The 2005 Skagit Chinook Recovery Plan (SCRP) was written in response to the 1999 threatened listing of Puget
Sound Chinook Salmon under the Endangered Species Act. The SCRP includes recovery strategies with candidate
actions for geographic areas associated with specific Chinook Salmon life stages, including the Skagit estuary.
Since the SCRP’s inception, stakeholders began implementation of its candidate projects and other projects
consistent with its goals and strategies. Within the SCRP are candidate projects aimed at (a) increasing estuary
habitat area within the Swinomish Channel Corridor (SC) and (b) one project to improve fish migration pathways
between the North Fork Skagit delta and the SC, which is predicted to improve access by juvenile Chinook
Salmon to existing and potential (through restoration) estuarine rearing habitat within the SC and Padilla Bay.
However, several modeling and feasibility studies completed to advance these projects have raised questions
regarding the utility of doing restoration within the SC or reconnecting the SC with the North Fork Skagit delta
on behalf of juvenile Chinook Salmon due the SC’s high salinity water compared other areas in the Skagit estuary.
In part, the questions are a result of two differing approaches used to infer juvenile Chinook Salmon estuary
habitat value for restoration planning purposes. The SCRP used an empirical derived relationship of juvenile
Chinook Salmon density as a function of landscape connectivity while the feasibility and modeling studies used
numeric criteria for physical habitat attributes within hydrodynamic model frameworks to predict fish benefits.
Landscape connectivity is associated with a fish passage ecological function while salinity is associated with the
physiological transition from freshwater to seawater by fish. Both ecological functions are important to juvenile
Chinook Salmon in estuaries, but applying the tools of both approaches did not lead to synchronous answers for
candidate restoration sites.
At the time of SCRP development and its initial restoration implementation phases, inadequate local data were
available to empirically evaluate the strengths and weaknesses between the landscape connectivity and salinity
criteria approaches. However, this study – now eighteen years after the SCRP was published – uses twenty-one
years of juvenile Chinook Salmon observations paired with salinity and landscape connectivity observations
across the Skagit estuary to better inform restoration planning efforts and have resulted in the following keys
findings and opinions.
