(Stenodus leucicthyes) are the only predatory members of the whitefish
family and inhabit only arctic and subarctic drainages of Asia and North
America. They are found naturally in the large northerly flowing rivers
of Russia and in the Mackenzie and Anderson Rivers of Canada. In Alaska
they occur in the Kuskokwim, Yukon, Kobuk and Selawik rivers. Early
French explores in North America called it “inconnu”, which means “unknown
fish”, and this is an accepted common name.
Sheefish have a silvery streamlined body, large scales and a strong lower
jaw that projects past the upper jaw. Their general body form is much
like that of other successful predatory fish such as Tarpon and Snook.
Sheefish over winter in the lower reaches of rivers in or near estuaries
and undertake long migrations to faster flowing upper reaches of rivers to
spawn in the late autumn. Sheefish may migrate over 1,000 miles to reach
spawning areas in large rivers such as the Yukon. Females broadcast their
eggs at the surface of the water as fall weather reduces the water
temperature to near freezing. Males fertilize eggs from below as they
fall through the water column to lodge between stones in the streambed.
Mature Sheefish are very fecund, and a large female may release 400,000
or more eggs. Sheefish generally do not spawn each year after reaching
Young Sheefish emerge from the gravel in the spring and drift downstream
to rear in slow moving waters of lakes, sloughs or estuaries near the
mouth of the river. They feed on plankton during their first year, but
soon switch to a diet of fish and begin to grow rapidly. Sheefish may
reach sexual maturity at a weight of 7 to 9 pounds at 7 to 10 years of
age. Sheefish can spawn repeatedly over their life that may extend for
more than 30 years in the case of the largest individuals.
Females generally live longer and attain larger sizes than males. The
Kobuk River holds Alaska’s slowest growing, longest lived, and largest
Sheefish and here females may reach a weight of 50 pounds. The State of
Alaska angling record is a 53 pound Sheefish caught from the Kobuk River.
However, most of the fish in the spawning population are smaller and
anglers visiting this river should expect to catch fish averaging around
15 – 25 pounds. Fish over 30 pounds are considered large, and an angler
fishing for more than a day or two can expect to catch several of fish in
the 25 - 35 pound range.
In recent years, the Sheefish population in the Kobuk River appears to be
at or near record levels of abundance. It is likely that excellent
conditions for survival of young fish occurred during 1997-1999 and these
fish have recently recruited to the spawning population. Fishing has been
excellent during the past three years and will likely continue to be for
some years into the future as this group of fish moves through the
Our guide on the Kobuk has many years of experience on the river and is
very familiar with areas where Sheefish are seasonally abundant. Their
migration pattern puts fish in the upper river from late July through the
end of September. Sheefish tend to hold near the bottom is areas of
fairly swift current and moderate depth of 6 to 10 feet. Most fishing is
done from a boat anchored near the edge of the current, although it is
possible to fish from shore at a few locations. Come prepared for large
fish in swift currents. A 10 wt rod with a deep sinking shooting head or
integrated head line is recommended. For those skilled in the use of a
two handed rod, fishing from shore can be rewarding. Again, deep sinking
lines are required. Sheefish tend to strike at brightly colored attractor
patterns or baitfish imitations. Standard salt water baitfish flies such
as Clouser minnows and deceivers are very effective.
Kobuk River Sheefish offer one of the few situations were an angler can
expect to catch a large number of large fish in a remote river situation.
If water conditions are reasonable, an angler can expect to catch 20 or
more fish per day that will range from 7- 35 pounds, and there is always
that chance of a real monster. Moreover, the upper Kobuk River is one of
Alaska’s more scenic locations and other than an occasional local
subsistence user from Kobuk or Shungnak a visitor can expect to see few