Muskellunge Spatial Ecology in the St. Louis River Estuary and Southwestern Lake Superior

Abstract

The St. Louis River estuary is a designated area of concern by the U.S. Environmental Protection Agency due to severe environmental degradation. The spatial ecology of Muskellunge Esox masquinongy, an indicator species, is uncertain within the estuary and the large, connected water body, Lake Superior. We collected genetic samples and used passive acoustic telemetry to track 60 adult Muskellunge in the St. Louis River estuary and southwestern Lake Superior for 15 months. Genetic analysis revealed that the river is utilized by two genetic strains-Wisconsin (WI) and Minnesota (MN)-and their hybrids. These genetic strains were previously stocked to restore a nearly extirpated population. Muskellunge tended to move upstream in the spring, downstream and into Lake Superior throughout summer, and to the middle river during fall and winter. Males and females spent significantly more time in the upper and lower portions of the river, respectively. Movements were influenced by strain in that hybrids and the WI strain spent more time in the upper and middle river, and the MN strain spent more time in Lake Superior. A random forest model indicated that Lake Superior use was related to strain (the MN strain made up 80% of individuals using Lake Superior) but not sex or body length, highlighting the importance of understanding strain behavior when stocking different strains. Future research should include investigating Muskellunge habitat use (before, during, and after restoration), tracking juvenile Muskellunge, and connecting telemetry data with mark-recapture and stable isotope data. Our results provide new insight into Muskellunge spatial ecology and genetics that can inform management and restoration efforts within and beyond the Great Lakes.

The Movement Ecology of Freshwater Fishes in an Urbanizing River System

“…Overall, these seasonal trends align with other seasonal movements of muskellunge reported in the literature, where high levels of activity and movement are observed in the fall and spring seasons compared to the summer (Gillis et al, 2010;Pankhurst et al, 2016;Schaeffer et al, 2020). Summer movements were the most restricted for muskellunge in this system and most resident to the middle section of the river once again, although further upstream than fish normally occupied in the fall, spring, and winter.…”

“…My research contributes to expanding our collective knowledge of the movement ecology of fishes in urban systems. I demonstrated that muskellunge seasonal movement patterns in relatively small and narrow urban waterbodies are similar to the movements of muskellunge in larger, lake or river systems (Dombeck 1979;Diana et al, 2015;Schaeffer et al, 2020;Hessenauer et al, 2021). My research also focused on under-studied, smaller-bodied freshwater fishes that are ecologically important but often receive relatively little conservation attention (Olden et al, 2007;Saddlier et al, 2013).…”

“…More mobile muskellunge have also been observed in the St. Louis River Estuary, USA where 16 individuals spent time in six different river segments and only five individuals stayed resident to two segments (Schaeffer et al, 2020). These are both larger systems than the Jock River, and more area/space for movement likely influences muskellunge mobility.…”

An Interdisciplinary Approach to Evaluating Native and Invasive Fish Connectivity and Spatial Ecology in Canada’s Historic Rideau Canal Waterway

“…However, most of our tagged muskellunge moved to a different river segment once connectivity was restored in April (see section "Reach connectivity"), so it is unlikely muskellunge remain in a single region all year. This is consistent with Pankhurst et al (2016) who found that most of their tagged muskellunge (a study also conducted in the Rideau Canal) increased activity levels in spring and Schaeffer et al (2020) documented muskellunge exhibiting seasonal shifts in spatial use. We did not conduct surveys to evaluate persistent (winter) vegetation or woody debris, though these structures may have been present…”

“…Most muskellunge that displayed increased activity were close to (within 100 mm) or longer than 700 mm, which in Ontario is generally considered size-at-first maturity (Casselman 2007). Larger spring movements by muskellunge, presumably driven by spawning temperatures, have indeed been documented in the Rideau River (e.g., Pankhurst et al 2016) and in other North American systems (e.g., Schaeffer et al 2020;Weber and Weber 2021).…”