Muskellunge
Muskellunge and northern pike are closely related, popular midwestern sport fish that have recently become "reproductively challenged." Historically, muskellunge and northern pike moved to shallow waters during the early spring months to spawn. Males and females would pair up and release millions of eggs that drifted to the bottom where, without parental care, they developed in the substrate (bottom material) and hatched in one to two weeks time.
Unfortunately, this annual right of spring was interrupted by modern-day pollution and development that destroyed many spawning areas. To maintain population levels, fisheries managers have had to raise muskellunge and northern pike in hatcheries and stock them in the wild. However, there is now an interest in turning back the hands of time -- restoring the spawning areas -- and having muskellunge and northern pike successfully reproduce.
Restoration projects have been attempted for both muskellunge and northern pike. These projects have entailed activities such as reclaiming swampy and marshy areas to placing certain substrates in areas where fish are thought to spawn. Unfortunately, restoration efforts have been hit-or-miss propositions; sometimes they've worked, other times they have failed to aid northern pike and muskellunge reproduction.
Muskellunge
Northern Pike
In reviewing past restoration attempts, it was evident that we do not know which substrate (or substrates) is best for muskellunge and northern pike spawning areas. Substrates are important because they establish an environment for fish eggs. Some substrates are known to smother eggs, but others provide support and aeration. Some substrates provide oxygen to the eggs, while others take it away. Some substrates are even thought to give off chemicals that inhibit bacterial and fungal growth, thus providing protection to the developing eggs.
The object of our study was to find the best substrate(s) for northern pike and muskellunge eggs. We tested the survival of muskellunge and northern pike eggs on the following substrates (grouped into four categories):
1. Live submerged plants:
Potamogeton crispus (curly leaf pond weed)
Myriophyllum sp (Mil foil)
Chara sp.
2. Dead plants:
Typha spp. (cattail)
Sedge grass
Dead leaves (oak, maple)
Wood
3. Artificial plastic plants
4. Nonplant substrates:
Clean gravel
Sand
Compacted mud
We constructed this list of substrates from past papers on muskellunge and northern pike breeding biology. Each paper suggested a different substrate or group of substrates as being the best for muskellunge and northern pike spawning areas. The 11 substrates listed above were mentioned most often in the articles we read. (The plastic plants, like you find in pet stores, were not mentioned in the articles, but we thought it was important to include them in the study because restoration project managers might be interested in using them.)
The substrates were placed into 1-gallon glass jars in our laboratory. We had 55, 1-gallon glass jars, which meant there were five jars per substrate, or five repetitions per substrate. The water temperature in the jars was held constant at 13 o C (the spawning temperature for muskellunge and northern pike) and the light was on a 12:12 cycle -- 12 hours of light and 12 hours of darkness.
We obtained two batches of muskellunge eggs and two batches of northern pike eggs. We placed 50 eggs into each jar, and we tested one batch of eggs at a time, alternating between muskellunge eggs and northern pike eggs.
On a daily basis over a two-month period, we tracked the hatching and survival of the muskellunge and northern pike eggs. For muskellunge we found that gravel is the best substrate, while sand, mud, and Myriophyllum are poor. The remaining substrates of Potamogeton, Chara, cattail, dead leaves, wood, artificial plants, and sedge grass were intermediate or "so-so" for muskellunge survival. For northern pike we found Myriophyllum, wood, and mud are poor, whereas the remaining substrates were good to intermediate in quality.
It was interesting to see the different results for muskellunge and northern pike eggs, and we believe they correspond to the differences in breeding biology between the two species. Even though both fish spawn at the same time and in the same general manner, muskellunge prefer to lay their nonadhesive eggs in highly ventilated, well-oxygenated areas of water (i.e., lotic or riverlike environments), whereas northern pike prefer to lay their adhesive eggs in marshy or swampy areas of water (i.e., lentic or lakelike environments). Of all the substrates, gravel best provides the well-oxygenated, clean environment needed for muskellunge eggs. Of the substrates that are good to intermediate for northern pike, most are organic in nature, which matches the swampy environment they desire.
We hope that the information obtained in this study will help fisheries managers as they attempt to turn back the hands of time and successfully restore muskellunge and northern pike spawning areas.
Doug Wojcieszak and Dave H. Wahl, Center for Aquatic Ecology. Vic Santucci, Max McGraw Wildlife Foundation.
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Last Modified 3/19/96