Multi-species interactions with artificial causeways in a fragmented lake

Lake Champlain is fragmented by causeways that restrict fish and boat movement between basins, with only small openings for passage. We evaluated potential limitations on cross-basin fish movement using acoustic telemetry data from lake sturgeon Acipenser fulvescens, lake trout Salvelinus namaycush, and walleye Sander vitreus. Crossing frequency at five causeways was determined seasonally and repeated passage across years was investigated for individual fish. All species were observed in each basin where receivers were present and crossed most or all five causeways; however, no juvenile lake sturgeon were observed crossing causeways. Individuals with greater latitudinal range tended to cross more frequently, with most crossings occurring at two causeways between the Main Lake and smaller basins. Total crossing frequency was similar among species, but seasonal variation reflected species-specific differences in spawning seasons and temperature preferences. Few fish crossed causeways overall, but those that did often repeated crossing in subsequent years. Thus, causeways may limit fish movement between basins to few individuals, but those fish make repeated crossings across years, indicating interindividual diversity in movement and exploration behaviors.