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Stocking walleye and other species is tedious but rewarding

Minnesota Department of Natural Resources large lake specialist Doug Schultz, at right, gently "strips" a female walleye at a walleye trap near Woman Lake. The eggs are mixed with milt, carefully stirred with a feather and eventually brought to a hatchery, where their hatch rate is much greater compared to the natural world. (Jason Durham / For the Enterprise)

The 2009 Minnesota Fishing Opener has finally arrived amidst a buzz of activity; anglers purchasing a new fishing license, bait shops scurrying to count worms and leeches to fill their coolers and gas stations overflowing with vehicles and trailers as people get ready to embark on their opening weekend exploits.

The Minnesota Department of Natural Resources has also been busy preparing for opener, but their strategies start months -even years - ahead of time.

One of its major contributions to the fishing success of others is stocking. That process begins with DNR staff and volunteers "stripping" walleye in the spring: taking the natural eggs and milt from walleye on certain bodies of water and hatching them in captivity.

To gather the precious walleye eggs, a group of nets and docks are erected in a lake tributary and left to gather fish overnight. The next day, the gathered fish are separated by gender. DNR staffers take one fish at a time, first a female, then a male and gently "milk" the reproductive elements into a plastic dish. That dish is passed on to another person who adds a watery solution of bentonite clay to prevent the eggs from sticking together. Then the eggs, milt and bentonite are gently stirred together using a goose feather. Once the eggs have been carefully rinsed, they go into a large cooler and begin their journey to the fish hatchery.

According to Park Rapids Area Fisheries Supervisor Doug Kingsley, prime natural spawning habitat for walleye is clean gravel or rubble that is windswept or has current (for mixing the eggs and milt). Throughout the state, natural reproduction and survival numbers for walleye are low on certain bodies of water due to a lack of prime spawning habitat. "Walleye will also deposit eggs on poorer quality substrates", adds Kingsley. "On good habitat, up to 25 percent of eggs might hatch. On poorer habitat, less than 1 percent may hatch." In a hatchery, 60 percent of the eggs typically hatch.

"The best reason for hatching eggs in captivity and stocking is in situations that have good conditions for a walleye population: suitable habitat, temperatures, water quality and forage, but lack good spawning habitat. In other words, spawning habitat is the limiting factor for a good walleye population," says Kingsley. "In those conditions we can stock walleye either as fry or fingerlings, get over the spawning habitat hurdle, and produce a good walleye population. Unfortunately, people often want walleye in lakes that have other limiting factors, like poor habitat, high water temperatures, poor water quality or limited forage. In those situations survival will be much poorer. We may get a few fish surviving, but they may have poor growth or conditions or not reach suitable sizes. Or, it may even have negative effects on fish that are better suited to those conditions."

Though survival rates vary, one of Kingsley's sources says that in the natural environment, on average, 1 fry in 1,000 (0.1 percent) might survive to fingerling size. About 5-10 percent of fingerlings survive to catchable size, but that number varies in different types of waters.