Helminth fauna of saffron cod <i>Eleginus gracilis</i> in the coastal waters of the Magadan Region (northern coast of the Okhotsk Sea)

Abstract

Results of parasitological investigation of saffron cod Eleginus gracilis Tilesius, 1810 are presented. The fish samples were collected in 6 distanced marine areas at the coast of Magadan Region, generally corresponded with local stocks or herds of this species. In total, 29 helminth species are identified, including 8 cestodes, 11 trematodes, 5 nematodes, and 5 acanthocephalans. The highest species diversity of helminths is detected for the saffron cod from the Odyan Bay (24 species) and the lowest – for the saffron cod from the Amakhton Bay (16 species). Occurrence and intensity of infestation is the highest for trematodes Hemiurus levinseni, Podocotyle reflexa, and Brachyphallus crenatus, nematodes Ascarophis pacifica, and acanthocephalans Echinorhynchus gadi and Corynosoma strumosum. The number of detected worm species is close to the total number of these parasites recorded for saffron cod in the Far-Eastern Seas and adjacent Pacific – 33 species (excluding monogeneans). Cestodes Diplocotyle olrikii, trematodes Bucephaloides iskaensis, and acanthocephalans Bolbosoma caenoforme are registered for the first time for saffron cod in the Okhotsk Sea. There is found for the first time in the studied area that saffron cod is a definitive host for trematodes Steganoderma formosum and a paratenic host for acanthocephalans Andracantha mergi. Eight species dangerous from medical and (or) veterinary point are detected: Nybelinia surmenicola, Diphyllobothrium sp., Pyramicocephalus phocarum, Anisakis simplex, Pseudoterranova decipiens, Bolbosoma caenoforme, Corynosoma semerme, and C. strumosum. The data on helminth infestation are not useful for differentiation of the saffron cod sub-populations in the northern Okhotsk Sea because of almost permanent partial mixing of these groups.