Myoxocephalus scorpius – liver nematodes and diet (pilot studies from Polish waters)

Research on the parasitology of the shorthorn sculpin (Myoxocephalus scorpius) from the Baltic Sea is presently limited. As a predatory fish, the species primarily acquire nematode parasites through the ingestion of infected prey. The main objectives of the current study were to (1) evaluate the presence of nematodes in the livers of shorthorn sculpin from the southern Baltic Sea and (2) investigate the dietary composition of this species. Accordingly, 32 fish from the north-western Polish waters of the Baltic Sea (ICES rectangle 39G6) were caught in November 2020 and subjected to standard ichthyological analyses. Moreover, liver samples were dissected from each fish and frozen for further parasitological investigation. The presence of the parasites was detected in 5 of the 32 analyzed livers, with a prevalence of 15.6%, intensity of infection from 2 to 99 parasites per fish and abundance of 3.9. Co-occurrence of Contracaecum sp. and Hysterothylacium sp. nematodes was observed in all infected fish. Stomach content analysis revealed that Crangon crangon, Bylgides sarsi and Gammarus spp. were the most abundant components of the shorthorn sculpin’s diet.