Selawik Refuge staff Nate Olson and Frank Berry surgically implant a radio transmitter in a sheefish from the Tagragvik River. September 2007.

Iñupiaq elders in northwest Alaska have long known that sheefish (Stenodus leucichthys) aren’t found in the Tagragvik River, a major tributary of the Selawik River.  So the Selawik Refuge staff was surprised to learn last year that sport fishermen were catching them there.  To investigate this further, Selawik Refuge biologists teamed up this fall with fisheries biologists from the Fairbanks Fish and Wildlife Field Office to float the Tagragvik River in late August and early September, fishing every deep hole along the way to see what they could find.

For the first few days, the crew caught no sheefish.  They finally hooked into one several miles downriver and from then on caught sheefish with every cast.  Many were in spawning condition.  “I didn’t expect to actually catch very many sheefish,” said Refuge biologist Nate Olson, “and definitely not the abundance of fish in spawning condition.” 

The crew surgically implanted coded radio transmitters in 30 of the sheefish.  The transmitters are expected to last at least five years.  Annual radio telemetry flights will give Refuge staff insight into the periodicity, timing, and locations of sheefish spawning.  Genetic samples and otoliths (to determine age) were also collected from sheefish.

The reasons for the abundance of sheefish in the Tagragvik River are not clear.  Iñupiaq residents of Selawik, about 40 air miles downstream, have used the Tagragvik River for subsistence activities for a very long time, and no one can recall ever seeing or catching sheefish in the shallow, gravel-bottomed river.  Recent research on sheefish in the nearby Selawik River revealed an astonishing growth (4 to 9 times) in this fish’s spawning population since the mid-1990s.  This growth may be propelling sheefish into areas they only rarely used before.  Another possibility is that a large landslide in 2004 in the upper Selawik River—which continues to muddy the river—may be spurring sheefish to seek new spawning areas.

Continued research will hopefully shed light on these questions.  “It is very exciting to be monitoring an event like this at its beginning,” said Olson.