Does life-history variability in salmonids affect habitat use by juveniles? A comparison among streams open and closed to anadromy
Contribution to the program of CIRSA (Centre Interuniversitaire de Recherche sur le Saumon Atlantique)
*Correspondence and present address: Rescan Environmental Services, Sixth Floor, 1111 West Hastings, Vancouver, BC V6E 2J3, Canada. E-mail: email@example.com
- 1Migratory and resident forms of salmonids coexist in many river systems. Although such coexistence is widespread, little is known about its ecological basis and no studies have compared the habitat use of premigratory juveniles and residents.
- 2We employed a comparative approach to explore the differential habitat use of juvenile anadromous and resident brook trout. This required the investigation of habitat use in streams closed to anadromy, containing only resident brook trout Salvelinus fontinalis (‘resident-only’ streams) and streams open to anadromy, containing coexisting Atlantic salmon Salmo salar and anadromous and resident brook trout (‘migrant-resident’ streams).
- 3We demonstrate that fast habitats (riffles) are occupied more frequently in streams with migratory brook trout relative to riffle habitats of streams with only resident brook trout. In contrast, occupation of slow current velocities (pools) was observed in both migrant-resident and resident-only streams as both stream types contain resident brook trout. The net effect is a wider distribution of occupied habitats (pool and riffles) in migrant-resident streams relative to resident-only streams, resulting in few, if any, unused habitats.
- 4These results are consistent with previously reported bioenergetic, morphological and stable isotope differences observed between anadromous and resident brook trout.
- 5Our findings suggest that a link exists between juvenile habitat use, metabolic costs and life-history strategies.