Millions of walleye fry (babies) tasted freedom for the first time last week as they were released into area lakes after spending the beginning of their lives at the Minnesota Department of Natural Resources (DNR) hatchery in Brainerd.
On Friday, May 31, 1.53 million walleye fry were released into the Whitefish Chain, adding to the 4 million that had already been stocked in the chain. The May 31 fry went to Cross and Rush lakes, but other areas of the chain were also stocked, with a total of 15 million fry stocked in the chain.
The DNR also stocked millions of fry into other area lakes, including Horseshoe, Upper Hay, Edward, North Long and Pelican.
The fry, which are about the size of mosquitoes when they’re released, are only days old when they enter the lake. Fisheries specialist Carl Mills explained that the fish have to be released within a few days of hatching because they need to feed.
When they’re still in their eggs, the walleye feed on a yolk sack, Mills said, but when they fully leave the egg, they must eat soon, or the fry could start eating one another.
The eggs were collected and fertilized on the Pine River a little ways upstream of Upper Whitefish Lake in mid-May. From fertilization to hatch is about three weeks, Mills said. This year the walleye spawn and hatch were late due to the late spring.
DNR fisheries specialist David Lockwood said that normally walleye are released before fishing opener, but this year the fisheries crew released the last of the walleye fry Friday, May 31.
The eggs are collected and fertilized at the Pine River egg take site every spring, then brought to the hatchery where they’re placed in large jars with circulating water. The system allows hatched fry to swim up and out of the jars (the eggs sit on the bottom) and then the water current moves them through a series of troughs and into a holding tank.
This year the hatchery had a hatch rate of 83.5 percent, the highest Mills has seen. The average hatch rate percent is in the mid-60s, he said.
Mills said the entire hatchery system is automated, with an alarm system set to call him should there be a problem. He said that by controlling the temperature, he can control the hatch rate. The walleye are more likely to hatch at warmer temperatures.
Mills uses a formula: Each day the water temperature is measured. They keep track of the number of degrees the water is above 32 every day, adding that amount together day after day. When that number gets to around 350, that’s when the hatching gets going.
Mills and the hatchery team do their best to match the water temperature in the hatchery to the water temperature in the lakes for a better survival rate. Mills said that around the time of release, Gull Lake was around 52 degrees, while Mille Lacs was at 49 degrees.
When the fry are ready to head out to the lakes, they’re measured by weight and transferred into containers for travel. Each bucket generally gets 100,000 walleye fry, which weighs .86 pounds. Oxygen is added to the containers for the ride to the lake.
The walleye are then released in the center of the lake. Mills said that releasing the fry in the middle of the lake gives them a better shot at survival because there are fewer minnows and other fish to eat them.
Only 1-2 percent of the fry make it to a catchable size, at 13 or 14 inches, Mills said. That means that if 5 million are stocked in a lake, 100,000 will become catchable adults.
The DNR will also stock fingerling walleye, but the process is more expensive than raising and releasing fry.
Mills said that when the DNR raises fingerling walleye, they use natural ponds. Fry are released into the ponds in the spring, and then fingerlings are netted and released into designated lakes in the fall.
Why does the DNR go to such lengths to stock lakes with walleye?
“Because Minnesotans love walleye,” Lockwood said.
Lockwood said that the process also gets a higher hatch rate than in nature, because it prevents against things like floods, which would wash away the eggs, water temps that are too hot or too cold and predators.
“You remove a lot of variables in the hatchery,” Lockwood said.
Mills said he has hatchery records that date back around 100 years. Many lakes are stocked, including some that would not otherwise be walleye lakes. The Whitefish Chain gets stocked with extra fry because the eggs are taken from that area.