Improving Walleye and Musky Fishing in Iowa Project Update

By Ben Leal

Walleye always seem to be at the top of our favorite fish to chase here in Iowa. March begins the Walleye spawning run in many rivers and lakes, tempting fishermen and women out of hibernation to chase after them just after ice-out. Musky…the elusive yet hard fighting predatory fish dubbed “the fish of ten-thousand casts,” has quite the following in Iowa. Many of Iowa’s anglers often head to northern reaches to chase after both of these fish; however, the Iowa DNR and the Fisheries Bureau have made great strides and have worked to produce quality musky fishing in other parts of the state.

In cooperation with the Central Iowa Anglers, Recycled Fish, The Iowa DNR, and the U.S. Army Corps of Engineers, a fish barrier was installed on the Big Creek spillway in 2012 to minimize Walleye and Muskellunge escapement and improve fishing in Big Creek. In 2016, the Iowa DNR Fisheries Bureau and Iowa State University applied for and received funding through the Planning Assistance to States & Tribes Program from the Corps to evaluate the effectiveness of the fish barrier for reducing Walleye and Musky escapement.

In the spring of 2016, Iowa DNR Fisheries Biologist Ben Dodd and other DNR staff were at Big Creek Lake electrofishing for Walleye and Musky. “We are tagging these fish and releasing them back into the lake,” said Dodd. These PIT tags, as they are known by the IDNR (similar to microchips that veterinarians provide pets), are implanted into the fish, which are then released. “The purpose of the tags is to individually mark the fish and determine if they escape through the fish barrier,” he added. “At the time of tagging, we are also gathering information such as length, weight, and sex, which we can match up to the tag numbers of individual fish. Brushy Creek Lake was used as a control lake for the study because it’s similar in size, Walleye and Muskellunge escapement has been documented there, but it lacks a barrier. The DNR installed automated PIT tag readers at the Big Creek and Brushy Creek spillways, which record PIT-tagged fish that escape over the spillway.

The second part of the project assessed fish escapement using radio telemetry, which involves implanting radio tags in and tracking both Walleye and Musky

in Big Creek and Brushy Creek. This part of the study was implemented by Iowa State University Research Assistant Robert Weber. “The telemetry study will help us determine what habitats the fish are using seasonally and how much they move during different times of the year,” according to Weber. The telemetry study will also provide information about how water temperatures and flows are related to fish escapement; this, in turn, will help provide a better understanding of when these fish are prone to escapement.
Additionally, Robert tagged juvenile Walleye and Musky to study their behavior and determine if they were more or less likely than adults to go over the spillway. “Altogether, these different tagging methods will help us better manage the system and improve the quality of these valuable sport fish,” he added.

Looking Ahead
The first five years of this study indicate that the Big Creek Lake fish barrier effectively minimizes Walleye and Musky escaping. “Escapement rates of tagged fish from Big Creek Lake were extremely low (<1%), indicating the barrier is effective at minimizing escapement,” Dodd said. For comparison, escapement rates were higher for Walleye (5 – 22%) and Musky (13 – 47%) at Brushy Creek Lake (the control lake without a barrier). These popular sport fish species are maintained in our reservoirs by hatchery rearing and stocking efforts, which can be costly. Further analysis of escaped PIT-tagged fish will provide more insight into the potential savings offered by this barrier design.

Radio-tagged Walleye and Muskellunge have exhibited large movements during the spring and fall while moving less during summer. Additionally, Walleye and Muskellunge demonstrated to have extensive annual ranges in both lakes, with most locations near spillways occurring during spring. The use of these areas by Walleye and Musky, combined with high flow events due to spring precipitation, could lead to the increased escapement. Data from radio-tagged Walleye and Musky has shown that the escapement of these fish is directly related to high water events.

The original project ended in 2020; however, there was a lot of interest in extending the project to gain additional knowledge regarding the impacts of the barrier bar spacing, fish movement, and habitat use and evaluate a new barrier at Brushy Creek Lake. “We began receiving calls from other state conservation agencies who were interested in installing a similar barrier at lakes they manage for angling,” added Dodd. Therefore, the Corps, the Iowa DNR, and Iowa State University will continue studying escapement at both Big Creek and Brushy Creek through the spring of 2022. The Iowa DNR installed a barrier at the Brushy Creek Lake spillway this past summer, which will allow them to compare the escapement of Walleye and Muskellunge before and after barrier installation. “We’ve observed an improvement in the Muskellunge and Walleye populations and the quality of angling for both species at Big Creek Lake, and we’re excited to repeat this success story at Brushy Creek Lake,” he added.

How You Can Help
You can be a part of the research team by doing your part, returning tags you find in harvested fish. “We would like to encourage anglers to assist by returning these tags to the IDNR when they find them,” continued the biologist. “We have signs posted near boat ramps at both lakes that inform the anglers about the project and what to do with those fish when they are harvested.” There are drop boxes, surveys, and envelopes at the fish cleaning stations and park offices at both lakes. He added that providing those tags and surveys lets the IDNR Fisheries Bureau know which fish are no longer in the system. “It also gets us the tag back in hand, which overall will help with project expenses,” adds Dodd.

Acknowledgements
This has been a collaborative project, so the Iowa DNR Fisheries Bureau would like to thank all of its partners, including the U.S. Army Corps of Engineers, Iowa State University, Central Iowa Anglers, Mid-Iowa Muskies Inc., Chapter 55, and Recycled Fish. In addition, they’d like to acknowledge the anglers and volunteers who have assisted with the fish collection for this project.

Iowa’s angling opportunities continue to improve year to year. Programs like the one we’ve featured here today are but one step in that direction. And as Recycled Fish reminds us, practicing C.P.R. (Catch, Photo & Release) and selective harvest are all part of the management system. Tight lines all!