The Ecology of Pacific Salmonids

Salmonids, including Pacific salmon and trout, are an important component of the ecological function and economy for western North America. Salmon and trout of the Pacific Coast have evolved in spite of natural disturbances such as floods, fires, volcanoes, wind-throw and disease. In fact, these influences have helped each species maintain their resiliency.

Natural disturbances tend to be relatively severe but localized, allowing for ecosystem recovery. However, human-caused disturbances may have a magnitude so great that irreversible changes to the aquatic community may occur or increase the severity of impacts from natural disturbances (e.g., flooding), having both acute and chronic impacts to salmonids. Human activities can also cause such widespread gradual changes across the landscape that the recovery potential of individual ecosystems or their components, including salmonid stocks, is altered.

While each salmonid species is unique, the genetic diversity within species across drainages may be as significant as those found across different species. Yet, certain fundamental biological requirements are the basis for all management, recovery or protection initiatives for salmonid streams. This course provides a greater understanding of:

• The life stages of salmon and trout in both coastal and inland streams, and the habitat requirements applicable to each stage

• How substrate quality and hydraulic flow affect spawning behavior and redd success

• How habitat features, instream complexity, bank structure and large woody debris influence success of salmonids at different life stages

• How water chemistry, water temperature and food availability impact trout and salmon behavior and/or physiology

• How migration patterns can be impeded or enhanced by changes in flow, water quality, barriers or obstacles