Along coastal regions in the Northwest Arctic, a staple fish may be expanding its habitat because of warming waters. That is a key finding from a two-year study that monitored sheefish movements using satellite transmitters.
“These ones here are generally considered to be the largest sheefish in the world,” said Kevin Fraley, a fisheries ecologist and lead on the study. “That's where the world record sheefish was caught on the Pah river, a tributary of the Kobuk River.”
Sheefish, or sii, are a whitefish that’s only found in the Northern Hemisphere. In the Northwest Arctic, their spawning grounds are along the upper Kobuk and Selawik rivers. In fact, the name “Selawik” comes from an Inupiaq word that means “place of sheefish.”
Fraley’s organization, the Wildlife Conservation Society, a global nonprofit research organization, has spent over a decade studying sheefish in the Northwest Arctic.
Fraley said the fish in the region are bigger than populations further south that spawn in the Yukon and Kuskokwim River. Sheefish populations in the Northwest Arctic have more food available, and they live longer in the colder waters. A single sheefish can measure 3 ½ feet and weigh 50 pounds — so one fish can provide several meals to a large family.
“They're so important for people out here in Kotzebue,” Fraley said. “People really rely on them especially during this time of year, for putting them in the freezer for really great, fresh, wild food.”
According to the new study, sheefish habitat could be expanding.
“The key findings are that the fish distribution seems to be broader now, north and south of Kotzebue Sound than it was in the past,” Fraley said.
According to Fraley, now sheefish can be found as far north as Point Hope and as far south as Shishmaref, a significant increase over what was previously thought to be their range. And there's a reason for it.
“We think basically climate change, global warming, where you have these longer summer seasons, where fish have more time to move up and down the coast before they overwinter in Hotham Inlet,” Fraley said. “So they just have more time to explore along the coast and check out these new habitats. ”
The study was funded through the Office of Subsistence Management in collaboration with the Native Village of Kotzebue and other researchers. Fraley’s organization, The Wilderness Society, also worked with the University of Alaska, Fairbanks, Alaska Department of Fish and Game, and the Selawik Wildlife Refuge.
Fraley said his team interviewed subsistence fishermen and reviewed literature on traditional ecological knowledge from the region.
They also looked at otoliths, or fish ear bones. The ear bones allowed them to determine the age of the fish as well as which rivers they came from. The Kobuk and Selawik Rivers each have unique chemical markers that can be found by studying the ear bones.
“It's a pretty crazy technique, but you can use a laser to shoot through into the otolith, you can actually tell if a fish has been in salt water, fresh water or brackish water during different points in its life.” Fraley said. “It's almost like forensic science, but with a fish.”
Fraley’s team also attached satellite tags to sheefish, which tracked their movements, water temperatures and the depths they swam at. Fraley said the study’s findings have implications for subsistence users in several communities.
“People that maybe historically didn't catch a lot of sheefish further north or to the south might start seeing more of them in their catches,” Fraley said. “So it's potentially a new resource for people.”
Besides sheefish’s expanding habitat, Fraley said data from the tagged satellite fish also showed that the fish were spending more time in very cold water below the sea ice and able to dive to up to 80 feet below the surface.
One of the tagged fish was able to overwinter in a lagoon at Cape Krusenstern National Monument, which Fraley says showed that sheefish could potentially survive in waters with low oxygen levels and limited amounts of unfrozen habitat.
Although the study is complete, Fraley says he hopes to do more sheefish studies in the future.
There are several satellite tags that have not been retrieved. Information on how to return the tags is written on the tag. The reward for returned tags is $100 and the cost of postage.
