Magnitude and fate of salmon-derived nutrients and energy in a coastal stream ecosystem

Abstract

We quantified the energy and mineral (nitrogen, phosphorous) composition of live pink salmon (Oncorhynchus gorbuscha) and chum salmon (O. keta), their eggs, and carcasses, and tracked the fate of chum salmon spawning in a small Alaskan coastal stream. On average, salmon entered streams with 5.3 kJ·g-−1, 3.3% N, 0.48% P. Much of the energy in female salmon was stored in the gametes because the gonads were both large (20% of their wet body mass) and high in energy density (11 kJ/g). Carcasses following senescent death had lower mass-specific energy and N (but not P) compared to fish at stream entrance. Bears removed nearly 50% of the salmon-derived nutrients and energy from the stream by capturing salmon and dragging the carcasses from the stream. Much of the salmon biomass was made available to riparian scavengers because bears partially consumed the fish. Nutrients bound in salmon tissue at senescent death were quickly exported to the estuary after only a few days because of periodic high flows and low rates of scavenging by bears. © 2004, Copyright Taylor & Francis Group, LLC.