In a new study, scientists have linked warming Arctic temperatures, changing wind patterns and shifting currents to movement of commercially valuable Alaska pollock in the Bering Sea.
The Bering Sea has seen the loss of a summer cold water barrier in recent years, which used to keep pollock from spreading out and moving north.
But while scientists are seeing drastic shifts in pollock movement patterns, further research needs to be conducted to know what the changes mean for communities like Unalaska and Dutch Harbor and the billion-dollar pollock industry.
“This research is really critical because pollock are a key ecological component of the Bering Sea shelf food web supporting the largest commercial fishery in the U.S. by biomass,” said Robert Foy, NOAA’s Alaska Fisheries Science Center director. “To get an accurate assessment of pollock abundance so that resource managers can set sustainable catch limits, we have to be able to understand pollock distribution, which certainly looks different under a warm water regime.”
While the implications of changing pollock distributions in the Bering Sea are not yet known, this study marks the first time American and Russian scientists have been able to work together to look at why the groundfish species has shown up in new places in recent years.
By looking at historical and recent data, they’ve been able to confirm both a northward shift of the species and a long-suspected movement of fish between U.S. and Russian waters.
“We were trying to compare what was driving those changes,” said Lisa Eisner, a NOAA Fisheries oceanographer and lead author of the study. “And also if it was possible for some of the fish from the eastern shelf to mix with the fish on the western side of the Bering Sea.”
While scientists have been surveying Bering Sea fisheries for nearly four decades, Eisner said this specific study was born out of the unusual warming events they’ve seen in recent years, and it also drew on historical datasets from both the U.S. and Russia.
According to Stan Kotwicki, program manager for NOAA’s Groundfish Assessment Program, pollock generally have a north-south migration. Typically, as ice comes down from the Arctic over the course of the winter, it pushes fish south to feed in warmer areas.
“And, of course, then during the spring, summer and fall, when the ice is melting, pollock move back north,” he said.