As summer heats up and fishing season reaches a full swing, some anglers might be wondering just how the Minnesota Department of Natural Resources (DNR) is managing area lakes.
Marc Bacigalupi was at the June Chautauqua in Crosslake June 12 to tell the tale of fisheries management, specifically on the Whitefish Chain.
Bacigalupi, the DNR area supervisor of the Brainerd fisheries office, explained that his office is in charge of Crow Wing and southern Cass counties, comprising 400 bodies of water, including 100 that are managed.
Bacigalupi said the office uses science-based management for its fisheries. The backbone of the practice is fish surveys.
“If we don’t know what the current state of the water body is,” he said, “It’s pretty hard to develop a plan.”
The DNR’s management program begins with the egg take, just upstream of where the Pine River enters Upper Whitefish Lake. It’s a long-running practice, dating back to 1922.
They gather 750 quarts of eggs from the females, which they fertilize with the males. Because each quart has around 125,000 eggs, the total collected ranges around 87 million eggs. Getting a 67 percent success rate, the DNR hatches around 58 million eggs at their hatchery in Brainerd.
To meet their quotas, the DNR handles 2,500 walleye a year at egg take. The eggs are then hatched and released into area lakes. The Whitefish Chain always gets extra eggs because that’s where they were collected from.
In the early 2000s, Bacigalupi said, the DNR began tagging walleye at the egg take site. The walleye are tagged with colored plastic that’s inserted into the underside of the fish’s jaws.
The practice has since stopped, but the tagged walleye were found throughout the Whitefish Chain, Bacigalupi said. This indicates that walleye don’t have site fidelity—they don’t always return to the same place.
In addition to stocking lakes with freshly-hatched walleye fry (babies), the DNR also raises fingerlings. The eggs are distributed over many natural ponds in the spring so that the “eggs are spread around literally into many baskets,” he said, adding, “The name of the game is lots of ponds.” In the fall the six-inch walleye are netted, numbers are recorded, they’re loaded onto a truck and released through a four-inch hose into area lakes. Bacigalupi said the success in the ponds is “hit or miss. They either do really well or it’s a complete failure.”
The walleye fingerlings are stocked in the Whitefish Chain on even-numbered years.
Fish population surveys are conducted every five years, he said. Most recently the surveys were conducted in 2005 and 2011. Fish are caught with gillnets and trap nets, and the DNR records the species present, the abundance of that species, size distribution, age and growth.
Age is determined by observing fish scales under a microscope. The scales have rings, which show years in a similar fashion as tree trunks. Bacigalupi said growth rates are a function of water quality, length of the growing season, food availability and competition.
When netting the fish, Bacigalupi said, the DNR also measures the catch per unit effort, catch per net and catch per hour.
Another measurement of the fish population is the annual electrofishing that’s done on the Whitefish Chain. Bacigalupi said that every year in the fall the DNR electrofishes the same places and records information about what’s caught. The electric current stuns the fish temporarily.
When electrofishing, the DNR records the young-of-year fish—those that survived the year from when they were released in the spring. They’re measured, recorded, and scale samples are collected.
“It gives us information on that year’s class of walleye,” Bacigalupi said. The data is then compared to other years.
The 2011 survey showed that compared to the statewide average for lakes of a similar type as Whitefish (like Gull or Pelican), the population was fairly low.
Walleye are stable, Bacigalupi said, but not at a high abundance level. Perch are down, which are an important food source for walleye and northern. Their catch per effort rate went from 27 in the ‘90s to only one in 2011.
Answering perhaps the most sought-after question among anglers, Bacigalupi said the estimated walleye population in the chain is 21,000. That means there’s one walleye that’s more than 16 inches long for every 1.5 acres. Bacigalupi said walleye fishing was reportedly good in 2012.