Adopt-A-Fish update – May 8, 2008
provide some critical data
By MATT JAEGER
Montana Fish, Wildlife and Parks
GLENDIVE – Over the past few years, more and more anglers have enjoyed the great fishing opportunities that the lower Yellowstone River provides. Some anglers may have even had a fish featured in the Missouri-Yellowstone Adopt-a-Fish Program on the end of their line.
But whether or not they are caught by anglers, movements of fish in the Adopt-a-Fish program are one of the pieces of information that biologists use to learn about the effects of increased fishing pressure on the fish populations that call the lower Yellowstone home.
Sauger are both one of the most prized fish by anglers and one of the most interesting movers in the Adopt-a-Fish program. Over the past few years, we’ve learned that radio-tagged sauger can migrate long distances between spring spawning areas and home areas where they spend the rest of the year. In fact, some sauger move over 400 miles between spawning and home areas each year.
Although learning where sauger are distributed is important, biologists are equally interested in how sauger are distributed relative to one another. From our radio-tagged fish, we’ve learned that sauger are spread out over a very large area during much of the year but tend to group up and form aggregations in smaller areas during spawning periods.
Forming aggregations is an effective strategy to improve spawning success in a big river like the Yellowstone but it also makes sauger very susceptible to anglers during these times.
This increased use by anglers and aggregation behavior of sauger can combine to create an opportunity for overharvest and cause large declines in the population.
To determine whether overharvest is occurring, especially during times of aggregation, biologists rely on three key pieces of information: 1) population trends from our annual monitoring surveys, 2) age distribution of the population, and 3) angler return of tag information when they catch a sauger marked with a yellow spaghetti tag.
Population trends help us track increases and declines through time to give us a feel for how many sauger are out there. Age distribution gives us an understanding of how long the sauger that are out there are surviving. If survival is high we expect to see a stable or increasing trend and a fair number of older, larger fish. If survival is low we expect a declining trend and a population made up of smaller, younger fish.
However, biologists are able to learn the most about how the sauger population is doing when anglers return information from the tagged fish they catch. This information helps us determine how many sauger survive each year, how many sauger die from natural causes like predation, how many sauger are caught, and how many of the sauger that are caught are being harvested. It also helps us determine how many sauger are being harvested when they are aggregated compared to when they are more widely distributed.
Because this information is so important, anglers should be sure to report the tag numbers, size of the fish, where it was caught, and whether it was kept or released to the biologists at Montana Fish, Wildlife & Parks whenever they catch a tagged fish. Tag information can be returned by calling 406-234-0900.
So far, we’ve learned that anglers are catching almost 30 percent of the sauger that we tag each year, which is enough to cause population declines. However, only about half of these fish are being harvested and more sauger are being caught and harvested during late summer and autumn when they are widely distributed than in spring when they are aggregated and most susceptible to overharvest.
Because anglers are releasing many of the sauger that they catch, especially older, larger females caught in spring, Yellowstone River sauger are still in good shape even though there are more people fishing for them.
Gaining this critical information would not be possible without the combined help of sauger fishermen and the radio-tagged fish in the Adopt-a-Fish program.
Weekly updates on our radio-implanted fish can be found on the Missouri-Yellowstone Adopt-A-Fish home page with updates posted Thursday mornings in April and May. Just click on the Find your Fish button on the home page. The program is sponsored by Montana Fish, Wildlife and Parks, The Billings Gazette, Walleyes Forever, Montana PikeMasters, U.S. Army Corps of Engineers, U.S. Geological Survey, Bureau of Reclamation and the U.S. Fish and Wildlife Service. The program is free.
School classrooms, youth fishing clubs and home schoolers can sign up for the program and adopt and name two fish. Just go to the Web site and click on the How To Adopt Button or send us an e-mail at Missouri-Yellowstone Adopt-A-Fish.
Adopt-A-Fish correspondents are fisheries biologists with Montana Fish, Wildlife and Parks. They’ll post weekly updates every Thursday throughout April and May on this site and in the Outdoors section of The Billings Gazette.