Life on a Brook Trout Stream

[hookncook]

Whoever said pimpin’ ‘aint easy hit the nail on the head when it comes to the life of a brook trout.

Brook trout are constantly in a stressed environment. According to John Hoxmeier of the Minnesota Department of Natural Resources “we don’t have an unstressed Brook Trout population anywhere.”

Brook Trout are fished for, predated on, and have to compete for food and resting places with the invasive Brown Trout, and then’s as if their day isn’t getting any better toss in recent outbreaks of gill lice.

Recently, Hoxmeier did extensive research on Brook Trout in Minnesota trout streams. He found that Brown Trout tend to displace Brook Trout from feeding and resting areas; Brook Trout tend to gather in head waters, with Brown Trout in the base waters. He also assessed that Brook Trout live an average life span of two to four years.

At age 0, Brook Trout survive 2% better in Brook Trout dominated regions and streams. The trout tend to disperse away from fellow hatchlings. At age 1 survival is more seasonal based and they move upstream. At age two (and older), the trout tend to move away from Brown Trout.

Movement through out the year is based on water temperatures, as the seasons have an impact on water temperatures. In the winter: head and base waters tend to be cooler, and the mid waters are warmer. This is a result of the cold air temperatures on the base and head waters , and geo thermal heat keeping the spring fed mid waters warm. During the summer: the head and base waters are warmer, with the mid waters being cooler. This is a result of the warm air warming up the base and head waters, and the cold springs keeping the mid waters cooler.

When Hoxmeier’s crew studied Brook Trout populations before the removal of Brown Trout, and then Brook Trout Populations after Brown Trout removal. The numbers nearly doubled. Brook Trout populations prior to Brown Trout removal was 180/ mile. After Brown Trout removal, Brook Trout populations increased to 300/ mile.

Hoxmeier noted the difficult it was to keep Brown Trout out of a stream. His crew put up a barricade to prevent the Browns from swimming up stream, but noticed they had a tendency to want to jump the barricade. He also contributed the successful disbursement of Brown Trout due to flooding and the Browns ability to swim up stream and over the barricade.

Hoxmeier’s and crew also noticed gill lice in about 41% of the trout researched. Hoxmeier explained that there is no documentation that gill lice have no effect on the growth or survival of Brook Trout. He personally has not noticed any evidence of decreased growth or abundance between Brook Trout populations with or without gill lice in Southeastern Minnesota.

I have been seeing gill lice show up in populations that haven’t had it in the past. He suspects that there has to be a negative effect of gill lice on brook trout, he hasn’t found it yet. Hoxmeier believes that under stressful conditions (warm water, poor habitat, competition with brown trout), gill lice can have negative effects on brook trout performance. Hoxmeier plans on looking into gill lice further down the road.