Comparative ecology of Muskellunge and nearshore fish assemblages in the Great Lakes

Studies comparing muskellunge population genetic structure, young-of-the-year (YOY) feeding ecology, and effects of habitat and non-native fishes on fish assemblages at nearshore sites were conducted to advance conservation of Great Lakes muskellunge. Examination of the genetic structure of muskellunge from 15 areas identified nine distinct populations that should be managed as independent fisheries. In order to protect the existing genetic variation among muskellunge populations, non-native muskellunge should not be stocked into waters containing native populations. Young-of-the-year muskellunge exhibited a specialized feeding strategy, with banded killifish, cyprinids, and darters being their most important prey. The non-native fishes consumed by YOY muskellunge included round goby, alewife, and non-native cyprinids (common carp, goldfish, and their hybrids). Additionally, YOY muskellunge of a given length consumed longer fusiform prey (e.g., native cyprinids) than laterally compressed prey (e.g., centrarchids). Muskellunge nursery sites with flowing water, coarse substrates, complex aquatic vegetation, and little or no macroalgae were dominated by native, small-bodied cyprinids. Conversely, larger-bodied centrarchids and yellow perch dominated at sites that lacked measureable stream flow, contained fine substrates, sparse vegetation, and dense macroalgae. Management practices that promote native aquatic vegetation by reducing silt loads to littoral areas and protect habitat from dredging and shoreline development should enhance populations of small-bodied prey fishes and piscivores. Non-native rudd from the Niagara River were mostly herbivorous, feeding on aquatic macrophytes in summer but supplementing their diet with algae and fish in spring and fall. Rudd were in better condition and grew more rapidly than other studied populations, so increases in abundance and range expansion are possible. Furthermore, rudd reproduction was successful at lotic sites but very poor at sites that lacked stream flow. The paradigm of optimal rudd habitat and water bodies vulnerable to invasion should be expanded to include lotic systems, and research identifying how rudd herbivory affects native aquatic communities is needed. To conserve the evolutionary potential of muskellunge, non-native muskellunge should not be stocked, and spawning and nursery habitats and their associated fish assemblages must be protected from further degradation and biological invasions.;Keywords: Buffalo Harbor, Niagara River, St. Lawrence River, genetic population structure, diet, prey selection, littoral habitat, non-native species, rudd, round goby...