Tag Team

A new research project could shed light on declining fish populations.

Last spring, in response to record-low populations of trout in the Big Hole, Beaverhead, Ruby, and Madison rivers, Montana Fish, Wildlife & Parks (FWP) and MSU researchers launched an intensive study to get to the bottom of it. Since 2011, rainbow and brown trout numbers have been decreasing on these rivers with dead and diseased fish being found in droves, drawing significant public interest and concern.

The new study revolves around tagging mature brown and rainbow trout to collect data on their health, movement, and overall population structures. Researchers use electrofishing to catch trout, then each one is weighed, measured, and pricked with a bright yellow or blue tag visible to anglers. A PIT tag—similar to a dog’s microchip—is also implanted into the fish’s muscle tissue, allowing researchers to later re-catch and scan the fish to track its movement and health. The trout are also visually inspected for any signs of infection or disease.

The tagging study relies on angler reporting to understand the impacts of catch-and-release mortality.

“The main intent is to compartmentalize mortality,” says Mike Duncan, a Fisheries Program Manager for FWP who’s helped organize and develop the study. “We can track individual fish through time, which will allow us to look at mortality and growth rates across these rivers and compare them to the environmental conditions, allowing us to tease apart environmental conditions and their effects.”

But environmental factors are only half the equation. The tagging study relies on angler reporting to understand the impacts of catch-and-release mortality. Results could be used to adjust management plans and fishing regulations, such as potentially limiting fishing to barbless or single hooks.

The researchers will likely need several more years of data to come to meaningful conclusions.

Voluntary angler reporting is critical to the project. “The thousands of anglers on these rivers are interacting with, holding, and seeing more fish than myself or FWP could ever hope to,” says Max Rubino, a Ph.D. student at MSU leading the project. “They really care a lot about the fish and the systems they’re interacting with.”

If you catch a tagged fish, says Rubino, clip the tag as close to the fish’s skin as possible, being careful to minimize handling time. Then go to FWP’s website to provide the tag number and basic information about the catch. Yellow tags are worth $100, and blue tags provide entry into a raffle for gear and fishing trips.

With anglers on the lookout, the study is moving ahead at full speed. Still, definitive results have been slow, and the researchers will likely need several more years of data to come to meaningful conclusions. Encouragingly, though, the prevalence of diseased fish in the surveys is at one percent or less, although the causes of most infections are still unknown.

For now, the best we can hope for are good snow years that allow for colder water temperatures all summer long, helping juvenile fish survive. As the old saying goes, pray for snow.

Tag-reporting resources can be found at mtcfru.org/msutag. For an informational video, and to stay up to date with press releases, interim study reports, and changing restrictions, visit fwp.mt.gov.