Brook Trout holding their own in St. Croix tributaries

Recent surveys of two tiny creeks flowing into the river found the native fish still swimming in the streams despite challenges.

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Deb Vermeersch is Assistant Area Fisheries Supervisor with the Minnesota DNR Hinckley Area Fisheries Office. This article was originally published in the office’s newsletter and is reprinted with permission.

A brook trout swims in a St. Croix River spring creek. (Greg Seitz, St. Croix 360)

The rocky bluffs surrounding the St. Croix River south of Taylors Falls hold a well-kept secret. Numerous cold springs arise from the steep hillsides. If the flow is sufficient, the streams that emerge from the springs can support Brook Trout.

The origin of these trout are somewhat of a mystery; there are no records of stocking, although in the late 1800s and early 1900s stocking records were not always kept. It is possible that these fish may be native to the St. Croix valley.

Hinckley Fisheries crews sampled two streams in August 2019 near the Osceola landing on the St. Croix River. Known only by their numbers, M-50-26 and M-50-27, these streams were designated as trout streams around 2000 after surveys in 1999 found Brook Trout.

A tiny trout stream tributary to the St. Croix River. (Greg Seitz, St. Croix 360)

Because these streams are so small, sampling is done with a backpack electrofishing unit.

The good news: Brook Trout were still present in both streams. M-50-27 had the most, with 26 adult and 12 young of year sampled in approximately 2500 feet of stream. The adults were not trophy sized by any means— lengths ranged from 3.3-5.5 inches.

In order for adult Brook Trout to grow to larger sizes, a stream needs to have plenty of deep pool habitat. M-50-27 has mostly shallow pools and riffles along its short course, which is not ideal habitat for big trout.

Brook trout in a St. Croix tributary. (Greg Seitz, St. Croix 360)

The bad news: M-50-26 has been altered by beaver activity over the years, making it extremely difficult to sample. Only one brook trout was caught in the approximately 1700 feet of stream that was walkable.

It is likely that more trout are in the stream, well protected from intrusive fish specialists and their electric wands. But beavers generally have negative impacts on trout waters in Minnesota. Beaver dams can block fish passage, and the pools they create cause fine sediments and debris to build up on the bottom.

Brook Trout need clean gravel stream beds for spawning. Beaver dams may also cause water temperatures to increase in the pools and immediately downstream: Brook Trout cannot survive in water that is above 65 degrees for extended periods.

Map showing Minnesota designated trout streams along the St. Croix River from Franconia to Osceola (MN DNR)

If you are up for an adventure with the prospect of small trout, these streams can be accessed by boat from the Osceola landing. Locations are shown on the southern Minnesota trout stream maps on the DNR website.

The lower portions of the streams are within the St. Croix National Scenic Riverway, but the upper reaches flow through private land.

One caution: These streams are extremely difficult to find! One day our crew sampled what they thought was one of the streams, only to find that the stream abruptly ended in a steep ravine much sooner than it was supposed to. A check of GPS points indicated that it was indeed the wrong stream! Amazingly, they did catch a few trout.


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One response to “Brook Trout holding their own in St. Croix tributaries”

  1. Mark Hove Avatar
    Mark Hove

    Love those little Brook Trout!

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Brook Trout holding their own in St. Croix tributaries