Somethin' fishy goin' on
It's springtime in Minnesota. Robins return, once dead grass and flowers start to grow again and gamefish start to make their runs upstream to spawn. That's when the Fisheries crew at the Minnesota Department of Natural Resources (DNR) Lake Sallie Hatchery get busy collecting walleye eggs.
According to Fisheries manager Jim Wolters, his crew will collect about 310 quarts of walleye eggs in about a two-week period, which started April 5.
"That takes care of our quota for our lake stocking and our walleye rearing ponds, too," he said.
The operation is fairly simple. The walleyes -- in this case, the Red River strain of fish -- like to make an upstream movement to spawn in the spring. Wolter said they use that instinctive movement in the fish to capture and collect some of the eggs.
The hatchery workers set up a netting system at Dunton Locks on the Pelican River between Muskrat Lake and Lake Sallie.
"Any fish -- walleyes, pike, whatever -- that are trying to get upstream during the evening hours will get caught in the trap," Wolter said.
The nets are set in the late afternoon and collection is in the morning. During the day, the nets are removed and the fish are left to run free, although the fish mostly make their runs at night, Wolter said.
In the morning, a crew of six to eight fisheries workers sort and separate the fish, removing any non-walleyes. Ripe females are separated from "green" females, those not ready to give eggs.
One at a time, eggs from the ripe females are collected or "stripped" in a bowl and the sperm of three to four males are added along with a cup of water, which activates the sperm. The solution is then gently stirred with a feather -- which doesn't damage the eggs -- to insure fertilization.
"We take the eggs that are in the females, but we don't get them all," Wolter said. "So those fish are able to go back out in the lake or continue upstream and spawn."
The fertilization process is done rather quickly, as the eggs are viable for about two minutes and the sperm for only about 30 seconds, Wolter said.
The bowl is then passed to another worker who adds a fine clay solution, which removes a natural sticky coating the eggs have.
"In nature, the eggs will stick to rocks and things like that," Wolter said. "We don't want that in a hatchery setting because we'll get clumping, and then we get fungus and diseases in the hatchery."
That bowl is then passed down the line to have the clay removed in the lake with a fine colander.
The cleaned and fertilized eggs are then collected in a large bin and brought to the hatchery, where they are kept in jars of circulated water for two to three weeks when they hatch and become fry. The 3/8-inch hatched fry swim out of the jar, through troughs and pipes and end up in a tank, where they are kept for several days before being stocked in a lake or rearing pond.
On any given day, about 30 quarts of eggs will be collected, yielding about 120,000 eggs. In one spawning season, about 40 million eggs will be collected and hatched in Detroit Lakes.
The Detroit Lakes and Fergus Falls hatcheries provide walleyes for all of northwestern Minnesota, Wolter said.
"It's fun stuff," he said. "We all enjoy doing this. That's why we're in this field."