Michigan Department of Natural Resources
Fisheries Research Report No. 1868, 1979
A History and Evaluation of Regulations for Brook and Brown Trout
in Michigan Streams
Richard D. Clark, Jr., Gaylord R. Alexander, and Howard Gowing
Abstract-Since the establishment of the Board of Fish Commissioners in 1873, the trend
in Michigan trout fishing regulations has been toward more restrictive and complex laws. Major
scientific investigations concerning the effectiveness of various types of regulations began
in 1945. They determined that a minimum size limit was the most effective regulation for controlling
exploitation of trout.
In this study minimum size limits for brook and brown trout in Michigan streams were evaluated
through mathematical modeling. Minimum size limits ranging from 152 to 229 mm (6 to 9 inches)
were tested for brook trout and from 152 to 305 mm (6 to 12 inches) for brown trout. Catch-and-release (no-kill) regulations were also simulated for both species. Maximum yield in numbers
and weight of trout harvested was obtained at a 152-mm (6-inch) minimum limit for both brooks
and browns. Yield in numbers and weight of trout caught and released increased as size limit
increased and was maximum with a no-kill regulation. Total yield (defined as weight of trout caught
and harvested plus weight of trout caught and released) increased as size limit increased and was
maximum with a no-kill regulation. As size limit increased, the number of larger trout harvested
increased, but at the same time, total number of trout harvested declined.