Aquatic Insect Production as Related to Pacific Salmon Spawning and Carcass Availability: Insights from Reseach to Date

The critical role that spawning anadromous salmon play in the productivity and trophic dynamics of freshwater systems is now broadly recognized, and has been widely studied over the last three decades.  Adult salmon migrate from the ocean into the cool, often oligotrophic streams of western North America to spawn and die, providing these systems with a dependable influx of marine derived nutrients in the form of adult salmon carcasses and salmon eggs.  This material can affect stream trophic dynamics and aquatic insect communities both directly and indirectly.  Salmon carcasses and eggs are directly consumed by a variety of freshwater organisms including some aquatic invertebrates.  As salmon carcasses decompose, organic matter is released and sorbed onto the streambed where it becomes available to grazing aquatic invertebrates.  Organic matter derived from salmon eventually is mineralized, becoming available for intake by aquatic plants.  These plants, in turn, are consumed by some aquatic invertebrates.  Research has shown that access to marine derived nutrients and organic matter from spawning salmon can positively impact aquatic invertebrate communities in a variety of ways; resulting in greater abundance, increased growth rate, more rapid development, higher fecundity, and larger size.  As aquatic invertebrates serve as a primary food source for other organisms, these impacts can positively affect aquatic and riparian systems as a whole.  In this talk we will summarize the published research to date on this topic, and identify and discuss areas for potential work in the future.