Ecto-and endo- parasites of silver kob (Argyrosomus Inodorus) from northern Namibia (21º 24ºS) select="/dri:document/dri:meta/dri:pageMeta/dri:metadata[@element='title']/node()"/>

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Show simple item record Amakali, Annette Megameno 2019-06-10T14:01:25Z 2019-06-10T14:01:25Z 2019
dc.description A research thesis submitted in fulfillment of the requirements for the Degree of Master of Science in Fisheries and Aquatic Science en_US
dc.description.abstract The silver kob (Argyrosomus inodorus) has been identified as a candidate species for finfish culture due to its outstanding qualities. There is little information available on the health of this species, especially parasite infestation that can pose a threat to fish cultivation and therefore to the success of mariculture. This study was thus designed to provide information on parasites that are affecting this species. Silver kob were collected monthly (2017–2018 for 11 months) using conventional fishing gear (n = 55) in Toscanini, Mile 108 and Henties Bay, northern Namibia (21° - 24°S). Fish were examined for ecto- and endo-parasites. Drawings and measurements of parasites were made using a camera lucida and calibrated eyepiece of an Olympus BX50 binocular microscope and/or a Zeiss (Discovery V8) camera calibrated on a Leica dissecting microscope. Parasite organ specificity was determined. Parasite prevalence, mean intensity and mean abundance were analysed by season of capture, fish length and fish sex. Chi-square tests were used to determine differences in mean abundance by season, host sex and host length. Twenty-eight species from 17 parasite genera were found, including monogeneans (five Diplectanum spp., Sinodiplectanotrema sp., four Calceostoma spp., Neocalceosoma sp. and Sciaenacotyle sp.), digeneans (Helicometra sp., three Helicometrina sp., and Stephanostomum sp.), cestode larvae (Callitetrarhynchus sp., a Tetraphyllidean plerocercoid), a nematode (Anisakis sp.), a palaeacanthocephalan (Corynosoma australe), copepods (Caligus sp., Sciaenophilus sp., Lernanthropus sp., two Brachiella spp.) and an unknown parasite. More ecto-parasites were organ specific than endo-parasites. Corynosoma australe and Calceostoma spp. were significantly more abundant during the cold season (June-November) (X2 = 31.56, p <0.001 and X2 = 3.10, p value = 0.048, respectively), and Diplectanum spp. were significantly more abundant during the warm season (December-May) (X2 = 24.44, p <0.001). With the exception of digeneans, larger sized fish (TL > 47.3 cm) showed the highest prevalence and mean abundance of parasites compared to smaller sized fish (TL ≤ 35.8 cm). Calceostoma spp. and Helicometrina spp. showed a significant decrease in mean abundance with increasing host length (X2 = 28.22, p <0.01 and X2 = 5.77, p = 0.03, respectively). Corynosoma australe and Diplectanum spp. showed a significant increase (X2 = 20.2, p <0.01 and X2 = 41.1, p <0.001) in mean abundances with increasing host length. No fish sex preference was observed for parasite infections in silver kob. Macroscopically, most fish showed no visible symptoms of the parasite infestations. In severe intensities however, lesions of the fins and skin, and signs of haemorrhages were observed. This is the first study of ecto- and endo-parasites of Namibian silver kob A. inodorus. Molecular work and studies including Scanning Electron Microscopy (SEM), histopathology, Health Assessment Index (HAI) and descriptive studies should be done to supplement the findings, identify all the parasites to their species level and determine the nature of infections of the parasites on the fish host. en_US
dc.language.iso en en_US
dc.publisher University of Namibia en_US
dc.title Ecto-and endo- parasites of silver kob (Argyrosomus Inodorus) from northern Namibia (21º 24ºS) en_US
dc.type Thesis en_US

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