Behaviors that affect the distribution of fish within aquatic systems are important considerations in the design of sampling programs. Although movements consistent with reproductive homing have been documented for muskellunge Esox masquinongy in relatively large, complex systems, quantitative data describing their distribution at the restricted spatial scale relevant to small lake fisheries are lacking. We sampled muskellunge by means of fyke netting over 2 years in each of four Wisconsin lakes with surface areas between 110 and 588 ha. Individual capture locations were recorded. Each muskellunge sampled during the first year was injected with a passive integrated transponder to allow identification of the individuals recaptured during the second year. The number of recaptures with functional transponders during the second year ranged from 15 to 43 per lake. Capture site fidelity, defined as the percentage of recaptured fish being found in the same spawning area in two consecutive years, varied from 55% to 93%. The results are relevant to population estimation and broodstock collection for artificial propagation. Population estimates need to include all spawning habitats because marked and unmarked fish are not well mixed throughout the lake during the spawning season. Because repeated netting effort at the same locations among years is likely to resample individuals used for broodstock collection, netting effort should be dispersed among spawning sites.
Egg distribution and spawning habitat of northern pike and muskellunge in a St. Lawrence River marsh
Coexistence of northern pike Esox lucius and muskellunge Esox masquinongy in the Niagara and St. Lawrence rivers has been hypothesized to depend on segregation during spawning. However, large overlap in the use of spawning areas by these two species occurs in the Thousand Islands section of the upper St. Lawrence River. In this study, egg collections in Point Marguerite Marsh in the upper river revealed a partial temporal and spatial overlap in egg deposition by northern pike and muskellunge. Northern pike began spawning earlier but overlapped with muskellunge spawning for 2 weeks, May 13–27. Northern pike eggs were collected over a larger area than muskellunge eggs and at all locations where muskellunge eggs were collected. Both species deposited eggs over three dominant genera of vegetation: pondweeds Potamogeton, duckweeds Lemna, and stonewort Chara. Northern pike spawned over a wider range of water depths (0.5–2.6 m) than muskellunge (0.8–1.5 m) and selected habitats with denser, taller vegetative cover. The temporal and spatial overlap of northern pike and muskellunge egg deposition suggests that mechanisms other than spawning segregation permit these two species to coexist in the St. Lawrence River.
Potential effects of spawning habitat changes on the segregation of northern pike and muskellunge in the Upper St. Lawrence River
Changes in spawning habitat of northern pike (Esox lucius) may affect their segregation from and coexistence with the closely related muskellunge (E. masquinongy). We estimated the areal coverage of robust and shallow emergent vegetation in three shared-spawning bays in the Upper St. Lawrence River from aerial photographs taken from 1948 to 2003. Robust emergent vegetation (e.g., cattail) increased in coverage by 155–241% while shallow emergents (sedges) decreased by 46–96%. The loss of sedges, an important northern pike-spawning habitat, may facilitate greater spawning overlap in offshore-submersed aquatic vegetation within bay habitats used by muskellunge. Development rates and characteristics of northern pike and muskellunge eggs and larvae were compared to better understand the implications of greater spawning overlap. Northern pike eggs developed faster than muskellunge eggs at temperatures of 4.7–19°C, and adhesive eggs and the presence of adhesive papillae were present in both species. Equations were used to predict degree-day requirements for hatching and swim-up in three habitats (shallow emergents, bay, and offshore shoal) along a temperature gradient. Northern pike required more estimated degree days to reach hatching in bay and offshore shoal habitat relative to shallow emergent habitat due to cooler temperatures. Significant spawning overlap is known to occur within bay habitats, but poor success of northern pike in deep bay habitats and overall reductions in abundance are hypothesized to currently buffer muskellunge from potential negative interactions between these species.
Development of a multi scale wetland resilience index from muskellunge nursery habitat in Georgian Bay, Lake Huron
In a 2012 study, no age-0 muskellunge (Esox masquinongy) were found in any of 16 historic nursery sites in coastal marshes of southeastern Georgian Bay (SEGB), and this was attributed to sustained low water levels (1999–2013) that had altered the vegetation structure of nursery habitat. In the same study, age-0 muskellunge were found in 16 coastal marshes surveyed in northern Georgian Bay (NGB), even though these sites had been subjected to the same water-level conditions. We hypothesize that hydrogeomorphic features of NGB sites made them resilient to effects of sustained low lake levels that made the SEGB sites unsuitable for age-0 muskellunge. Compared to their SEGB counterparts, the NGB nursery sites were significantly steeper, deeper, and less sheltered under low water levels. We used these hydrogeomorphic features to develop a multi-scale Resilience Index (RI) for identifying coastal wetlands that are resilient to stable low lake levels. The RI correctly classified the NGB and SEGB nursery sites, with an area-under-the-curve score of 0.973. Coarser-scale variants of the RI provide a regional screening tool in the identification of resilient wetland habitat (e.g. potential muskellunge nursery habitat), and a basin-wide approach to identify vulnerable wetland habitats. This multi-scale index, in conjunction with targeted field surveys, should provide managers a useful tool in the face of uncertain water level forecasts.
