FAIRBANKS, Alaska--For two straight years, returns of sockeye salmon to Bristol Bay, the world's largest wild red salmon fishery, have been below state forecasts. Salmon returns to the Kenai Peninsula, the Yukon-Kuskokwim River and elsewhere in Alaska also have fallen short of expectations.
The declines come as a shock to fishermen and policy makers, but not to some scientists who study the North Pacific Ocean. Their studies of year-to-year and long-term changes in the ocean suggest the salmon declines are in part the result of natural ocean cycles.
"It was bound to happen," says Milo Adkison, an assistant professor of fisheries at the University of Alaska Fairbanks School of Fisheries and Ocean Sciences. "You get large year-to-year variations and you also get shifts in salmon abundance that can run for a couple of decades. Salmon productivity itself is connected to conditions in the ocean that operate on similar time scales."
Adkison says research being done at the University of Alaska Fairbanks suggests the changes in fish and shellfish abundance, called regime shifts, occur about every 20 years. It's been about that long since Alaska's salmon stocks rebounded from historic lows. Adkison says a regime shift might be under way, but it's still too early to tell.
"Because there is such a large interannual variability, you have a hard time knowing that you're in a new regime until you've seen five years of bad returns in a row or five years of good returns in a row," says Adkison.
UAF assistant professor of oceanography Tom Weingartner also isn't ready to say a regime shift is under way, but he has noticed dramatic changes in the ocean.
"Certainly over the last year we have been influenced by El Nino," says Weingartner. "Whether or not that is occurring in conjunction with a regime shift, I don't know. Our Canadian colleagues noticed in the Gulf of Alaska that nutrients necessary for phytoplankton production were depleted from the surface lay
Contact: Doug Schneider
University of Alaska Fairbanks/NOAA Sea Grant Program