Use of Outlet Barriers to Prevent Fall Emigration of Brook Trout Stocked in Adirondack Lakes

Abstract

Outlet barriers in stocked lakes of the Adirondack Mountains were used to test the hypothesis that preventing fall emigration by adult brook trout Salvelinus fontinalis would increase trap-net and angling catch rates as well as the number of large trophy fish. Outlet barriers were maintained during the fall spawning season for 6 years on one lake and 10 years on another lake. We compared prebarrier and postbarrier trap-net and angler catches (1978–1998) in two blocked and two unblocked lakes. Postbarrier availability of brook trout to anglers and trap nets increased significantly in Rock Lake (blocked) but not in Lower Sylvan Pond (blocked) or the two unblocked lakes. However, highly significant increases in angler catches of trophy fish occurred from both blocked lakes. Variables other than emigration, such as number of fish stocked and angling mortality, influenced our ability to detect significant increases in the availability of age-2 and older brook trout in Lower Sylvan Pond. The outlet barriers elicited a population response by stocked brook trout consistent with the hypothesis that emigration losses of mature adults depleted older-aged fish from unblocked lakes. Outlet barriers are a potential management tool; however, managers must consider their specific management goals and the problems associated with seasonally interrupting migratory corridors.