Fisheries scientists say the abundance of salmon in the North Pacific Ocean is at the highest ever, but given climate changes and more, there are many unanswered questions about the effect of hatchery stocks on wild salmon.
It’s a topic of continuing discussion that came up at the recent Alaska Chinook salmon symposium in Anchorage, and some prominent researchers associated with the University of Washington are hoping research into this matter continues at an international level.
Retired UW professor Kate Myers, who participated in one of the salmon symposium panels, said scientists don’t really understand how carrying capacity of the ocean is fluctuating with climate change, and some scientists want a more international focus on this issue because stocks from many countries are overlapping.
Daniel Schindler, a professor at UW’s School of Aquatic and Fishery Sciences, also sees a need for more research into how hatchery stocks affect wild stocks.
The ramp up in hatchery production has happened mostly since the mid 1970s, and has coincided with the North Pacific Ocean being in a very productive phase for salmon, so the more smolts put out there, the more that came back, Schindler said.
The big question now is how climate change and Pacific Decadal Oscillation will affect salmon stocks, including the prized Chinooks. Pacific Decadal Oscillation is a pattern of Pacific climate variability that shifts phases on at least inter-decadal time scale, usually about 20 to 30 years. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 20 degrees north. During a “warm” or “positive” phase, the west Pacific becomes cool and part of the eastern ocean warms. During a “cool” or negative phase, the opposite pattern occurs.
Schindler said there are good indications that the North Pacific is starting to slide back into a slow phase, a cool PDO phase, and the cool phase is not so good for Alaska salmon. More research is needed to learn how ocean carrying capacity is affected and whether hatchery production should be adjusted with changes in the PDO.