Abstract.-We monitored the brook trout Salvelinus fontinalis population in a 2-mile section of Hunt Creek, Michigan, for 44 continuous years. In the first 17 years (1949-65), the population was subjected to fishing. In the last 27 years (1966-92) all fishing was prohibited. We conducted a complete creel census from 1949 through 1965 and trout abundance estimates every fall from 1949-92 and every spring from 1959-93. Our primary objective in this study was to compare brook trout population characteristics between periods of fishing and no fishing. Angler harvest of brook trout dramatically decreased the abundance and survival of legal-sized fish in Hunt Creek. Because fish were heavily cropped when they grew to a legal length survival of all age classes older than age 1 was significantly lower when the population was subject to fishing and harvest. Conversely, annual survival of trout from age 0 to age 1 was significantly higher during the harvest period. A complete creel census of trout catch during the fishing period showed that lower fall stock sizes and survival rates (spring to fall) observed were attributable to angler harvest. Fall brook trout populations of legal-sized fish were 127% higher when not cropped. However, about half of the increase in fall standing crop that was stockpiled by September during fishing closure was lost to natural mortality before the following April. Thus, the mean stock of legal-sized fish was only 65% higher by spring. Trout growth during 27 years when the stream was closed to fishing was not significantly slower than during 17 years with fishing in spite of an increase in total fall standing crop of about 25%. Only young-of-the-year trout in one stream section were found to be significantly smaller during the fishing closure. Populations of sublegal fish were not significantly affected by fishing and hence they reflected the range in natural variation that might be expected in a trout stream with a stable flow regime. During the 44-year study period the largest fall population of sublegal fish in the entire study area was 1.9 times the smallest population, while the highest spring population was 2.2 times higher than the lowest. The fall brook trout population in the least perturbed upper 1-mile of the study reach exhibited a significant increasing trend in abundance over the 44-year period. This suggested that environmental conditions may have improved for brook trout in Hunt Creek, and possibly other northern Michigan trout streams, over the past half century when development activities have been minimal. Conversely, fall populations of sublegal trout declined significantly over time in the lower 1-mile of the study reach where habitat quality was degraded by an experimental addition of sediment during 1971-76. This suggests that the adverse effects of bedload sediment have persisted in this stable-flow stream for approximately 20 years.
Our findings suggest that fishing regulations that reduce angling mortality of intensively-fished brook trout in small streams should significantly enhance populations of larger trout and improve the total catch of trout by anglers.