This is a special guest post by:
Joe DuPont
Clearwater Region Fishery Manager
Idaho Department of Fish and Game
Have you been
noticing a truck with a giant antenna in the bed cruising up and down the
Clearwater? Maybe you were fishing and
saw a jet boat running the river with the same antenna? You were probably wondering what that was
about. Idaho Department of Fish and Game,
in collaboration with Nez Perce Tribal Fisheries Research Division, has been
tracking steelhead bound for the South Fork Clearwater River since September
with the primary objective of trying to better understand how steelhead move
and use the river system and what causes them to move. It will be especially be important for us to
learn how wild steelhead move through the river differently than the hatchery
fish we are targeting in our fisheries.
We
have been capturing South Fork Clearwater River bound steelhead since September
at a trap in the fish ladder of Lower Granite Dam. This trap has a system that reads PIT tags
(microchips implanted in fish to track their movement throughout the Columbia)
and was programed to capture any fish that were previously tagged as juveniles in
the South Fork Clearwater River. Once
one of these fish is captured, our staff inserts a radio tag down its throat so
it rests in their stomach (these fish generally aren’t eating after they leave
salt water). You can tell when you catch
one of these fish because it will have an antenna (basically a wire) sticking
out of its mouth. Each radio tag has a
specific code, which we can read using our receiver. That means we can track the movements of
individual fish and compare and contrast those movements to other fish.
We are in the
midst of what is just our first field season, but we have already started to
notice some interesting patterns. First,
the reservoir and slack water near the confluence seem to be an important
habitat for some groups of fish that are spending most of the winter holed up
and waiting for spawning season. On the
other hand, a smaller group of fish moved very rapidly, making the trip from
Lower Granite Dam to waters upstream of Orofino in a matter four or five days. Of course, many of the fish have been slowly
working their way up river, and some have found their way into your creels. Do some hatchery release groups move at different
times? Do they move together? When do most of the wild steelhead make big
upstream movements? These are the
questions we hope to address with this study.
Understanding the cues that cause some fish to move and others to stay
in the reservoir will help us better manage our fisheries.
The figure below depicts how far four of
our radio tagged steelhead had moved up from the confluence of the Clearwater
with the Snake River (distance on the vertical axis) by a certain time (date on
the horizontal axis). These are four
interesting fish that show some of the breadth for information we can obtain
using radio telemetry. For example, the
fish with Code 18 was one of our fastest migrating fish, but then it was
harvested near Greer in November.
Alternatively, the fish with Code 11 stayed in the confluence for weeks
before migrating, but now it is sitting below Dworshak Dam on the North Fork,
even though it should be heading for the South Fork! Our biggest challenge will be to find the
overarching patterns in this information that help us be better fishery
managers.
Why do we
need to know how steelhead move through the system to better manage steelhead
fisheries? Take the 2013-2014 steelhead
run as an example. Based on the poor
returns of b-run hatchery steelhead over Lower Granite Dam and into the
Clearwater River, IDFG instituted a one fish bag limit, with no harvest on fish
over 28 inches in the Clearwater River below Orofino Bridge and in the North
Fork. This management action was taken
in order to ensure that enough large steelhead returned to the hatchery to
comprise the broodstock for the next generation. In the future, understanding movement
patterns in the Clearwater may give us more options and more flexibility to
structure fisheries in other ways, which may be less restrictive. It may give us opportunities to structure
fisheries to protect wild fish in years where those runs are lean and hatchery
fish in years where we might not get enough broodstock. In short, we are collecting these data so
that we can learn how to best balance good fishing with good stewardship of our
limited steelhead resources.
So the next time you are on the river and see us
tracking fish, you will know what we are up to.
We are more than happy to answer questions about this program if we
happen to bump into you at one of the ramps or pullouts up and down the
river. Best of luck with spring
steelheading!Text and Photos By:
Joe DuPont
Clearwater Region Fishery Manager
Idaho Department of Fish and Game