Ecto- And Endo-Parasites Of Silver Kob (Argyrosomus Inodorus) From Northern Namibia (21° - 24°S)

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