BOULDER JUNCTION, Wis. -- Researchers are culling through anglers’ fish tales from the past half-century to better understand how fish populations in several northern lakes have changed over time and the effect bag and length limits have had on some of those lakes.
Since 1946, anglers who fish Escanaba, Nebish, Pallette, Spruce and Mystery lakes in Vilas County have been required to report to Department of Natural Resources researchers the number and species of fish they catch, and to allow researchers to weigh and measure those fish and determine the sex of the game fish species. That information has gone into a huge, rare database kept at the Northern Highland Fishery Research Area and used in short-term studies that helped determine bag limits and regulations on certain lakes, and the effectiveness of such rules.
Now, for the first time, researchers are looking at the entire 53-year record to answer questions about how those regulations have affected – or will affect -- the fish community as a whole over time.
"We’ve got this enormous database and there’s never been enough manpower to analyze everything in it, so only select records have been studied as priorities have arisen," says Steve Newman, a fisheries biologist who works at the fishery research area. "Now, looking at ecosystem management is a priority. This database gives us the ability to do that."
Adds Tim Simonson, a warm water lakes and regulation specialist in the DNR fisheries bureau, "This kind of long-term, ecosystem-level data is invaluable to us when it comes to evaluating potential new fishing regulations and for documenting long-term changes in angler behavior and fish populations in Wisconsin lakes."
Researchers’ initial examinations of this full 53-year-record are bearing fruit. They have found that changes in the fish populations due to management decisions have to be seen against a larger picture.
"Fish populations change a lot on their own – they’re dynamic," Newman says. "You really can’t document changes unless you’re doing it long term. For example, if you set a length or bag limit for walleye on a lake, an increase in the number of walleye present two years later might have nothing to do with the limit, and everything to do with natural cycles."
Studies now underway using the database include one intended to help researchers learn how intensive harvest of walleye affects the fishery in a lake, and the interaction of walleye with other species, Newman says.
Another study explores changes in community dynamics on 293-acre Escanaba Lake, where smallmouth and largemouth bass, bluegill and black crappie have all but vanished from the lake. "We’ve lost a high quality panfish fishery, and we don’t fully understand why that population went," Newman says. "We need to study the population dynamics to ensure good management on an ecosystem level."
The database provides fertile ground for such ecosystem studies. For one thing, it truly reflects what all anglers are catching on the lakes, not just what a sample of anglers recall catching. "Here we’re actually asking every angler to report the catch, unlike typical creel surveys that extrapolate from a sampling of anglers,’’ Newman says.
For another thing, the database spans 53 years, providing a rare and invaluable record of changes over time as well as containing data from a variety of short-term studies. The database, Newman said, reflects the foresight that researchers and fisheries managers had over the years in recognizing the benefits of such long-term monitoring, and in advocating to keep the database going over all those years. The database is, in fact, so useful that requests come in often from other states’ fish managers and universities doing research for data to support management decisions.
The database will give researchers the necessary long-term records to factor out the effect natural cycles have on a fish population. That allows researchers to isolate the change in population that is attributable to bag limits and regulations. Such information can ultimately be used to test computer models used to estimate the amount of fish safe to harvest.
FOR MORE INFORMATION—Steve Newman (715) 356-5211