Six hundred and seventy nine specimens of Platichthys flesus (L.) were caught in summer (July–September) 1998 and 1999 from three regions of the Polish zone of the Baltic Sea: the Gulf of Gdańsk, the Pomeranian Bay and the open sea off Łeba. The biometric measurements (length, weight, age) and sex of the specimens were recorded. The specimens were examined for occurrence of parasites. The intensity, relative density and prevalence of infection were calculated.

Specimens of £ounder Platichthys £esus were randomly sampled from three regions of the southern Baltic Sea: the Gulf of Gdan¤ sk, the Pomeranian Bay, the open sea o¡ L Àeba and from the northern Òresund, Kattegat. The collected parasites were morphologically identi¢ed and their genotypes at seven loci coding for enzymes were checked. Wide ranges in both the numbers of rows of rostellar hooks and the numbers of rostellar hooks per row were detected, indicating the presence of two species in the material: Pomphorhynchus kostylewi and Pomphorhynchus laevis. However, electrophoretic data does not support occurrence of two independent gene pools.

Fatty acid and phytosterol vegetable oils were extracted from seeds of Cucurbita pepo (or pumpkin) into (v/v) hexane. The extract obtained was characterized by the contents of sterols, unsaturated and saturated fatty acids. The content of the bioactive compounds was determined by gas-chromatography FID method. Pumpkin seed oil extracts showed higher content of poly-unsaturated fatty acids (49.10%) than that from saturated fatty acids (28%). Sterols exhibited different molecules dominated by β-sistostérol (47%), Stigmastérol (23.6%) and campesterol (21.5%). Several peaks were present on the FID GC chromatogram of two extracts (fatty acids and sterols respectively). GC spectra confirmed the presence of the predominant bioactive compounds (PUFA, β-sistostérol , Stigmastérol and campesterol). The composition of pumpkin seed oil extract was characterized by FID-GC spectra with maximum at 280 nm.