Estimating the distribution of the imperiled pugnose shiner (Notropis anogenus) in the St. Lawrence River using a habitat model

The pugnose shiner, Notropis anogenus, is a small minnow that occurs in the Great Lakes basin and Upper Mississippi River basin. It was listed as 'Endangered' under the Canadian Species at Risk Act (SARA) and by the State of New York, largely due to its rarity, fragmented distribution, and degraded habitat. Our objective was to use species distribution modeling to better understand the spatial extent of suitable habitat for the pugnose shiner in the upper St. Lawrence River and to guide protection of habitat for this endangered species. We performed our analyses with MaxEnt, a species distribution modeling method based on maximum entropy. The pugnose shiner is associated with shallow areas of lakes or slow-moving rivers with abundant submerged aquatic vegetation. Therefore, we created a model based on depth, water velocity, and aquatic vegetation. For water depth and velocity, we used results of a two-dimensional hydrodynamic model from the Upper St. Lawrence River generated and calibrated by Environment Canada. Aquatic vegetation was estimated from a simple algorithm based on water depth and velocity. To minimize the effect of sampling bias in the analysis (i.e., sampling occurred predominantly in shallow waters), we also used restricted depth ranges in model generation. Our model produced highly significant results when depth was not restricted, and significant results for analyses with restricted depth ranges. Our results suggest an abundance of potentially suitable habitat for the pugnose shiner in the Upper St. Lawrence River, which exceeded the minimum area for viable population estimates for this species.