Odzywianie sie juwenalnych hybrydow lososia i troci wedrownej w cieku Chojnowka

The contents of the digestive tracts of juvenile (0+and 1+) hybrids of Atlantic salmon (Salmo salar L.) and migratory sea trout (Salmo trutta trutta L.) were analyzed in three seasons of the year - winter, spring, and fall. The condition co-efficient of the fish analyzed was high in each season, which is evidence that these fish feed well. The good condition of the juveniles was also evidenced by the relatively rich content of the digestive tracts and the index of digestive tract fullness. The highest mean value of digestive tract fullness was confirmed in the juveniles in spring, while the lowest was noted in fall. The food spectrum of the analyzed hybrids comprised a total of 14 taxa of macroinvertebrates throughout the study period. In winter and spring the largest share of the juvenile food was of larval Plecoptera, while the largest share in fall was of amphipods. Larval Plecoptera were confirmed in the stomachs of the largest number of fish. These were followed by amphipods, then larval flies, and larval mayflies. The results of the current study indicate that the dietary composition of juvenile salmon and migratory sea trout hybrids does not generally differ from the diets of either salmon or migratory sea trout.