Abstract Title

Session S-08D: Salmon Recovery: Implementation and Progress I

Keywords

Species and Food Webs

Start Date

2-5-2014 8:30 AM

End Date

2-5-2014 10:00 AM

Description

Estuarine wetlands in the Salish Sea provide important rearing habitat for migrating juvenile Pacific salmon, contributing to their overall productivity and ocean survival. Substantial loss of historical estuarine habitat in the Salish Sea due to diking, draining and development has contributed to the decline of Pacific salmon populations (Oncorhynchus spp.). The return of tidal inundation through a series of dike removals to 364 hectares of the Nisqually River Delta (Olympia, Washington, USA) represents one of the most significant advances to date towards the recovery of the threatened Nisqually Fall Chinook stock. Our objective was to assess the collective Nisqually Delta restorations in terms of increased rearing opportunity for juvenile salmon. Metrics consisted of physical conditions that allow juvenile salmon to access the estuarine restorations such as delta connectivity, full tidal inundation and channel development. Unlike most studies, we put these physical metrics in terms of juvenile Chinook by constraining our inundation model to outmigration season (Mar – Aug) and those tidal depths supporting juvenile Chinook (> 0.4 m). We used these criteria, verified by presence of juvenile salmonids in three restored and two reference tidal channels, to measure the change in opportunity potential from pre-restoration to post-restoration condition for juvenile Chinook to access and rear in the Nisqually estuary. We found landscape connectivity to be strongly tied to tidal height and increased throughout the estuary with dike removal. Tidal channel development was most rapid in the first and second year post-restoration; with channel outlets widening and deepening to accommodate restored tidal prisms. Chum salmon, natural origin Chinook and hatchery origin Chinook salmon accessed all three restored marshes within two years post-restoration, although responses varied among years, marshes and salmon species. These results suggest that the Nisqually Delta restorations are providing increased rearing opportunity for juvenile salmon.

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May 2nd, 8:30 AM May 2nd, 10:00 AM

Restoration of the Nisqually River Delta and increased rearing opportunities for salmonids

Room 611-612

Estuarine wetlands in the Salish Sea provide important rearing habitat for migrating juvenile Pacific salmon, contributing to their overall productivity and ocean survival. Substantial loss of historical estuarine habitat in the Salish Sea due to diking, draining and development has contributed to the decline of Pacific salmon populations (Oncorhynchus spp.). The return of tidal inundation through a series of dike removals to 364 hectares of the Nisqually River Delta (Olympia, Washington, USA) represents one of the most significant advances to date towards the recovery of the threatened Nisqually Fall Chinook stock. Our objective was to assess the collective Nisqually Delta restorations in terms of increased rearing opportunity for juvenile salmon. Metrics consisted of physical conditions that allow juvenile salmon to access the estuarine restorations such as delta connectivity, full tidal inundation and channel development. Unlike most studies, we put these physical metrics in terms of juvenile Chinook by constraining our inundation model to outmigration season (Mar – Aug) and those tidal depths supporting juvenile Chinook (> 0.4 m). We used these criteria, verified by presence of juvenile salmonids in three restored and two reference tidal channels, to measure the change in opportunity potential from pre-restoration to post-restoration condition for juvenile Chinook to access and rear in the Nisqually estuary. We found landscape connectivity to be strongly tied to tidal height and increased throughout the estuary with dike removal. Tidal channel development was most rapid in the first and second year post-restoration; with channel outlets widening and deepening to accommodate restored tidal prisms. Chum salmon, natural origin Chinook and hatchery origin Chinook salmon accessed all three restored marshes within two years post-restoration, although responses varied among years, marshes and salmon species. These results suggest that the Nisqually Delta restorations are providing increased rearing opportunity for juvenile salmon.