ИСТИНА

The parasite fauna of marine fish in the proximity of the White Sea Biological Station of the Lomonosov Moscow State University has been repeatedly studied by both employees and students of the station. However, accurate quantitative data on infection rates are not available in most published sources. This work is devoted to metazoan parasites (cestodes, digeneans, nematodes, acanthocephalans, leeches and copepods) of cod Gadus morhua, navaga Eleginus nawaga and shorthorn sculpin Myoxocephalus scorpius, caught in July–August 2021 in the shore area of the Velikaya Salma Straight. A total of 50 cods, 50 navagas and 21 sculpins were dissected using standard methods. Parasites were fixed in 4% formalin and 96% ethanol. Specimens for the genetic analysis were stored at ‒20oC. So far we have only preliminary results. Among digeneans the most common were Lepidapedon elongatum (prevalence in cod 74%, in navaga 54%), Hemiurus levinseni (prevalence in cod 80%, in navaga 18%, in shorthorn sculpin 76.2%) and Prosorhynchus squamatus (prevalence in shorthorn sculpin 90.5%). Among tapewoms, the most common were Pyramicocephalus phocarum (prevalence in cod 16%, in navaga 4%, in sculpin 14.3%) and Bothriocephalus scorpii (prevalence in shorthorn sculpin 81%). The most common acanthocephalan was Echinorhynchus gadi (prevalence in cod 74%, in navaga 46%, in shorthorn sculpin 9.5%). All fish specimens were infected with anisakids. Surprisingly, hirudineans were also present, which is quite interesting because we only found one record of sea leeches parasitizing fish in the White Sea. On the other hand, monogeneans that were multiply recorded before by many researchers were not found. Navaga and cod were studied in two time frames — from July 25 to August 15 and from August 16 to 30 — 25 individuals in each period. Prevalence of navaga with trematodes and acanthocephalans increased by 1.5–2 times in the second period, however, the intensity of the infection was lower by 50%. The prevalence with cestodes was four times lower in the second period: the prevalence with acanthocephalans decreased by 28% and the intensity decreased by 2 times. These values can either be a manifestation of the seasonal dynamics of infection, or a consequence of a small sample. Further processing of the material will provide a complete picture of the infection of the studied fish species.