The number of sheefish on the Kobuk and Selawik rivers is healthy, as are the fish themselves, scientists are reporting.
Each fall, biologists from the Alaska Department of Fish and Game and the U.S. Fish and Wildlife Service gather on the Kobuk and Selawik rivers to study the popular subsistence species during spawning. The studies look mostly at the population of spawning fish, along with the overall health.
Sheefish don't necessarily spawn every year. And females don't start spawning until they're 8 or 9 years old, while males don't start until they're around 7. Scientists use radio tags and sonar to keep track of, and count, the giant fish.
Sheefish studying and counting by Fish and Game dates back to the late '60s, said fish biologist James Savereide.
"This started a long time ago but as time progressed and the fisheries, which were always an important resource for subsistence users, saw more sport-fishing pressure, Fish and Game felt they needed a gauge on the population through regular research," he said.
In the mid-'90s, biologists started tagging fish, then recapturing them a week or so later and counting how many tagged fish were caught as a way to estimate the overall population.
On the Selawik last year, more than 20,000 spawning fish were counted, while on the Kobuk River, upwards of 40,000 have been noted passing through. And those are just the fish that are spawning.
"The stocks themselves, those two numbers added together plus all the fish that didn't spawn, are good," he said.
Radio tags were brought into the mix in the 2000s, while most recently sonar has been adopted as a tool to count fish. And fish collected for tagging look big and healthy.
"In all the years I've been on the Kobuk River … I've never sampled or seen what I would deem an unhealthy fish," said Savereide.
Meanwhile, U.S. Fish and Wildlife biologists on the Selawik River have been tracking the age of sheefish in that area and are in the midst of an ongoing study that tracks the potential effects on the population after a 2004 permafrost slump dumped sediment into the river about 40 miles upstream of the spawning grounds.
Male sheefish were harvested last year at the spawning grounds and scientists removed the ear bones to decipher the age of the fish. 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 a decade ago.
Unlike last year, however, this season's study was cut short due to an early freeze-up, said Bill Carter, the fish biologist at the Selawik National Wildlife Refuge.
Now that the data collecting from the spawning fish is done for another year, biologists are busy entering their findings.
In the winter, fish from both the Selawik River and Kobuk River stocks congregate in Kobuk Lake, Savereide said. Research gathered from a team at the University of Alaska Fairbanks that used acoustic tags found that the two groups intermix over the winter before splitting off and venturing up their home rivers. They spend much of the winter in the northern parts of the lake.
"Sheefish are so important as a subsistence resource that we will be visiting these rivers every two or three years to see if the numbers are still good," he said. "We don't see any large concerns as far as stock declining at this time."
The sonar equipment used by the state agency was paid for by the state's Roads to Resources initiative as part of environmental research on the proposed road to the Ambler Mining District.
"They're giving us money to see if we can come up with efficient ways to estimate sheefish running in and out of there in order to determine if a road would affect those stocks, " said Savereide.
"The whole goal is to maintain these stocks at the level they're at now or better to ensure the number of sheefish that people harvest never goes down. We would like to see them harvest more if they wanted to but they don't because they're getting plenty. That whole reason is just to make sure the subsistence users have enough fish to survive."
This story first appeared in The Arctic Sounder and is republished here with permission.