Michigan Department of Natural Resources
Fisheries Research Report No.1824, 1975
Population Dynamics of Wild Brown Trout inGamble Creek, Subject First to Angling,
then with no Angling
Howard Gowing
Abstract.-During an 8-year period between 1966 and 1973, a 0.76-mile section of Gamble Creek containing brown trout was closed to fishing. Density, age structure and other parameters of the population were monitored annually in the spring and fall. Similar data were available for this stream section for five consecutive years (1961-1965) prior to its closure to fishing. A compulsory creel census was conducted on 1.5 miles of Gamble Creek during 1961-1965. Population dynamics of brown trout were compared for these two periods. During 1961 - 1965 angling pressure was light, varying from 46 to 62 hours per acre; and the catch was small, ranging between 2.8 and 6.2 pounds per acre. Growth rate of brown trout did not change during the period of study. Average back-calculated lengths (total) for age-groups 0 through IV were 3.3, 6.5, 9.1, 11.3, and 12.7 inches, respectively. This represents comparatively slow growth. Survivorship curves from egg through age V were similar for the two experimental periods. During the period open to fishing, average total production was about 60 pounds per acre, of which anglers harvested about 4 pounds per acre. Average production was about 96 pounds per acre during the period when the stream was closed to fishing; during those years there were greater densities of both fingerlings and legal-size trout. Population data accumulated between 1947 and 1973 suggest that changes in fingerling and juvenile trout may be temporal and coincidental with closure to fishing. There is little evidence from the long history of fishing on Gamble Creek to indicate that closing the stream to fishing increased the density of legal-length trout. Trout movement into this stream section probably accounted for the increase. The population of brown trout is not generated completely within the study area, but rather is influenced by both internal and external factors.