Comparative spatial ecology of sympatric adult muskellunge and northern pike during a one year period in an urban reach of the Rideau River, Canada
The reach of the Rideau River that flows through Ottawa, Ontario supports a recreational fishery for northern pike (Esox lucius) and muskellunge (Esox masquinongy). The reach is unique not only because such a vibrant esocid-based recreational fishery exists in an urban center, but that these two species co-occur. Typically, when these species occur sympatrically, northern pike tend to exclude muskellunge. To ensure the persistence of these esocid populations and the fisheries they support it is important to identify key spawning, nursery, foraging and over-wintering locations along this reach, and to evaluate the extent to which adults of the two species exhibit spatio-temporal overlap in habitat use. Radio-telemetry was used to track adult northern pike (N = 18; length 510 to 890 mm) and adult muskellunge (N = 15; length 695 to 1200 mm) on 73 occasions over one year, with particular focus on the breeding seasons (early April until the end of May [56 % tracking effort]). For the two esocids, we observed 19–60 % overlap in key aggregation areas during each season and during the spawning period. The minimum activity (average linear river distance travelled between consecutive tracking events) and core range (linear river distance within 95 % C.I. of mean river position) were greatest in the winter and fall for northern pike and in the spring for muskellunge. On average, northern pike were considerably smaller than muskellunge and had lower minimum activities and smaller core ranges, which could be a result of thermal biology, limited suitable habitat, prey availability or predation. Results from this study will inform future management of these unique esocid populations and should be considered before any habitat alterations occurs within or adjacent to the Rideau River.
hirty year update: Changes in biological characteristics of degraded muskellunge nursery habitat in southern Georgian Bay, Lake Huron
Aquatic vegetation is a critical component of nursery habitat for young-of-the-year (YOY) muskellunge. The trophy status of the muskellunge fishery in southeastern Georgian Bay owes its reputation to the widespread distribution of aquatic vegetation in coastal marshes of this region. Unfortunately, wetland habitat has been in decline because of an unprecedented period of sustained low water levels since 1999. In this study, we strategically resampled 16 historic sites that supported YOY muskellunge in 1981. The sustained low water levels and increased shoreline modifications experienced by southeastern Georgian Bay may have contributed to the current disappearance of YOY muskellunge at those sites. These physical stressors appeared to have altered the habitat structure of the plant community and led to changes in fish communities, making them no longer suitable for YOY muskellunge. The precise mechanisms limiting survival to the YOY stage are unknown because spawning adults have been observed in the area in the spring of 2012 and 2013. These results corroborated previous sampling programs at the historic sites (2004–2005: n = 8 and 2007: n = 16) that employed other fishing gears and protocols as well as a supplemental YOY sampling in 2013 (n = 26 additional sites). If this muskellunge population is to remain self-sustaining, a complementary management strategy specifically developed for Georgian Bay is required. The strategy should identify and ultimately protect suitable muskellunge breeding habitat by accounting for the unique geomorphology, current physical stressors affecting Georgian Bay, and the biological links between suitable spawning and nursery habitats.
A conceptual model of muskellunge spawning habitat
The muskellunge is an economically important and often declining sport fish restricted to eastern and central North America. To assist research and management, especially in the Georgian Bay area, a conceptual model of muskellunge spawning habitat was developed from a meta-analysis of available peer-reviewed and technical literature. The model incorporates three primary variables: water temperature (7.5-15oC), dissolved oxygen (> 5 mg/L) at the sediment-water interface, and adequate separation of individual eggs after deposition. The model also assumes that muskellunge spawning occurs in wetlands because of their known association with aquatic vegetation. Secondary variables influencing primary conditions include (1) depth, current and substrate colour (assumed to have an effect on temperature); (2) current, sediment oxygen demand, sediment compactness and plant density (assumed to have an effect on dissolved oxygen concentrations); and (3) particle size and plant density (assumed to have an effect on egg separation). Field validation of these results will help to clarify the relative importance of each variable, and thus allow for refinement of the model.
Muskellunge egg incubation habitat in the upper Niagara River
Identification, conservation, and restoration of spawning and nursery habitats are essential for conserving the self-sustaining population of muskellunge (Esox masquinongy) in the upper Niagara River. The objectives of this study were to describe muskellunge egg incubation habitat, identify the most important habitat features associated with the presence of eggs, and make comparisons between spawning habitats identified through visual observation of spawning adults and collection of eggs. We conducted surveys for muskellunge eggs at four locations from 2012 through 2014 and used logistic regression to identify habitat features related to the presence or absence of eggs. We used Bayesian information criterion to select the most likely model and area under the receiver operating characteristic curve tests to determine variable importance and evaluate the model. One-hundred-thirty-six viable muskellunge eggs and two yolk-sac larvae were collected from 30 locations. The most likely model contained parameters for the percent rank of algae or aquatic macrophyte cover of the substrate and water depth. The percent rank of algae or aquatic macrophyte cover was the most important predictor of egg occurrence, and the odds of collecting a muskellunge egg increased by 100% for every 10 percentile increase in percent rank of cover. Spawning habitat features identified in this study were similar to those identified through visual observation of spawning adults. Muskellunge egg incubation locations and habitats should be protected from development and alteration to ensure the sustainability of muskellunge in the Niagara River.
Muskellunge (Esox masquinongy) feeding habits and habitat preferences in Lake St. Clair
Muskellunge (Esox masquinongy) are an economically and ecologically important species. Yet, our understanding of their feeding habits and habitat preference is limited and incomplete. This study addressed these shortcomings with muskellunge in Lake St. Clair. Muskellunge were captured by trolling on charter boats and electrofishing. Feeding habits were determined by comparing fish consumed to abundance of fish in the lake. Habitat preference was determined by spatially analyzing collected fish catch-per-unit-effort and lake conditions such as depth and submerged aquatic vegetation coverage. Overall, 167 muskellunge were sampled and 77% of them had empty stomachs. White bass (Morone chrysops) was the most common found prey species in their diet. Moronidae was the family composing the largest portion of their diet. Muskellunge were more abundant in water with greater depth. The entire lake appears to have suitable coverage of submerged aquatic vegetation with an average of 67%. In conclusion, muskellunge consumed small amounts of the main sport fish species in Lake St. Clair and likely have minimal impacts on those populations. The majority of Lake St. Clair has the preferred habitat for muskellunge and is likely to be a contributing factor to their large population.