Sheefish study finds healthy spawners on Selawik River
Scientists congregated at the Selawik River sheefish spawning grounds this fall to continue a three-year study of the Arctic fish.
One of the reasons for the ongoing study is to establish whether or not the "permafrost thaw slump" in 2004, which happened 40 miles upriver from the spawning grounds and turned the usually-clear river water turbid and silty, has affected the population.
Did those fertilized fish eggs result in healthy sheefish? Or did the numbers drop off after the slump?
Biologists from the U.S. Fish and Wildlife Service harvested male sheefish at the spawning grounds and removed the ear bones to decipher the age of the fish. Sheefish can easily live 30 or more years, and they don't hit maturity until around age 9, and thus wouldn't swim upriver to spawn unless they were of age. By determining the ages of the fish, biologists will be able to tell whether those eggs thrived or perished in the murky aftermath of the permafrost event nearly a decade ago.
The reason the fish are being studied at the spawning grounds is to ensure that they are in fact Selawik-River sheefish and not tourists from other water bodies.
Biologists are also plucking Kobuk-River sheefish (bycatch from the chum-salmon test fishery near Kiana) to use as a control group.
If the findings from both rivers are the same, it would indicate no significant impact on the Selawik fish from the 2004 event.
"From those eggs that hatched in 2004, we are just now seeing those fish," said Ray Hander, a fisheries biologist with the U.S. Fish and Wildlife Service. Hander has been with fish and wildlife for 10 years and has worked on this project since its inception.
"The population is made up of mostly older fish," Hander said. "With the bulk of the population being older, we expect a large number of fish to enter the spawning population. If that occurs on the Selawik and Kobuk then the slump didn't have a large impact.
"We can't tell at this time yet if the slump has affected the population."
The 200 sheefish that were used for data collection were given to Selawik and the meat was dispersed throughout the community, Hander said, adding that they had a drying rack set up at their river camp to hang the fish until locals came to get it.
The second part of the project is data collection relating to population numbers of spawning sheefish on the Selawik. Sonar was set up in the river to count fish as they made their way downstream after spawning to their winter home in Selawik Lake and Hotham Inlet.
In the past, the sonar-aspect of the fall project has been cut short due to river ice forming, but this year with unseasonably mild temperatures, biologists were able to finish up the count.
"We were able to catch the whole run," said Hander. "This might be the only opportunity to see the whole run go by instead of being forced out by ice."
Scientists counted approximately 25,000 sheefish this year, up from last year's 16,000 and the 2011 count of 21,000, though all those numbers are preliminary, said Hander.
Most fish were counted during the night, according the Selawik National Wildlife Refuge, which posted updates from the study on its Facebook page.
"Biologists already knew, as elders do, that sheefish turn around and head downstream quickly after spawning," read an update from the refuge.
In just three days, about 65 percent of the sheefish spawners had passed by the sonar.
The U.S. Fish and Wildlife Service project is funded by the Office of Subsistence Management and in collaboration with Native Village of Selawik and the Alaska Department of Fish and Game.