Historically, large numbers of salmon returned to spawn in their natal streams. after providing fertilized eggs for the next generation, the adults died leaving behind nutrient-rich carcasses. These replenished the entire watershed with organic nutrients on an annual basis. A large varient of organisms (insects, fish, birds, mammals) fed on the carcasses, while aquatic and terrestrial invertebrates and plants thrived on the released nutrients.

Recent studies show that spawned-out salmon carcassses provide direct food to salmon juveniles and play a key role in maintaining the productivity of salmonid ecosystems. Rearing juveniles consume salmon eggs, feed directly on spawned-out carcasses, and benefit from increased abundance of aquatic invertebrates and algal growth. The presence of carcasses in streams is related to increased juvenile density, growth rate and body size; larger size of juveniles means improved over wintering survival and ultimately increased marine survival to maturity.