Michigan Department of Natural Resources
Fisheries Research Report No. 1997, 1993.

Comparative Catchability, Growth, and Survival
of Two Wild Stocks of Brown Trout


Gaylord R. Alexander and Andrew J. Nuhfer

Hunt Creek Fisheries Research Station
Route #2, Box 2299
Lewiston, Michigan 49756


Abstract.-The catchability and genetic growth potential of trout may be changed, over time, by differential angler harvest of more catchable and faster-growing fish from each cohort. To test this hypothesis, yearling brown trout Salmo trutta from the Au Sable River and Gilchrist Creek were stocked into Fuller Pond. Brown trout populations from the Au Sable River were believed to have been historically exploited more intensively than those in Gilchrist Creek. We compared their vulnerability to capture by angling, relative growth, and survival over a 2.5 year period. Using artificial flies and lures, Gilchrist fish were approximately four times easier to catch at age 2, and three times easier to catch at age 3 than Au Sable fish. Vulnerability to angling was not correlated with growth rates, as few significant differences occurred in growth. There was also no difference in survival of the two strains during the study period. Differential angler exploitation over time may have altered catchability of these wild trout stocks. Other factors that could account for observed differences in catchability include genetic dissimilarity of founder stocks, genetic differences due to differences in natural selection between the rivers, or unknown factors. By selection of appropriate brood stocks, fishery managers could double or quadruple brown trout catch rates for some catch-and-release fisheries that are established or maintained by stocking. Conversely, managers could reduce angler exploitation rate, thus permitting trout to grow for a greater length of time in harvested fisheries, by stocking strains that are less catchable.