Lake Sturgeon (Acipenser fulvescens) is a species of conservation concern throughout North America, and healthy populations are rare. Earlier sampling efforts identified the Goulais Bay population in Lake Superior as a potentially healthy population after three years of sampling. With seven additional years of sampling, we updated the earlier analysis and developed a matrix population model to conduct a pop-ulation viability analysis (PVA). We identified a non-linear relationship between cohort strength and May river discharge rate which was incorporated into the population model to evaluate the influence of future discharge scenarios on population persistence. Population size was estimated, with an open-population mark-recapture model, at approximately 5,200 juvenile Lake Sturgeon. This estimate equates to approx-imately 440 mature females and 625 mature males in the population. A population of this size has a prob-ability of extinction of 4 % and 18 % over 250 and 1000 years under status quo conditions. If the May river discharge were to decrease in the future, which may represent the most likely scenario under future cli-mate conditions, our model predicts an increased risk of population extirpation. This indicates that increased management actions may be required to ensure this population remains resilient. Crown Copyright (c) 2022 Published by Elsevier B.V. on behalf of International Association for Great Lakes Research. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

The River Darter (Percina shumardi) is a native, rarely sampled fish that has been detected in relatively small numbers since the 1930s. It has a wide North American distribution, but little is known about the species biology and distribution across the Canadian portion of its range. We revisited many historic sampling locations and sampled additional areas to (i) confirm and update the distribution of River Darters in Canadian waters; (ii) assess relative abundance; (iii) update life history characteristics; (iv) collect diet information; and (v) identify characteristics of River Darter habitat. Since 1990, a total of 1032 River Darters were recorded from 29 waterbodies across three ecoregions. River Darters were observed in relatively high abundances in both the Saskatchewan-Nelson River and Southern Hudson Bay-James Bay ecoregions. While still extant in the Great Lakes-Upper St. Lawrence ecoregion, River Darters persist at low abundance. Life history analyses indicate similar maximum age (age 4) and growth (10 mm/year) to conspecific populations in the United States, while sex ratios are generally skewed towards female dominance. River Darter populations had high flexibility in habitat use and diet, using a range of flows and depths and a variety of seasonally available prey types.