Changes in use of lake habitat by experimentally segregated populations of cutthroat trout and Dolly Varden char

Abstract

The role of competition in a lacustrine community of two salmonid species, cutthroat trout Oncorhynchus clarki and Dolly Varden char Salvelinus malma, was studied in three coastal British Columbia lakes Habitat use by the species alone (allopatric) and in coexistence with each other (sympatric) was investigated by gill netting at 0-40 m depth contours (surface to bottom) so that several habitats (littoral, epipelagic. pelagic, epibenthic) were sampled From June to October, trout used mainly littoral and epipelagic habitats in sympatry and allopatry Char used all habitats in allopatry. and deep habitats (pelagic, epibenthic) not frequented by trout in sympatry The two species were thus spatially segregated with depth in sympatry Diel (day, night) and seasonal changes (spring, summer, autumn) in habitat use were not pronounced The shift in habitat use by experimentally allopatric char but not trout suggests that the effects of competition between sympatric trout and char for habitat resources are greater on the char