By Dave Beatty
Although the Salish Sea, the region including Puget Sound and the Strait of Georgia, has been known for its production of Chinook, coho, and steelhead, it became apparent during the last 40 years that marine survival was declining at rates faster than elsewhere along the Pacific Coast. This decline in both natural origin and hatchery origin fish was occurring even though millions of dollars were being expended for freshwater habitat restoration and protection, increased hatchery production and improved hatchery management, and better management of harvest. The failure of many populations’ abundance to significantly and sustainably increase led to the question of why are juvenile Chinook, coho, and steelhead not surviving after they leave the home stream and enter what seems to be the inhospitable environment of the Salish Sea. There has been accumulating evidence that juvenile Chinook, coho, and steelhead must survive during a crucial period after entering seawater. Decreased survival will determine the abundance of adults of the affected species returning later to spawn.
The Salish Sea Marine Survival Project (SSMSP) was initiated in 2014 as a joint effort of Long Live the Kings (LLTK) in Washington and the Pacific Salmon Foundation (PSF) in British Columbia. Collaborating on more than 90 studies, over 200 multidisciplinary scientists representing 60 federal, state, provincial, tribal, nonprofit, academic, and private institutions investigated the interactions of Chinook, of coho, and of steelhead with the Salish Sea ecosystem. It is known that salmonid survival is affected by many factors and determining the ones most likely to be moving certain populations toward extinction is a fundamental challenge. The majority of the SSMSP research was completed between 2014 and 2018. A select committee of US and Canadian scientists then reviewed the research to determine the factors that most likely affect juvenile salmonid survival in the Salish Sea.
Chinook Smolt - Creative Commons -Flickr
The Committee’s principal opinion was those factors connected to food supply and to predation are the major contributors to the decreasing survival of juvenile salmonids. The availability and nutritional value of the juveniles’ food are affected by changing environmental conditions which thereby affect their growth and survival. Of the three species, steelhead seem to be least affected by food; perhaps due their later entrance to the Salish Sea from the home stream followed by movement to the open Pacific Ocean sooner than do Chinook and coho. The large and increasing number of pinnipeds, especially harbor seals, in the Salish Sea are another major survival factor even though these salmonids are only a small part of the seals’ diet. Nonetheless, the very high number of seals cause significant predation in space and time on juveniles.
The SSMSP Select Committee recognized there are many complex interrelationships among the factors of food supply, predation, pollution, disease, hatcheries, river flow, and estuaries that affect the survival of juvenile salmonids in the Salish Sea. Within any single factor, for example food supply, greater understanding of the interrelationship roles of phytoplankton, zooplankton, and forage fish can provide insight to predict future shifts in survival of juveniles during climate change.
Steelhead Smolt- Creative Commons -Flickr
An outcome of the SSMSP research has been the establishing of Key Recommendations that may also benefit other species such as Southern Resident Orcas that are dependent for feeding on adult salmonids, especially Chinook.
Key Recommendations include:
1) “Protect and restore estuary and nearshore habitat”
2) “Recover herring populations and evaluate herring distribution and movement”
3) “Build resilience in salmon by protecting and increasing their diversity”
4) “Continue to assess seal predation, including foraging hot spots, seal diets, and responses to hatchery releases. Implement multiple strategies to reduce seal predation”
5) “Identify toxic contaminant hotspots and sources and focus efforts to reduce the contaminants”
6) “Optimize the health and survival of hatchery-reared salmon”
7) “Protect and manage river flows”
8) “Improve adult salmon return forecasting and guide other eco- system recovery actions with the new data compiled via the SSMSP”
9) “Assess disease in young salmon, especially in the face of climate change”
10) “Continue to assess juvenile Chinook and Coho growth and survival, including survival through winter life-stages, especially as climate change continues to affect our region”
11) “Maintain and improve upon ecosystem monitoring of the Salish Sea”
12) “Continue to test new and novel research techniques and strategies”
Coho Smolt - Creative Commons -Flickr
As more research is accumulated and reviewed, additional key recommendations will be established and further actions will be implemented. Already, the Salmon Health Initiative of the PSF has increased the understanding of diseases in BC’s wild, hatchery, and aquaculture salmon. This led to creating the technology to monitor the salmonids’ heath and condition. A study of steelhead smolt predation has been undertaken by LLTK. Other actions include assessments of blockages for downstream passage of juveniles. Furthermore, SSMSP collaborators are developing new deterrents for predators; new strategies are being tested for managing the release of hatchery Chinook and coho; there are actions to monitor and to increase forage fish throughout the Salish Sea; there are monitoring programs for phytoplankton, zooplankton, and temperature resilient kelp; there is greater monitoring of marine mammals, marine debris and contaminants, and nearshore habitat.
The SSMSP has demonstrated the importance of collaboration within the large group of professional and community-based researchers who represented a broad base of disciplines and authorities. It produced an outcome of ecosystem science that is a departure from the historically fragmented studies of the Salish Sea ecosystem. With respect to this, the collaborators, made another recommendation, “Therefore, we strongly recommend that the region establish and sustain a formal transboundary support structure for ecosystem science”. The SSMSP report indicates systematic collaboration could be achieved through the Salish Sea Science Council together with the Salish Sea Institute at Western Washington University.
For those wishing further elaboration on the SSMSP, go to these three links,
https://marinesurvivalproject.com/research-findings/
"Young Salmon Are Dying In The Salish Sea"
"In a Five-Year, International Research Effort, the Salish Sea Marine Survival Project is finding out Why" https://marinesurvivalproject.com/
"FACTORS LIMITING SURVIVAL OF JUVENILE CHINOOK SALMON, COHO SALMON AND STEELHEAD IN THE SALISH SEA: SYNTHESIS OF FINDINGS OF THE Salish Sea Marine Survival Project" (138 pages) https://marinesurvival.wpengine.com/wp-content/uploads/2021PSF-SynthesisPaper-Screen.pdf
For a video of the LLTK study of steelhead smolt predation
Reports from the SSMSP to the Pacific Salmon Commission are at https://www.psc.org/fund-project/salish-sea-marine-survival-project/