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.