Incorporating Spatial Structure and Diversity into Recovery Planning for Anadromous Pacific Salmonids

Four criteria are used to evaluate viability during recovery planning for anadromous Pacific salmonid Oncorhynchus spp. populations listed under the U.S. Endangered Species Act: abundance, productivity, spatial structure, and diversity. Better approaches to evaluate spatial structure and diversity are needed so that potential outcomes of recovery actions can be more fully evaluated. In this chapter, we describe several approaches to evaluating spatial structure and diversity in recovery planning using data that were currently available from salmonid population modeling efforts and spatial analyses, especially of habitat data. We employed a case history approach using information developed during recovery planning for the Chinook salmon O. tshawytscha Evolutionarily Significant Unit (ESU) in Puget Sound. Multiple metrics of spatial structure and diversity were developed from outputs of fish population models and spatial habitat data for different land use scenario. We included analyses at several spatial scales. At the population level, we evaluated spatial structure and diversity of two Chinook salmon populations associated with the Snohomish River Basin, the Skykomish and Snoqualmie. We found that changes in spatial structure and diversity varied between the two populations when historical (baseline) and current conditions (a future condition expected if no significant changes occurred in the present rate and type of land use actions) were compared. Changes were more pronounced for the Skykomish population than for the Snoqualmie population. At the watershed scale, we analyzed changes in ecological diversity in six watersheds. of the six watersheds considered, there was little evidence of a change in ecological diversity between historical and current habitat conditions (as reflected by changes in adult spawner and juvenile rearing capacities) in three watersheds (Dungeness, Snohomish, and Stillaguamish) while a more significant change in diversity was indicated in three other watersheds (Green, Puyallup, and Elwha). Changes in spatial structure of the Puget Sound ESU were indicated between historical and current conditions when comparing the proportion of spawners associated with each of the five biogeographical planning units. We recommend future work is needed to evaluate the effects of hatcheries and harvest on spatial structure and diversity, develop and test other metrics, and include other life stages such as those associated with estuarine and Puget Sound habitats.