Collecting Muskie Eggs Helps Mother Nature Along
April 14, 2006
On a pleasant and sunny spring morning on the south shore of Thornapple Lake in Barry County, a small crowd gathers, bringing folding camping chairs and cups of coffee.
Department of Natural Resources Fisheries Division staff and a conservation officer make amiable small talk with the crowd as they wait for the show to begin.
Someone spots a DNR boat heading toward the shore. The show is about to begin.
The show is the annual egg collection for northern muskellunge, or muskies, as they are called. DNR fisheries staff collects the large, solitary fish in special trap nets set out on Thornapple Lake for two weeks every spring. The fish are sorted into enclosure nets close to the shore based on sex and degrees of ripeness - whether or not the fish are ready to spawn. Ripe females are placed in holding tanks of water on shore that have had a small amount of MS222, an anesthetic, added to the water. The MS222 makes the large muskie - the record muskie taken on Thornapple Lake was a 49 pound, 12 ounce monster landed in November of 2002 - easier to handle.
Muskies spawn in the early spring shortly after the ice has melted, but after the spawning of northern pike. Eggs are laid among nearby vegetation, in water only 15 to 20 inches deep and with a temperature of about 55 degrees. However, the northern muskies, which are in several lakes around Michigan, often have difficulty reproducing.
"Natural reproduction of muskies is next to nil in Thornapple Lake," said Matt Hughes, a hatchery biologist from the Wolf Lake State Fish Hatchery in Mattawan, who was milking eggs and sperm from the muskie brought in from the trap nets. Hughes said that though some natural reproduction occurs in other inland waters of the state, the DNR uses muskies from both Thornapple Lake and Lake Hudson, located in Lenawee County, for brood stock to incubate and rear fingerlings at the Wolf Lake hatchery. This year's goal was to collect 850,000 muskie eggs. The average female will produce about 50,000 eggs per quart.
When a ripe female is detected - biologists look for a female with a protruding belly, indicating she is full of eggs - she is carefully milked for her eggs. Biologists then locate a male that is not closely related or who has not been used to mate with the female in the past. The male muskie is milked for drops of sperm that are gently mixed on site with the eggs in small white bowls with a little water. The fertilized eggs are then transferred to special buckets for transport to the hatchery.
The eggs are incubated at the Wolf Lake hatchery and the fish are reared to 10 to 12 inch fingerlings that are then planted by the DNR in lakes around Michigan in the fall. Last year, 36,000 muskies were stocked in Michigan lakes.
Fisheries biologists and technicians check every muskie they capture for recently clipped dorsal fins. Dorsal fins are clipped so biologists can age the fish. Small sections of the muskies' tails are collected too for a genetic sample, so Michigan State University researchers can assist the DNR with a database of all the muskie collected for eggs or sperm. Basically, biologists do not want to mix the eggs and sperm of closely related fish to help ensure genetic diversity of the muskie population, said Dan Anson, DNR Fisheries technician supervisor.
Biologists also use an electronic wand to check the fish for a previously implanted passive integrated transponder (PIT) tag. A PIT tag is a radio frequency microchip about the size of a grain of rice that transmits a unique ID code or number to a special detection wand. Unlike the external, metal tag that biologists sometimes attach to a fish's lower jaw or dorsal fin, a PIT tag will not be noticeable to anglers. A syringe is used to place the PIT tag just under the skin in the head area, if the muskie does not already have one.
The crowd of about 30 local residents marvels at the large muskies that have been trapped and are hauled to the shore by the DNR employees. They ask questions about the fish and the egg take process every step of the way. "It's biology in action," one remarks.
Muskies are a member of the northern pike family, and are known as an extremely efficient "predator machine." It lurks near shore in the shadows of plants or submerged logs, striking swiftly at a prey fish. During the peak summer heat months, the muskies may move into slightly deeper, cooler waters, but will still choose the protection of a drop-off or some underwater obstruction. Larger muskies will attack and consume nearly every living animal, including small rodents, waterfowl and muskrats. They are the second biggest fish in the Great Lakes region, second only to sturgeons.
Muskies are known as tasty game fish, but fierce fighters if hooked by an angler. Sometimes, according to reports, they can take up to an hour to land. Small muskies often are a prey fish for larger fish, like northern pike, sunfish and yellow perch. Adult muskies are most threatened by bears, large birds of prey and people. It is a fish often poached out of season because of its habit of spawning in shallow water.
The muskie season varies across the state. Interested anglers should consult the DNR's 2006-08 Fishing Guide for season information and special regulations. The fishing guide is available at all license dealers or online at www.michigan.gov/dnr under the Fishing section.