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Cutthroats no homebodies

5/31/2006

Salmon and steelhead migrations are storied. But scientists have long reasoned that inland trout were homebodies, that they stayed put throughout life. Some of the research backed up the notion.

A study by Canadian trout biologists in the early 1990s showed that a great majority of cutthroats in a coastal stream moved less that 10 feet between spring and autumn. Other studies across the country on cutthroats, brook trout, and brown trout dating to the 1950s would leave me believing that inland trout never leave home.

Yet, other research on bull trout and rainbow trout shows they have a potential to make long tracks in short order. Some bull trout in Idaho moved 25 miles over a few months.

New research on Bonneville cutthroats in the Beaver River in Utah and Idaho may have you rethinking your "resident" cutthroat populations.

Using radio telemetry, researchers from Utah State University followed nine adult cutthroats over the course of an entire year. Individual fish were tracked at varying times to elucidate movement patterns over seasons and over the course of a day. Here's what they found.

Cutthroat results

In autumn and winter, the cutthroats stayed at home. Some fish moved a few feet, but by and large, they tended to roam very little. Given the time of year and seasonal conditions, that makes sense as fish would have to expend a lot of energy to move about and find limited food.

In spring, as the urge to procreate came on, the fish put it into high gear. Some cutthroats moved over four miles, essentially to find the right spawning habitat.

Movements during summer were much less, as the fish seemed to settle in for the warm months. Still, on average, the radioed fish tended to move about a half mile over the course of the season.

There was no predictable directional movement by season. For example, some fish in every season moved upstream and some moved downstream.

As for daily movement, the researchers followed fish for a 24-hour period in September. All fish moved on average six times in a day, moving up to 850 feet a time. The habitats were as different as daylight and dark.

In the nighttime, the cutthroats keyed into low-velocity waters where they used very little energy staying put while resting. In the daytime hours, they moved to high-velocity waters to hold position in-wait for drifting food. Most movement took place at dusk and dawn; the least occurred at night.

This research certainly gives biologists a better handle on cutthroat population dynamics. As for fishing, if you've got a hot spot that goes cold, maybe it's not that the fish stopped feeding — maybe they moved on.