Response of Wild Brook Trout to a No-Harvest Regulation in a Central Minnesota Stream

Due to concerns over a decreasing brook trout population possibly as a result of angler harvest, possession of brook trout was prohibited from Stoney Brook, Cass County, Minnesota, starting in 2006.  Harvest of sympatric brown trout continued under the statewide regulations and no additional tackle or bait restrictions were made.  Nearly annual electrofishing surveys of the trout population in four sections covering about one-half of the primary trout water from 1990 through 2011 have shown significant increases in brook trout reproduction and in adult brook trout size and abundance since the harvest restriction.  The estimated average population of yearling and older brook trout in 2009-2011 increased by over 500% to around 2,500 fish compared to the pre-regulation average population size of about 400 fish.  The wild brown trout average population decreased by about 30% in the same time period.  The number of brook trout equal to or greater than 254 mm in length captured in electrofishing surveys increased from a pre-regulation average of 16 fish per year to an average of 221 fish per year in 2008-2011.  The brook trout population in Stoney Brook was able to increase in the presence of competing brown trout when differentially protected from angling harvest.