searun
Well-Known Member
Pinniped populations in the Salish Sea and elsewhere have increased beyond historic levels. Chinook and Steelhead populations have steeply declined in a similar pattern. Hmmm, perhaps one of the stronger contributors to "poor ocean" survival is being uncovered by recent research.
A small clip from research currently underway to augment similar findings in a number of studies underway on both sides of the Canada/US border. Both efforts finding the same result - that pinnipeds are a more significant source of Chinook mortalities than previously thought.
Moreover, we are starting to see harbour seals in particular venturing up into rivers in pursuit of smolts and adults alike.
The Salish Sea Project is starting to uncover a wide variety of causal factors. Everything from predation to over-fishing of the critters in the food chain that help juvenile salmonids thrive (crab larvae, herring, krill).
If we truly want to see Southern Resident Killer Whales (SRKW's) rebound, the answer may rest with a well rounded and disciplined recovery effort that includes increasing smolt production, increasing food sources available to juvenile salmonids, and most importantly significantly reducing pinniped predation.
Check out this research article, and in fact please take the time to read the other research contained on the Salish Sea Project site....this is profoundly enlightening as to the complex issues facing chinook recovery.
https://marinesurvivalproject.com/research_activity/list/predation/
Here's a clip from the paper as a sample - note the significant estimates of chinook/coho mortalities directly attributable to pinniped predation!!!
This team assessed the impact of seals on salmonids in Cowichan Bay by counting the number of predators in the Cowichan Bay, quantifying predation events from visual observations, and determining diets from morphological and genetic analysis of fecal samples. Data collected for 2012-2014 provides the following estimates of the percentage of chinook and coho juveniles lost to seal predation in the Strait of Georgia:
-Chinook: Mean = 40% (95% CI: 32-45%)
-Coho: Mean = 47% (95% CI: 44-52%)
These data have been used in a model developed by PhD student Ben Nelson to test whether pinnipeds are inhibiting the recovery of commercially and recreationally important stocks of Chinook and coho salmon in the Strait of Georgia. Given these estimates, it appears that harbour seal predation is likely responsible for a significant amount of natural mortality in the early marine stage for both Chinook and coho salmon in the SOG. Ben notes that seal predation appears to be highest on juvenile fish between 115-145mm in length, but also cautioned that the consumption estimates and mortality could be biased due to high emphasis on “estuary seals” because of the locations that scats were sampled.
A small clip from research currently underway to augment similar findings in a number of studies underway on both sides of the Canada/US border. Both efforts finding the same result - that pinnipeds are a more significant source of Chinook mortalities than previously thought.
Moreover, we are starting to see harbour seals in particular venturing up into rivers in pursuit of smolts and adults alike.
The Salish Sea Project is starting to uncover a wide variety of causal factors. Everything from predation to over-fishing of the critters in the food chain that help juvenile salmonids thrive (crab larvae, herring, krill).
If we truly want to see Southern Resident Killer Whales (SRKW's) rebound, the answer may rest with a well rounded and disciplined recovery effort that includes increasing smolt production, increasing food sources available to juvenile salmonids, and most importantly significantly reducing pinniped predation.
Check out this research article, and in fact please take the time to read the other research contained on the Salish Sea Project site....this is profoundly enlightening as to the complex issues facing chinook recovery.
https://marinesurvivalproject.com/research_activity/list/predation/
Here's a clip from the paper as a sample - note the significant estimates of chinook/coho mortalities directly attributable to pinniped predation!!!
This team assessed the impact of seals on salmonids in Cowichan Bay by counting the number of predators in the Cowichan Bay, quantifying predation events from visual observations, and determining diets from morphological and genetic analysis of fecal samples. Data collected for 2012-2014 provides the following estimates of the percentage of chinook and coho juveniles lost to seal predation in the Strait of Georgia:
-Chinook: Mean = 40% (95% CI: 32-45%)
-Coho: Mean = 47% (95% CI: 44-52%)
These data have been used in a model developed by PhD student Ben Nelson to test whether pinnipeds are inhibiting the recovery of commercially and recreationally important stocks of Chinook and coho salmon in the Strait of Georgia. Given these estimates, it appears that harbour seal predation is likely responsible for a significant amount of natural mortality in the early marine stage for both Chinook and coho salmon in the SOG. Ben notes that seal predation appears to be highest on juvenile fish between 115-145mm in length, but also cautioned that the consumption estimates and mortality could be biased due to high emphasis on “estuary seals” because of the locations that scats were sampled.