Preliminary analysis of ectoparasites of the sturgeon Acipenser oxyrinchus oxyrinchus (Mitchill, 1815) originating from different water habitats.

The purpose of this study has been to carry out a preliminary parasitological analysis of sturgeon specimens in the context of the presence of external parasites, and to determine their possible influence on the health of the fish. The examination of external parasites was performed on specimens of A. oxyrinchus oxyrinchus captured from an open system pond (the Fish Farm in Kuźniczka, Poland) and from the St John River (Canada), in the spring and summer of 2008. Mucus collected from the skin surface of the pectoral fin and around the gills of A. oxyrinchus oxyrinchus individuals was fixed in 30% ethyl alcohol. The preparations were examined under a microscope. In total, 227 specimens of parasites were isolated from the skin of A. oxyrinchus oxyrinchus. The parasites belonged to three taxa: Protozoa, Monogenea and Crustacea. The degree of parasitic infestation by particular parasites in the analyzed samples ranged from 27.2 to 100%, and the value of the mean infestation varied from 1 to 13.6. Among the determined parasites, Trichodina sp. were characterized by the highest parasitological parameters. The other determined protozoan, i.e. Apiosoma sp., was found on the skin of half the examined individuals of A. oxyrinchus captured from the flow-through pond. Several individuals of the monogenetic fluke Gyrodactylus sp. were found on the skin of A. oxyrinchus oxyrinchus originating from the pond. Ergasilus sieboldi was identified in the samples obtained from both water habitats. Three individuals of the crustacean Argulus coregoni were observed on the skin of fish captured in the St John River.