papaya seed meal supplementation at different levels on growth performance, feed utilization, survival rate and sex ratio of sexually undifferentiated three spotted tilapia (Oreochromis andersonii) fry. Six treatments (replicated thrice) were designed based on the control (basal diet), 17 α-methyltestosterone (MT) (60 mg) and C. papaya seed meal incorporated into tilapia feed at 5, 15, 25 and 35 g / kg diet and administered to freshly hatched fry (9 days old) for 120 days. The swim up fry (initial body weight 0.04 g / fry) were collected from the aquarium and randomly distributed (𝑛=80) at each of eighteen black bins with a holding capacity of 200 L. The results showed that the growth performance of the fish fed varying inclusion levels of pawpaw seed meal did not differ significantly from those fed basal diet and 60 mg of MT. A decrease in growth performance and poor feed utilization capacity was observed in the treated fish with increasing dietary C. papaya inclusion levels from 15 g / kg to 35 g / kg diet, suggesting that it had inhibited the growth at high dosage. Pawpaw seed meal was able to skew the sex ratio in favour of males, from the expected ratio of 1:1 male: female for all the treatments. The percentage of males increased for the treatments with increasing the dietary inclusion level, with the highest masculinization percentage (82%) (P < 0.05) observed in fish fed with 15 g and 35 g of C. papaya extracts / kg diet. Dietary C. papaya did not significantly change the fish survival rate among the treatments (P > 0.05), signifying that it had no lethal effect. This study showed the possibility of using pawpaw seed meal as a natural agent to induce sex reversal in three spotted tilapia. Due to the safety, ease of biodegradation and local availability of this naturally sourced sex reversal agent, the study recommends that, it could be used as a viable alternative to popular synthetic hormones. In order to improve growth and induce sex reversal at the same time, the study recommends the use of 5 g but not ≥ 15 g C. papaya extracts / kg diet to be economically viable and efficient for fish farms.
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    Occurrenceand distribution of fish parasites of potential threat to the acquaculture sector along the okavango river, Namibia
    (2015) Mumba, Victoria
    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.