Effects of habitat on individual reproductive success of mature male parr of Atlantic salmon Salmo salar.

The effect of the presence of stone blocks in the spawning habitat on the reproductive success of mature male parr of Atlantic salmon Salmo salar of various sizes and ages was tested in an artificial channel. Shelters allowed smaller individuals to contribute to egg fertilization as much as large parr, suggesting that the size-based dominance observed in a shelterless habitat was not maintained in a more complex habitat.