Efekty zarybiania pstragiem potokowym [Salmo trutta m.fario L.] rzek Pomorza [Kaszuby] i Suwalszczyzny

The effectiveness of stocking brown trout summer fingerlings (0.5-1.3 g) into six moraine Pommeranian rivers was evaluated. Three groups of experimental fish were marked with alizarine red S to enable their identification during autumn and spring monitoring with electrofishing. The results indicated that stocking was more effective when done with summer fingerlings than one- year-old fish. In the three investigated rivers stocking resulted in 3.5 to 13.5 young-of-the-year trout increment. In two cases the share of stocked fish was lower than these from natural spawning.