Michigan Department of Natural Resources
Fisheries Research Report No.1840, 1976

Trout Production and Catch Under Normal and Special Angling Regulations in the North Branch of the Au Sable River, Michigan


Gaylord R. Alexander and James R. Ryckman


      Abstract.-The annual production of wild brook and brown trout from the normal regulation water (7. 0-inch minimum size limit, 10 trout creel limit, any lure permitted) of the North Branch of the Au Sable River was 102 kg/ha compared to 83 kg/ha from the special regulation water (9. 0-inch minimum size, 5 trout creel limit, artificial flies only). Brook trout made up about half the production in both waters. Overall production was similar to that found in other mid-western streams.

Over 80% of the trout production was accrued during the spring to fall period for both species. Most of the annual production was contributed by the younger fish in the population.

The turnover ratio was 1.88 for brook trout and 1.19 for brown trout in the normal waters and 1.87 and 1.43, respectively, for these species in the special waters.

Angler harvest of the annual production in the normal waters amounted to 35% of the brook trout and 39% of the brown trout. By contrast, a mere 4% of the brook trout and 15% of the brown trout production was cropped from the special waters.

If the management objective is to maximize the harvest of trout, normal regulations are far superior.