Parasites of young Baltic cod, Gadus morhua callarias L. in the Gulf of Puck, Poland

Background. The hitherto published records of the parasite fauna of Baltic cod, Gadus morhua callarias cover commercially-caught adult fish. The aim of this study was to determine the composition of the parasite fauna of young Baltic cod, the relevant infection parameters and to relate those data to published records on the diet of cod. Materials and methods. This survey was carried out on 154 young cod, caught in May and June 2002 in the Gulf of Puck, the Baltic Sea, Poland. The fish were examined using standard methods applied in parasitology. Results. No external parasites were found. In the digestive tracts of 58 cod, 3 species of parasites belonging to 2 higher taxa (Nematoda and Acanthocephala) were found. The dominant parasite was Echinorhynchus gadi Zoega in Müller, 1776. The mean abundance ranged from 0.15 to 2.75. The prevalence ranged from 14.6%, in the smallest fish, to 66.7% in the larger ones. Only two acanthocephalan specimens of Pomphorhynchus laevis (Zoega in Müller, 1776) and five nematode larvae of Hysterothylacium aduncum (Rudolphi, 1802) were found. Conclusion. The parasite fauna of young Baltic cod is significantly sparser than in larger fish examined by other authors. It is suggested that the occurrence of the species found, can be related to the composition of diet available.