Muskellunge Spawning Habitat and Reproductive Success

Abstract

Reproduction of muskellunge Esox masquinongy has failed in many waters that formerly supported self‐sustaining populations. Laboratory experiments were conducted to isolate causes of such failures. Differential mortality occurred among lots of muskellunge eggs incubated in jars of unaceated lake water over substrates of sand, gravel, silt, aquatic macrophytes, wood, tree leaves, polyethylene screen, and bare glass. High and rapid early mortality (days 1–2), attributable to low dissolved oxygen (DO) concentrations (0–0.1 mg/liter), occurred among eggs incubated on leaves and macrophytes. After day 3, Saprolegnia sp. fungus was implicated in high egg mortalities in jars with inorganic substrates and moderate DO concentrations (3.8–4.1 mg/liter). Lowest mortality rates occurred on organic substrates (silt and wood) amidst intermediate DO concentrations (0.4–1.7 mg/liter) and limited fungal infestation. Among eight midwestern lakes and reservoirs, measured DO at the substrate‐water interface in four of them was high (means, 6.0–8.4 mg/liter) and showed little microstratification; these lakes contain self‐sustaining muskellunge populations. The other four lakes showed extreme DO microstratification and virtual anoxia (means, 0.4–2.4 mg/liter) at the substrate‐water interface; muskellunge populations in these lakes are supported almost wholly by stocking. Suitable spawning substrates in these lakes are aerated by annual reservoir drawdown, have inherently low biological oxygen demand, or support dense beds of stonewort Chara sp. Reproductive failure is associated with spawning areas having deep accumulations of organic matter and dense macrophyte growth. Improvements of spawning habitat to prevent or alleviate hypoxia are among the options available to manage this species.

Spatial ecology of adult muskellunge (Esox masquinongy) in the urban Ottawa reach of the historic Rideau Canal, Canada

“…Muskellunge may benefit from decreased water levels over winter, as previous studies have suggested that self-sustaining muskellunge populations and high-hatching success are related to winter drawdown (Dombeck et al 1984;Zorn et al 1998). The drawdown period is believed to result in substrate aeration and organic material desiccation, forming a firmer substrate that may improve muskellunge spawning habitat (Dombeck 1986).…”

Development, implementation, and evaluation of an international muskellunge management strategy for the upper St Lawrence River

“…Natural viability rates could serve as an indicator of spawning habitat quality in terms of environmental conditions such as water temperature and dissolved oxygen concentrations. Dombeck (1984) and Zorn et al (1998) demonstrated how low dissolved-oxygen levels at the spawning substrate-water interface could cause widespread egg losses. Natural coastal wetland processes and biochemical pathways affecting DO microstratification, and the effects of localized eutrophication and flow interruption, are a potential major detriment to muskellunge habitat quality.…”

Expulsion of miniature radio transmitters along with eggs of muskellunge and northern pike––a new method for locating critical spawning habitat

“…Offshore spawning in Lake St. Clair and Leech Lake was different than the shoreline spawning commonly described by Crossman (1990) and others. Dombeck et al (1984) found muskellunge spawning areas in seven Wisconsin and Michigan lakes that were located in shallows near shore (mean depth of the spawning sites was 74 cm). Zorn et al (1998) described muskellunge spawning habitat in four Wisconsin lakes as occurring in shallow ( < 1 m) bays over mucky bottoms covered with dead vegetation.…”

“…Populations of muskellunge Esox masquinongy and northern pike Esox lucius are sensitive to shoreline and related land development that removes vegetation, reduces water quality, and adds biological oxygen demand to sediments (Brynildson 1958;Dombeck et al 1984). Eutrophication affects muskellunge eggs and larvae that are intolerant of low dissolved oxygen concentrations in a microzone along the bottom where they are dispersed (Dombeck et al 1984).…”