Salmon in the Ecosystem

Salmon and Trout in the Ecosystem

Lamberto Garcia

Pierce College

Abstract

The population structure of Chinook salmon and Steelhead trout is presented as an assimilation of the life history forms that have evolved in diverse and complex environments over their Pacific range. Temperature is described as the overwhelming environmental influence that determines what life history options occur. The different populations represent ecological type’s referred to as spring, summer, fall, and winter-run segments, as well as stream and ocean type, or stream and ocean-maturing life history forms. However, they are more correctly described as a continuum of forms that fall along a temporal cline related to development and rearing temperatures that determine spawn timing and juvenile residence patterns. Population structure of Chinook salmon and Steelhead in the Columbia Basin, therefore, is the reflection of the genetic composition of the founding source or sources within the respective region, shaped by the environment, principally temperature that defines life history evolutionary strategy to maximize fitness under the conditions delineated. The key in developing an effective recovery program for Chinook salmon and steelhead is to recognize that measures taken must address the genetic and biological requirements of the population unit within the environmental template identified.

The Pacific salmonids evolved with the Pacific ecosystem under very dynamic and harsh conditions that are believed to have had overwhelming influences on the evolution of the salmonid species, life history strategies, and the population structure that each ultimately developed. The dynamics of plate tectonics and geological formations peculiar to the Northeastern Pacific Rim created opportunities for speciation among salmonids that have resulted in seven anadromous oncorhynchids distributed over a range from the Arctic to lower California, with four oncorhynchids becoming stream dwellers...