Improving Walleye and Muskie Fishing In Iowa: Part 2

By Ben Leal

In the spring of 2016, we featured a very similar article discussing how the Iowa Department of Natural Resources, the U.S. Army Corps of Engineers, and researchers from Iowa State University were working on improving the walleye and muskie fishing in Iowa.

“We observed a significant loss in Muskellunge abundance in Big Creek Lake from 2007 to 2010. This loss seemed to coincide with flood events during their spawning period over several years,” said IDNR Fisheries Biologist Ben Dodd. “In addition, we were researching harvests in 2010/2011 at Big Creek, by tagging fish and releasing them back into the lake; of those two tagged fish that were caught downstream. One was caught below the Saylorville dam in the tailrace and the other was caught up at the big dam at Fort Dodge.” At that point, the IDNR fisheries biologists began researching fish barriers and finally settled on a physical barrier that consists of horizontal bars. The barrier was installed in 2012 with assistance from Central Iowa Anglers, Recycled Fish, the IDNR and the U.S. Army Corps of Engineers.

Dr. Michael Weber (Iowa State University) and the Iowa DNR Fisheries Bureau applied for and received funding through the Planning Assistance to States & Tribes program from the Corps. The IDNR is collaborating with Dr. Weber’s lab and the Corps to evaluate the effectiveness of the Big Creek spillway fish barrier at reducing walleye and muskellunge escapement.

“We are tagging walleye and muskie and releasing them back into the lake”, said Dodd. These PIT (passive integrated transponder) tags as they are referred to by the Iowa DNR (similar to microchips that veterinarians provide pets) are implanted into the released fish. “The purpose of the tags is to individually mark the fish and to see if they escape through the fish barrier”, he added. “Before we tag them however we are gathering information on each fish such as length, weight, and gender. All that information is then recorded to coincide with the tag number being implanted.”

The DNR installed automated PIT tag readers at the Big Creek Lake and Brushy Creek Lake spillway in late winter/early spring in 2016. Brushy Creek Lake is being used as a control lake during this project because it is similar in size and walleye and muskellunge escapement has been documented there and it has no barrier.

“The tags monitor each individual fish and will let the IDNR know when a fish has gone over the spillway”, he continued. “These readers are set up behind or downstream of the barrier, if a fish goes through the barrier it gets detected, its fish tag number is recorded.” This study design will provide a means for comparison between a lake that has a barrier (Big Creek) and a lake that does not (Brushy Creek).

Radio Telemetry
Radio-telemetry is also being utilized to monitor habitat use, movement and to determine what factors influence escapement of walleye and muskellunge.

2018 Update
“In general, the study is going pretty well”, said Dodd. “We’ve got a two-part study going, one is escapement with PIT tags and the other is seasonal movement and habitat use of walleye and muskie using radio telemetry”. This is the third spring that the fisheries management team has been doing their tagging with the 2018 sampling and tagging being the second full spring. Managers have implanted 32 mm HDX PIT tags into 4000 walleye and 640 muskellunge at Big Creek and nearly the same number of tags into Brushy Creek fish. Preliminary results indicate that the barrier is effective at reducing fish loss at Big Creek Lake. Since mid-April 2016, 170 tagged walleye and 25 tagged muskellunge have been lost from Brushy Creek, where only 13 tagged walleye and 5 tagged muskellunge have been lost from Big Creek.

“A total of 85 walleye and 45 muskellunge are currently being tracked with radio telemetry between the two lakes”, said Iowa State University Research Assistant Robert Weber. Radio-tagged walleye and muskellunge in Big Creek have been found to move least during the summer, with most movement occurring during the spring and fall for both species. Both walleye and muskellunge were found to have larger seasonal home ranges in Big Creek than in Brushy Creek.

At Brushy Creek, muskellunge and walleye home range sizes were comparable across seasons, and the minimal movement of these fishes may be due to the abundance of coarse woody habitat and aquatic vegetation within the system. “In 2017, 35% of radio-tagged walleye in Big Creek and 20% of radio-tagged walleye in Brushy Creek were harvested by anglers and returned, with most of the harvest occurring from April to June,” added Weber. “No radio tagged fishes have been lost over the spillway at Big Creek. However, 8% of radio-tagged muskellunge and 15% of radio-tagged walleye escaped from Brushy in 2017. An additional 14% of radio-tagged walleye have escaped from Brushy Creek so far in 2018.”

Looking Ahead
“We’re right in the middle of the five-year study”, continued Dodd. “We’ll be sampling in the spring of 2019 and then again in the spring of 2020, where we’ll be done with the tagging and follow the fish for the remainder of that year.” The goal is to determine what’s causing these fish to go over the spillway, is it flow, the spawning period, or a combination of these two factors? “We’re looking at several environmental variables to determine what leads to escapement of both walleye and muskie”. The Iowa DNR will also be looking at different barrier designs in a lab environment at the Rathbun hatchery to test various spacing of the horizontal bars and other barrier designs with the ultimate goal of choosing a design that is both cost-effective and efficient in preventing escapement from Iowa’s impoundments.

“The overall objective of the study is to evaluate the effectiveness of the barrier at Big Creek versus Brushy Creek that does not have one”, adds Weber. “The telemetry study will help us determine what habitat the fish are using seasonally and how much they move during those seasonal changes.” The telemetry study will also help relate water temperatures and flows to fish escapement which will help with a better understanding of when these fish are prone to escapement. “It also helps us determine if it’s the juvenile fish or the adults are more likely to go over the spillway and in general will help us be better prepared to manage the system and keep them in the fishery.”

How You Can Help
You can be a part of the research team by doing your part, returning electronic tags that you find in harvested fish. “We would like to encourage the public to help by returning these tags to the IDNR when they find them”, continued the biologist.

“We have signs posted at the boat ramps at both lakes that inform the anglers on 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 by providing those tags and surveys it lets the IDNR fisheries management team know which individual fish is no longer in the system. “It also gets us the tag back in hand, which overall will help with project expenses”, adds Dodd.

Acknowledgements
Mid-Iowa Chapter of Muskies Inc. joined the research project by volunteering and providing 1,200 PIT tags for tagging muskellunge. “We would like to thank all of our partners and volunteers for their help on this project”, acknowledged Dodd. “It’s been a pleasure working with folks who are so passionate about Iowa’s resources.

There’s nothing quite like seeing a trophy walleye or musky come out of some of Iowa’s local fisheries. The Iowa Department of Natural Resources is working hard for you, the angler, to improve these fisheries for not only you but for future generations to enjoy. Take someone fishing, young and old alike, and share your love of the sport. Remember that we are all responsible for the stewardship of not only our local fisheries but lakes, rivers, and streams across the country where we might fish. All of these resources are for you to use…pass them along in better shape than you found them. Do something today…give them tomorrow. Tight lines all!