Seasonal space use and spatial overlap of lake sturgeon populations inhabiting Lake St. Clair

Abstract

Multi-jurisdictional management of adult lake sturgeon ( Acipenser fulvescens ) requires characterizing seasonal dynamics of their spatial distributions. Despite decades of research into lake sturgeon movement ecology, system-wide spatiotemporal behavior remains poorly understood in large lakes, particularly those with metapopulations differentiated by spawning river or migratory phenotypes. This study described seasonal space use of lake sturgeon populations in Lake St. Clair, a large, shallow lake divided by the international border between the State of Michigan and Province of Ontario. Our objectives were to characterize spatial behavior of adult lake sturgeon by: 1) assessing U.S. and Canadian residency patterns and cross-boundary movements with relevance for interjurisdictional management; 2) identifying seasonally important habitats where sturgeon regularly congregate; and 3) comparing seasonal spatial distributions and behavioral metrics among spawning populations and migratory phenotypes. A large sample of acoustic-tagged adult lake sturgeon of known spawning river and migratory phenotype were detected with a high-density (∼5 km spacing), lake-wide receiver grid. Home ranges estimated via Brownian Bridge movement models indicated near lake-wide use and seasonal variation in areas occupied, total area used, and residency within and across jurisdictional boundaries. Lake sturgeon seasonally congregated in several distinct areas but were not completely segregated by spawning populations or migratory phenotypes. Instead, space use by the two spawning populations followed a seasonally dependent, north-south gradient associated with the location of spawning inlet and outlet rivers. These results suggest that managers consider internationally coordinated approaches, especially for population assessment, that account for seasonal habitat shifts and cross-population and phenotypic mixing.