An Investigation of arctic char (Salvelinus alpinus) and lake trout (Salvelinus namaycush) in Lake Clark National Park, Alaska

Kreiner, Ryan

Anadromous sockeye salmon (Oncorhynchus nerka) are a keystone species for freshwater ecosystems, and in Lake Clark National Park, Alaska (LCNP), declines in salmon runs over the past 25 years have raised concerns about the health of resident fish species. Arctic char (Salvelinus alpinus) and lake trout (Salvelinus namaycush) growth rates and conditions were collected from six lakes within Lake Clark National Park, Alaska (LCNP), and compared among lakes and to historical information (Russell 1980). Four hypotheses were investigated: 1) arctic char and lake trout growth rates would be higher in lakes with sockeye salmon than in lakes without them; 2) arctic char and lake trout condition would be higher in lakes with sockeye salmon than in lakes without them; 3) arctic char and lake trout condition in 2004 would be lower than condition in 1978-79 in lakes with sockeye salmon coincident with declines in anadromous fish runs; 4) arctic char and lake trout diets would consist of sockeye salmon fry and eggs in those lakes with sockeye salmon. Growth and condition of arctic char populations in 2004 were not found to be higher in the presence of salmon, despite an observed seasonal food source of salmon eggs. Historically (1978-79) however, condition was higher in such lakes, coincident with higher salmon runs. As salmon runs have declined, other factors such as predation by lake trout and competition from various whitefish species (Coregonus spp., Prosopium spp.) may contribute more to the growth and condition of arctic char. Growth rates of lake trout were not found to be higher in the presence of salmon, but condition was higher in a lake in which lake trout fed exclusively on salmon fry. This higher condition did not result in larger fish, however. Instead, larger lake trout were associated more with larger lakes and more diverse prey species.