Developing Applications for Spatial Structure and Diversity Parameters in Salmon Recovery: a Skagit Chinook Salmon Example

Salmon populations with adequate expression of spatial structure and diversity are considered more resilient to stresses on their population yet few salmon recovery efforts consider these factors in their plans. Spatial structure refers to the geographic distribution of individuals in a population or populations. Diversity (i.e., variability in traits) associated with anadromous Pacific salmon is thought of at three levels: ecological, genetic, and phenotypic (i.e., life history diversity).

We identified the habitat requirements of four different life history strategies of wild Skagit River Chinook salmon. Life history strategies varied largely in how long fish reared in freshwater relative to the estuary or early marine (Salish Sea) life stages. We propose life-stage specific recovery actions to increase abundance levels of each life history strategy rather than optimizing a single life history type. We used field studies of 1) population dynamics by life stage, 2) known life history trajectories including geographic diversity, and 3) current/historic habitat conditions to shape our understanding of each life history strategy. Synthesis of these results has helped develop an overall approach to quantifying objectives for spatial structure and phenotypic diversity of Skagit River Chinook salmon.