Relations between Angler Harvest, Effort, and Abundance of Fishes in Escanaba Lake, Wisconsin
Gauthier, Kevin J., Sr.
University of Wisconsin-Stevens Point, College of Natural Resources
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Measures of angler effort, harvest, and fish abundance are valuable indices for assessing management regulations, denoting species interactions, evaluating density-dependent factors regulating fish populations, tracking angler preferences, and monitoring sport fish populations as sport fisheries vary in time. In spite of the wide use of these metrics in assessing fish populations, their direct relations are not well understood. The objectives of this study were to: 1) assess how the annual angler harvest, effort, and abundance for sport fish has changed from 1946-1999 in Escanaba Lake, Wisconsin 2) determine relations between annual sport angler harvest and effort from 1946-1999 in Escanaba Lake, Wisconsin and 3) determine whether sport fish abundance could indexed using angler harvest in Escanaba Lake, Wisconsin from 1956- 1999. Following the introduction and establishment of walleye Stizostedion vitreum and northern pike Esox lucius in Escanaba Lake, smallmouth bass Micropterus dolomieu, largemouth bass Micropterus salmoides, pumpkinseed Lepomis gibbosus, bluegill Lepomis macrochirus, black crappie Pomoxis nigromaculatus, and yellow perch Perca flavescens populations declined nearing extirpation during the 1960s. Since 1964, the Escanaba Lake sport fishery has consisted of walleye, northern pike, muskellunge Esox masquinongy, and a recovered yellow perch population. Centrarchid populations are still near extirpation levels and rarely are creeled. Overall, angler harvest shows a bifurcated relation with effort that correspond to four chronological time periods suggesting different ecological and sociological processes affected annual catch rates throughout the history of the fishery. There were significant relations between harvest and effort for many species and all were linear, suggesting that harvest had not attained an asymptote (i.e., harvest was still increasing with increasing effort with no evidence of density-dependence). When anglers identified targeted species ( directed effort), directed effort predicted harvest better than total annual effort for all species except muskellunge. Overall, sport angler harvest was significantly related to species abundance for yellow perch, bluegill, black crappie, walleye, northern pike, and muskellunge from 1956-1999. During the modem day fishery from 1964-1999, walleye, yellow perch, and northern pike harvest was a significant predictor of abundance. This study shows that effort and harvest are significantly related and that harvest can be used to index abundance of fish in Escanaba Lake, which holds promise for other similar lakes.