Movement, resource use, and life history strategies of Black Bay Walley (Sander vitreus)

Abstract

Resource distribution across the landscape can drive movement strategy selection, from sedentary to highly mobile individuals. When paired with other forms of analysis, movement ecology can provide insight into the resource use, habitat selection, and life history strategies of fish. Acoustic telemetry has greatly improved our understanding of fish movement in the Laurentian Great Lakes, and Walleye (Sander vitreus), as a fish of great economic and social importance, have been intensively studied. While the degree of migration through the Great Lakes has been assessed, there remains a knowledge gap surrounding within-population variation in this movement. Black Bay once supported the largest commercial fishery for Walleye on Lake Superior, until its collapse in the late 1960s, and the recovery of this population has become a management priority on the lake. Management decisions have however, lacked precise information on the spatial extent, resource use, and life history of Black Bay Walleye. My thesis makes use of a two year acoustic telemetry study to assess Walleye movement within Black Bay and into the main body of Lake Superior. This was done with the goal of identifying Walleye movement patterns, and the influence of thermal-optical habitat and forage availability on these movement patterns. Black Bay Walleye have distinct migratory and resident groups, where migrators leave Black Bay during part of the year, and residents remain within Black Bay all year. Using a traditional Von-Bertalanffy model to describe growth, I found that migratory Walleye achieved a greater asymptotic length than residents, but that the curvature of these growth patterns did not differ between groups. Thermal-optical habitat conditions outside of Black Bay influence occupancy of this region by migrants, but occupancy of the north end of Black Bay is not limited by available thermal-optical habitat. Migratory and resident Walleye from Black Bay did not differ in prey use (assessed using stable isotopes), and forage availability did not differ between regions within and outside of Black Bay. Historical differences in coregonid abundance between Black Bay and the region outside of the bay may, however, have led to the disparity in movement strategies still observed today.