Preliminary surveys point to Yukon River Chinook salmon in trouble
Scientists are continuing to find sea life traveling north into warming Arctic waters. Record water temperatures are affecting fish distribution and viability in the Bering Sea. Jim Murphy is the lead research biologist involved in a Northern Bering Sea surface and medium water survey launched from the NOAA operated research vessel Northwest Explorer, which tied up at the Port of Nome causeway Sept. 8. The survey has been ongoing since 2002.
“A lot of the focus that brought us up here at the beginning was to improve our understanding of the salmon populations in the Bering Sea,” Murphy explained in a dockside interview. Preliminary results of the first part of the survey show not a lot of juvenile chinooks coming out of the Yukon River.
“Catches of juvenile chinook salmon have been quite low during Leg 1 of the survey,” Murphy said in a report to NOAA colleagues. “We will know if this is a low abundance year once the survey is complete, but it is looking like it will end up being a low abundance year for juvenile Chinook.”
The survey is going down about 20 to 22 meters, but that is like the entire water column in shallow parts of the northeastern Bering Sea.
The Chinook has been a big concern. For now, Murphy was able to report high production of pink salmon and good numbers of coho and chum salmon, but very low numbers of Chinooks, or “kings.”
The Bering Sea produces 40 percent of the catch of fish and shell fish by weight with an off-the-ship worth of over a billion dollars. The waters provide three-fourths of the sustainable harvest used by people living along the coast for thousands of years.
Murphy provides research tools and production models for salmon that he uses to forecast for harvest managers and stakeholders—commercial and food gatherers—what future returns will be. He can forecast what future runs will be three or four years into the future, he said. The team aboard the Northwest Explorer included sea bird and marine mammal observers.
The team is attempting to sort out whether the problems with the Chinook production or issues surrounding their production is in fresh water or marine (salt) water. They have been doing work at the Yukon River delta to check the number of smolts coming out of the river.
“That’s what you have to do to separate out the fresh water as a factor,” according to Murphy.
“Fresh water is warming up and almost as dramatically as the Bering Sea. The spawners are coming back to heat stress of the river. “The fresh water is starting to reach their thermal limits,” Murphy said. Or it could be nutrition, but the fitness of the Chinook is not declining, so “if they’re losing their prey, they are able to find alternative prey.”
A preferred prey is capelin, the small oily fish valued by gulls and food gatherers in the Norton Sound area, gone missing in the past several years. “We did see some larval capelin, so we know there’s some spawning somewhere, but there’s just not the biomass you typically see,” Murphy said. The chinook are switching over to sand lance or needle fish.
The Chinook surveys are preliminary, but what scientists do know is that the Bering Sea is in one of the fastest warming parts of the world. Fish stocks have become increasingly vulnerable to marine heat waves, record surface temperatures, the loss of sea ice, warm low-oxygen waters, harmful algal blooms and disruption of food webs and conditions that stress the ecosystems.
“The Bering Sea is an Arctic system, but with this warm water, it’s becoming sub-Arctic,” he said. “ It’s becoming much more similar to what you would typically see in Bristol Bay or Southern Bering Sea, and that is going to change a lot of things.”
He has studied salmon his whole career, according to Murphy. A lot of research has to do with subsistence.
“I have been able to take the science and the research that I do and make it meaningful to the communities up the river,” he said. “Usually the science gets completely separated from the people.”
However, Murphy said, “the commercial fisheries do connect to the livelihood of people. It’s just education. The more you know about what’s causing changes in production of natural resources, the more you can make decisions that are consistent and scientific, instead of having them be political decisions,” Murphy concluded.
Murphy’s base is Alaska Fisheries Science Center at the Auk Bay laboratory in Juneau.
The survey is currently part of the Arctic Integrated Ecosystem Research Program and its partners.