Life After Death: The Importance of Salmon Carcasses to British Columbia's Watersheds

Résumé

... Adult spawning salmon are a key link between the marine ecosystem and the ecosystems inland. ... As returning adults approach the streams they will enter to spawn, they stop feeding. Their bodies contain only an insignificant amount (<1%) of residual freshwater-derived biomass, accumulated when they were smolts developing in the stream environment .... Thus, the body of an adult salmon is almost entirely constructed from marine sources. These marine-derived nutrients enter the stream ecosystem before, during, and after spawning, through excretion, release of gametes, and carcass decomposition, respectively .... Once released, these marine-derived nutrients become available to enter into the food-web dynamics of both the aquatic and the surrounding terrestrial ecosystems. ... When fewer salmon return to the spawning grounds, smaller quantities of marine-derived nutrients are supplied to the surrounding ecosystems. Larkin and Slaney (1997) showed that as carcass availability in a stream declined, so did nutrient and carbon sources for developing salmonids. This suggests that salmon parents assist their progeny in the fight for survival long after they are gone themselves. ... I plan to construct an ecosystem model that tracks the flow of marine-derived nitrogen through the stream and adjacent forest ecosystem. The model will focus on converting spawning salmon biomass estimates for a particular stream and using these estimates to calculate the amount of marine-derived nitrogen entering the watershed. The pathways taken by marine-derived nitrogen as it travels throughout and across ecosystems will be compiled into a model, using the Ecopath software. ...