Thursday, May 1, 2014

Metro walleye fishery depends on planned stocking

If an angler has caught a walleye in an east metro lake any time over the past couple decades, chances are they can thank Donn Schrader. Around the St. Paul area office of the Minnesota Department of Natural Resources, he’s sometimes referred to as “Papa Walleye.”

While lakes in central and northern Minnesota can rely upon nature to create a healthy walleye fishery, very little natural walleye reproduction occurs in metro lakes. Add in the heavy angling pressure in the metro region, where some 385,000 licensed anglers reside, and it’s clear nature needs a helping hand.

“Without stocking we wouldn’t really have a walleye fishery in the metro region, other than in our rivers,” said Dave McCormack, central region assistant fisheries manager. “If you catch a walleye in an east metro lake, it’s probably a fish that came through this facility.”

Each spring, Schrader – who has worked at the hatchery since 1987 – receives around 30 million fertilized walleye eggs that have been taken by DNR crews from one of several locations in the northern part of the state. The eggs arrive in large heavy-duty plastic bags filled with water. As hatchery manager, it’s his job to make sure that as many of the eggs as possible turn into baby walleyes. On average, about three out of four eggs hatch after three weeks, with water temperatures kept at 50 degrees. The dark little squigglers, known as fry, are then transferred into large water jugs and sent out into the world.

Roughly 30 to 40 percent of the fry are put into any of about 20 rearing ponds, which are small basins without other fish. There, they’ll grow to fingerling size by fall, when DNR fisheries crews return to net them and stock them in larger, fishable lakes. Each year, east metro lakes are stocked with about 8,000 pounds of walleye fingerlings. Between 15,000 and 18,000 pounds of fingerlings are added to lakes across the entire seven-county metro region. The other 60 to 70 percent of the fry go directly into the region’s lakes where, if they’re not eaten by bigger fish or die otherwise, they’ll grow to catchable size in about three years.

Whether a particular basin receives fry or fingerlings, how often and how many, are decisions all based on a lake’s management plan, which takes into consideration the types of other fish present, its size and depth, type of lake bottom, water quality, data from fish surveys, and past experience. Stocking fry is less costly, and it can produce good results, especially in lakes that have experienced winterkill, as many did this year. But fry are vulnerable to being eaten by other fish, and don’t do well everywhere. Centerville Lake in Anoka County, for instance, has built a respectable walleye fishery with regular stockings of walleye fry. But Forest Lake has done better being stocked with fingerlings every other year. To some extent, it’s a matter of trial and error.

“In some lakes fry do well, and in some lakes fingerlings do well,” said T.J. DeBates, DNR east metro fisheries manager. “All of our stocking efforts are based on management plans. We don’t just stock willy-nilly.”

In addition to walleye, the St. Paul hatchery produces about 300,000 pure strain muskellunge fry and some hybrids. Situated just below the bluffs of Mounds Park, the facility is located on the site of the state’s first fish hatchery, established there in 1878 because local springs provided a ready supply of cold clean water, and the nearby railroad tracks made it easy to ship fish all around the state. The hatchery operations were significantly downsized starting in the 1960s, and now the site and buildings serve as headquarters for the DNR’s central region.

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