New marine nearshore study affirms salmon reliance on entire ecosystem

Newly released research provides insight into how juvenile salmon use Central Puget Sound nearshore marine areas and provides evidence that it is the entire nearshore ecosystem, and not individual habitats or small areas within it, that supports salmon.

The report, titled Juvenile Salmon Composition, Timing, Distribution, and Diet in Marine Nearshore Waters of the Central Puget Sound in 2001-2002, concludes that juvenile salmon use a diverse array of nearshore habitat types that have been significantly altered by human development activities. It connects salmon and both land and aquatic environments, which serve to support salmon and other species in the nearshore. For example, the report affirmed that juvenile chinook depend on food from both marine riparian vegetation on land and shallow water habitats such as eel grass.

Released in August, the study was intended to increase understanding about the early life history of salmon in the Puget Sound. Jim Brennan, the senior ecologist for King County Department of Natural Resources and Parks who led the research, said the study will be valuable for natural resource managers working to evaluate factors affecting the decline of salmon and helpful in shaping actions toward recovery.

"While it is generally agreed that early life stages in the marine environment are critical to the survival and productivity of salmon, we wanted to know more about the composition, timing, distribution and diet of young salmon in marine nearshore waters prior to the study," he said. "This research illustrates the linkages between aquatic and terrestrial ecosystems and the importance of managing the nearshore landscape from a regional perspective."

The King County Department of Natural Resources and Parks, and WRIAs 8 and 9 Watershed Forum of Local Governments through the King Conservation District funded the research. The study included 591 sets of beach seine netting along the shores of King County, including Vashon and Maury islands, and south Snohomish County. Between spring and fall of 2001, and spring into winter of 2002, nine species of salmonids were captured in the seining – chum, pinks, chinook, coho, cutthroat, sockeye, steelhead, Bull trout and Atlantic salmon. The fish were measured, weighed, checked for coded wire tags to distinguish between hatchery and wild fish, and checked for stomach contents.

Among the interesting findings shared in the report:

• Juvenile chinook were found for extended periods of time and found to use shallow shoreline areas of Puget Sound. Water currents may help explain the larger distribution patterns of juvenile salmon in the Central Puget Sound area.
• Juvenile chinook stocks are broadly distributed and intermix in central Puget Sound. Coded wire tagged chinook recaptured in the study area originated from 22 different hatcheries and 13 different watersheds
• Hatchery chinook are more abundant than wild chinook in the nearshore.
• Juvenile chinook have diverse diets that are a product of the diverse habitats that make up the nearshore ecosystem.
• Chinook appear to feed opportunistically on whatever prey are seasonally available and shift from a diet of insects, marine plankton and epibenthic organisms to fish at approximately 130-150 mm in size.
• Juvenile chinook depend on food from both marine riparian vegetation on land and shallow water habitats such as eel grass.
• Hatchery and wild chinook significantly overlap in space, time, and diet in the marine nearshore.

The study also recommends actions to protect or improve nearshore habitat for juvenile salmon, suggests that marking and coded wire tagging programs should be more consistent, and that more research is needed to aid in scientifically-based decision making. It recommends protection actions through regulation, enforcement, acquisitions, incentive programs and public education.

The entire 168-page report is available online for public review by visiting Juvenile Salmon Composition, Timing, Distribution and Diet in Marine Nearshore Waters of the Central Puget Sound in 2001-2002.