Increasing demand brings DNR action
The state has imposed a new set of fishing limits on walleyes, the marquee game fish in Storm Lake, in an attempt to increase the number of big fish developing in the lake.
Starting this winter on Storm Lake, all walleyes between 17 and 22 inches in length must be immediately released. The daily bag limit will remain at three walleyes per day, and only one walleye over 22 inches can be harvested.
Over time, experts predict that the walleye broodstock in Storm Lake will grow by over 25 percent under the new regulations.
Walleyes draw many anglers to Storm Lake, and are one of the most popular targets in the Iowa Great Lakes. Each year 30%-50% of anglers specifically fish for walleyes even though walleyes usually constitute less than 1% of the total harvest of fish caught on the area lakes.
Besides being important walleye fisheries, these lakes are the main source of broodstock walleye for the Spirit Lake Hatchery.
Due to increasing demands for more walleye, the production of the hatchery was expanded by 50% in 1978 to a capacity of 840 quarts of eggs. This translates to a production of over 80 million walleye every year. Fish are stocked all over Iowa.
"It is absolutely critical we maintain adequate numbers of large walleyes in these lakes to meet both the demands of the angler and the production demands of the Spirit Lake Hatchery," said Lanny Miller, fisheries biology expert for the Department of Natural Resources.
Walleye populations tend to be cyclic, with large year-classes of fish every 3-5 years, followed by weak year-classes. "We have observed these cycles for over a hundred years in our lakes, and we have concluded that these cycles will always be with us," Miller said.
Walleyes are extremely cannibalistic, and readily eat smaller walleyes. When a large year-class of walleyes develops, these fish cannibalize heavily on smaller walleyes for a few years, effectively suppressing the development of a new strong year class. As this year class matures and grows larger, they switch to bigger forage allowing for increased survival of the stocked walleyes again.
These cycles in walleye abundance are a challenge for fisheries managers. Anglers tend to be satisfied when walleye populations are high, and disappointed during slumps.
"When walleye abundance is high we can literally fill the hatchery in a few nights of netting. However, during years of low abundance it may take many weeks of intense netting to catch enough walleyes. Since 1987, additional walleye eggs were obtained from Clear and Storm Lakes to offset any shortages. The challenge for fisheries managers is how to increase the numbers of large walleyes in our lakes dominated by these cycles?" Miller said
On Storm Lake, the Iowa Great Lakes and Clear Lake restrictions on walleye fishing were first added in 1987. In 1991, a 15-inch minimum length limit was imposed on Storm Lake. The daily bag limit was reduced from 5 to 3 fish per day, and the possession limit was reduced from 10 to 6 fish. Only one walleye could be greater than 20 inches in length could be kept at the lakes, except in Storm Lake where only one walleye could be over 22 inches in length.
"The goals of these regulations were to increase yield, spread out the harvest to more anglers, increase catch rates, decrease harvest of small fish, decrease mortality of sub-legal walleye, and, ultimately, increase the number of large, especially broodstock, walleye in these lakes, " Miller said.
Anglers cooperated, but the rules but did not adequately increase the numbers of broodstock walleyes in the lakes, Miller said.
So, beginning in January 2007, a protected slot limit of 17-22 inches will be in effect on Storm and the Iowa Great Lakes. A protected slot limit means that all walleyes between 17 and 22 inches in length must be immediately released. The daily bag limit will remain at three walleyes per day, and only one walleye over 22 inches may be harvested.
It is a big change, Miller notes. In the past anglers were required to release all small walleyes (under the length limits) and were allowed to harvest larger walleyes. Now anglers will be encouraged to harvest smaller walleyes (under 17 inches) and must release most larger walleyes (with the exception of one large walleye over 22 inches).
"This type of regulation has worked in other systems and we are confident that we should see positive results in these lakes. In fact, we predict the numbers of broodstock walleye will increase about 20% in Spirit Lake... and increase nearly 27% in Storm Lake," Miller said.