Understanding Movements of Steelhead in the Clearwater River Drainage

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