See - "Productivity and life history of sockeye salmon in relation to competition with pink and sockeye salmon in the North Pacific Ocean" Canadian Journal of Fisheries and Aquatic Sciences, Volume 72, Number 6, June 2015.
I don't know if this paper has been discussed before so I apologize if it has. In brief it points out that sockeye salmon returns to rivers from Alaska to Washington have almost all declined over the past 50 years and in particular since the 1970's. It tests the hypothesis that much of this decline is due to competition with pink salmon for food in the open ocean (one mechanism that can operate on such a large geographical scale). There is strong support for this hypothesis. So, as Alaska, Russia and others dump more pink salmon (and chum salmon) into the ocean, the shift the returns to increases in their local waters at the expense of other areas (WA, BC).
Here's the key points - quoted from the discussion:
"The productivity of sockeye salmon populations in BC, Southeast Alaska, and Washington has declined similarly over time and intensified in recent years, suggesting that the primary causal mechanism driving this decline operates at a large, multiregional spatial scale at sea (Peterman and Dorner 2012). We examined the productivity and life history characteristics of up to 36 sockeye populations — including 18 Fraser River populations — spanning this region of similar trends in productivity over the past 55 years to test whether competition between pink and sockeye salmon for resources at sea may have contributed to these declines. We found consistent evidence that productivity of these sockeye salmon populations has declined in response to increasing abundance of pink salmon in the North Pacific Ocean. Furthermore, length-at-age of male and female Fraser River sockeye salmon was inversely correlated with both pink and sockeye salmon abundance, and age-at-maturity of Fraser River sockeye salmon was positively correlated with pink salmon abundance. These findings were consistent for both detrended and raw datasets involving North Pacific pink salmon, indicating that the influence of pink salmon was detected across both short and long time scales. The abundance of pink salmon in the North Pacific alternates from high (odd-numbered years) to relatively low abundance (even-numbered years), and this alternating-year pattern was also observed in sockeye salmon productivity, length-at-age, and age at maturity. Thus, the evidence for competition between pink and sockeye salmon comes from both hierarchical modeling of patterns over time and the natural experiment provided by the 2-year life cycle of pink salmon and its alternating-year abundance. Our analyses predict that an increase in pink salmon abundance from 150 million to 600 million fish (i.e., the observed range) would lead to a ~67% reduction in total abundance of returning Fraser River sockeye salmon (catch and spawning escapement combined) after controlling for other variables in the model such as parental spawning abundance." (emphasis added).
Note that since about 1980, Alaska's hatchery plants have gone from ~100million to about 1.6 billion and that most of those plants are chum and pink. While the paper doesn't provide an analysis of the impact of chum on other on sockeye nor the impact of either on chinook abundance, one might anticipate that other species would also be affected (either directly through competition for squid and forage fish or indirectly via impacts of hatchery salmon on krill in competition with squid).
I don't know if this paper has been discussed before so I apologize if it has. In brief it points out that sockeye salmon returns to rivers from Alaska to Washington have almost all declined over the past 50 years and in particular since the 1970's. It tests the hypothesis that much of this decline is due to competition with pink salmon for food in the open ocean (one mechanism that can operate on such a large geographical scale). There is strong support for this hypothesis. So, as Alaska, Russia and others dump more pink salmon (and chum salmon) into the ocean, the shift the returns to increases in their local waters at the expense of other areas (WA, BC).
Here's the key points - quoted from the discussion:
"The productivity of sockeye salmon populations in BC, Southeast Alaska, and Washington has declined similarly over time and intensified in recent years, suggesting that the primary causal mechanism driving this decline operates at a large, multiregional spatial scale at sea (Peterman and Dorner 2012). We examined the productivity and life history characteristics of up to 36 sockeye populations — including 18 Fraser River populations — spanning this region of similar trends in productivity over the past 55 years to test whether competition between pink and sockeye salmon for resources at sea may have contributed to these declines. We found consistent evidence that productivity of these sockeye salmon populations has declined in response to increasing abundance of pink salmon in the North Pacific Ocean. Furthermore, length-at-age of male and female Fraser River sockeye salmon was inversely correlated with both pink and sockeye salmon abundance, and age-at-maturity of Fraser River sockeye salmon was positively correlated with pink salmon abundance. These findings were consistent for both detrended and raw datasets involving North Pacific pink salmon, indicating that the influence of pink salmon was detected across both short and long time scales. The abundance of pink salmon in the North Pacific alternates from high (odd-numbered years) to relatively low abundance (even-numbered years), and this alternating-year pattern was also observed in sockeye salmon productivity, length-at-age, and age at maturity. Thus, the evidence for competition between pink and sockeye salmon comes from both hierarchical modeling of patterns over time and the natural experiment provided by the 2-year life cycle of pink salmon and its alternating-year abundance. Our analyses predict that an increase in pink salmon abundance from 150 million to 600 million fish (i.e., the observed range) would lead to a ~67% reduction in total abundance of returning Fraser River sockeye salmon (catch and spawning escapement combined) after controlling for other variables in the model such as parental spawning abundance." (emphasis added).
Note that since about 1980, Alaska's hatchery plants have gone from ~100million to about 1.6 billion and that most of those plants are chum and pink. While the paper doesn't provide an analysis of the impact of chum on other on sockeye nor the impact of either on chinook abundance, one might anticipate that other species would also be affected (either directly through competition for squid and forage fish or indirectly via impacts of hatchery salmon on krill in competition with squid).
