Michigan Department of Conservation
Institute for Fisheries Research Report No.1745, 1968
Effects of the Rifle River Watershed Development Program on Trout Fishing
Howard Gowing
Abstract.-An extensive program of watershed and stream improvement was Initiated in the upper portion of the Rifle River watershed in July 1950 to restore and maintain a high quality of trout fishing in the Rifle River. In this report, comparisons are made between angling records for streams in the Rifle River Area obtained for 6 years prior to the improvement program (1945-1950) and 6 years thereafter (1956-1961). Angling records for the upper Rifle River (4.6 miles) during the pre-improvement period showed (1) an average fishing pressure of 185. 4 hours per acre, (2) a total catch of 3,972 wild trout (96% brown trout) for an average annual yield of 29.0 fish per acre, and (3) an angling quality of 0.16 fish per hour. On the other hand, the post-improvement period disclosed: (1) an average fishing pressure of 299.7 hours per acre, (2) a total catch of 5,214 wild trout (99% brown trout) for a mean annual yield of 38.1 fish per acre, and (3) an angling quality of 0.13 fish per hour. Comparisons of the salient features of the Rifle River fishery for both periods revealed: (1) the seasonal pattern of fishing pressure was nearly constant; (2) on the average, the cumulative percentage catch of wild trout each year showed little change; (3) no consistent change was observed in the total annual catches of wild brown trout during either period; (4) the length-frequency distribution of wild brown trout was similar for both periods and the mean length of fish was almost identical; and (5) observed differences between periods for both mean annual catch and angling quality were not significant statistically. A complicating factor in this evaluation was the 60% increase in fishing pressure on the Rifle River in 1956-1961 over that of the pre-improvement period. This uncontrolled variable made it difficult to assess the role of the watershed improvement work on the fishery. More wild trout were caught in the post-improvement period than previously but this increase was matched by the rise in fishing pressure and is reflected in the similarity of the average catches per hour for both periods. If angling pressure could have been held down at the previous level, changes in the fishery could well be ascribed to the watershed work. Since pressure could not be controlled, we have no conclusive evidence that the increase in catch of trout was due to the watershed program. The watersheds of two tributaries of the Rifle River that flow into the Rifle River Area also were included in the program. The interpretation of the fishing data for these streams (Houghton and Gamble creeks) also is obscured by annual fluctuations and rising fishing pressures. There was no significant change in mean angling quality on Gamble Creek but a pronounced drop (58%) for Houghton Creek in the post-improvement period. The average annual catch was identical in Houghton Creek for each period but fishing pressure increased by 135% in 1956-1961. There was some evidence that the trout population in the lower part of Gamble Creek increased following the installation of channel deflectors. The summer water temperature of the upper Rifle River was lowered by diverting the flow of Gamble Creek directly into the Rifle River via a diversion channel instead of through Devoe Lake.