Two decades of genetic consistency in a reproductive population in the face of exploitation: patterns of adult and larval walleye (Sander vitreus) from Lake Erie’s Maumee River

Abstract

Analyses of genetic variability and allelic composition in a species exhibiting reproductive fidelity to natal sites may provide important ecological indication of temporal population dynamics, facilitating understanding responses to past disturbances and future climate change. The walleye is an ecologically and economically valuable species, whose largest fishery centers in Lake Erie of the Laurentian Great Lakes; it exhibits reproductive site fidelity, despite otherwise wide-ranging dispersal. We tested whether genetic composition and diversity have remained temporally stable in Lake Erie’s Maumee River, which is the largest and most highly fished spawning run. This population has experienced over a century of exploitation, habitat alterations, and pollution, which may have affected genetic structure and might influence future sustainability. Fourteen nuclear DNA microsatellite loci were analyzed from 744 spawning run walleye to test genetic patterns across: (1) years (N = 12, spanning 1995–2013), (2) birth year cohorts, (3) the sexes, (4) those reproducing earlier (ages 2–6) versus later (7 or older) in life, and (5) the adults versus larvae. Results indicated stability in genetic diversity levels (mean H O = 0.76 ± 0.03) and allelic composition across years (F ST = 0.000–0.006, NS), cohorts (F ST = 0.000–0.013, NS), sexes (F ST = 0.000, NS), earlier versus later reproduction (F ST = 0.000, NS), and between the larvae and adults (F ST = 0.000–0.004, NS). Number of breeders and effective population size were substantial and consistent. This reproductive population thus has maintained genetic stability and high diversity, despite intensive anthropogenic pressures.