The Effect of Salmon Carcasses on Alaskan Freshwaters

Abstract

Many Alaskan freshwaters provide important spawning and nursery habitat for salmonid fishes. Pacific salmon are well known for their anadromous and semelparous natural history of rearing in the marine environment and returning to freshwater as adults to spawn once before dying in their natal habitat. Five species of anadromous Pacific salmon, Oncorhynchus nerka (sockeye or red salmon), O. kisutch (coho or silver salmon), O. gorbuscha (pink or humpback salmon), O. keta (chum or dog salmon), and O. tshawytscha (chinook or king salmon) spawn in Alaskan freshwaters. The time juvenile salmon reside in freshwater following emergence from the gravel as fry until smoltification (physiological preparation for migration to saltwater) depends on species and location. Because freshwater residence can range from virtually no time to several years, considerable variation in dependence on the freshwater habitat as a nursery environment exists. The sockeye salmon is the only Pacific salmon to have a juvenile stage that is usually dependent on a lacustrine habitat and a forage base of Zooplankton. Because lakes used for rearing by juvenile salmon are typically olig-otrophic, the productivity of sockeye lakes has been studied as a factor limiting sizes of salmon runs (see Chapter 8; and Burgner et al., 1969; Hyatt and Stockner, 1985; Stockner, 1981, 1987