Written by Will Lubenau, University of Idaho
Second year of research started this summer.
The second field season for the study has officially started. Tagging at Lower Granite Dam on the Snake River began on July 2, 2020. As of July 19th, 205 steelhead have already been tagged and released as part of this research to evaluate how many wild and hatchery steelhead are caught by anglers, and how often each year.
For the second field season, the goal is to tag a total of 2,000 steelhead; 1,000 adipose-intact fish and 1,000 adipose-clipped fish so obviously we are just getting started with our second season. Please examine all fish that you come across for a tag that located near the dorsal fin. To report a tagged fish, please go to https://idfg.idaho.gov/fish/tag/add. Remember, all reward tags must be returned to IDFG to claim the reward.
A steelhead is fitted with a tag while passing Lower Granite Dam. Data from anglers on tagged steelhead they catch is critical to understanding how often steelhead are caught while migrating through Idaho.
What did we learn so far in year 1?
We have been taking our first look at the data from the first season of the steelhead study and are learning some interesting things. As I always mention, the information discussed here is preliminary but provides a look at what we learned during our first season.For additional information on preliminary study results, you can read an article recently published in the Lewiston Tribune.
There are two primary objectives to this study., 1) estimate how many wild steelhead are caught in Idaho’s steelhead fisheries and 2) take a closer look at how well steelhead survive being caught and released. These are important to understand for Idaho’s steelhead fisheries since we manage for both hatchery fish harvest opportunity and wild fish recovery as part of the fishery structure.
Currently, IDFG uses hatchery fish to estimate how many wild fish are caught in the state. IDFG assumes hatchery and wild fish are encountered by anglers at an equal rate. For example, if based on IDFG surveys it is estimated that 40% of hatchery fish were encountered by anglers, then it is assumed that 40% of our wild fish were also encountered by anglers. This study was set up to test if that assumption was accurate.
We tagged 878 wild steelhead at Lower Granite Dam last year. Of the 878 fish, 200 were caught and reported by anglers. However, we recognize that some tags are caught and not reported so it is important to account for non-reporting in our estimates. Since some of the tags had rewards associated with them, we can use that to estimate how many tags were caught and not reported. By combining the tag reports with an estimate of how many tags were caught and not reported, we get an idea of how many wild fish were encountered.
An angler releases a double-tagged steelhead from the Clearwater River. Fish with 2 tags help biologists understand how many tags fall off and are lost. Understanding tag loss makes calculations on how often steelhead are caught more accurate.
The main findings so far.
In the first year of the study, the encounter rate for Idaho’s wild fish was about 35% while the hatchery fish encounter rate was about 40% to 45%. With wild steelhead conservation being a primary concern for IDFG, this is good news because it means the wild steelhead encounter rate estimated in the past may have been conservative.
To estimate survival of caught-and-released wild fish, we used detections from PIT tag arrays (click here to learn more), fish weirs (click here to learn more), and hatcheries to document survival of our study fish. About 65% of the wild fish reported as caught were detected after capture and known to have survived while about 62% of fish not reported as caught were detected and known to have survived. Preliminarily, the nearly equal rates of detection for fish reported as caught and fish not reported as caught suggest that catch-and-release angling has little influence on steelhead survival.
For more information on Wild salmon and steelhead click here.