Marzena Haluch and Krzysztof  SKÓRA
Marine Station of the Institute of Oceanography of Gdańsk University, Morska 2, 84-150 Hel, Poland

Key words: fish, Salmo trutta, food composition, Baltic Sea.

Abstract.
In the season of 1994-1995, studies were conducted on the food of sea trout (Salmo trutta L.) caught in drift-nets on  four traditional fishing grounds of the Gulf of Gdańsk: the Vistula river mouth in the �wibno area, the Reda river mouth in Puck Lagoon, Puck Bay, and the Gdańsk Deep. Total length (TL) of fish caught ranged from 40 to 122 cm (mean: 67.7 cm), with the 65 cm length-class dominating. A total of 907 fish were examined, of which only 342 had food in their stomachs.
Fish in the open waters of the Gulf of Gdańsk fed most intensively (85.7%). Toward the shore the number of sea trout with full alimentary canals was decreasing - to 40.7% in Puck Bay, and 20.2% and 18.9% in the estuarial areas of the Reda and Vistula rivers. The main component of the food of sea trout was the Clupeidae. They constituted 78.2% of the share in weight and 68.2% of the share in numbers of the components determined. The food composition was supplemented by Ammodytidae (of secondary importance), constituting 12.6% in weight and 8.7% in numbers.
Among other fish species identified being components of the sea trout diet, Gasterosteus aculeatus should be mentioned, on which sea trout of Puck Bay fed. The share of this component in the food of fish from this fishing ground was 1.6% in weight and 5.6% in numbers of the food eaten.