Iowa Walleye Challenge Helps DNR Biologists Assess Their Walleye Fisheries

The Iowa Walleye fishery is an important recreational fishery in the state, stocking more than 160 million walleye in over 80 waterbodies every year. The program requires significant staff resources to collect brood stock, supporting the hatcheries and then release the fish. One of the challenges faced by walleye managers is assessing how well the stocked fish are doing, due to the high cost of conventional survey techniques. To help address this issue, MyCatch teamed up with the Iowa Department of Natural Resources in 2022 to test if a statewide walleye event could be used to help provide managers with better information on the state of the walleye fishery.

BACKGROUND

In 2020, MyCatch started running catch-photo-release tournaments on the mobile app as a way to attract competitive anglers to the platofrm during Covid. This update also allowed MyCatch to improve the quality and quantity of data reported through the app, and greatly expand the research capabilities of the app. This has opend the door for a wide range of new research activities where fishery managers and researchers can collaborate with anglers to address fisheries issues. The Iowa Walleye Challenge represents the first application of the tournament model to address a specific management challenge.

SETTING-UP FOR SCIENCE

To make these events useful for management purposes requires some modifications to a conventional tournament — specifically that all fish need to be reported and we need to know when an angler does not catch any fish. To achieve this goal, two incentives were built into the event:

1. A Most Fish Caught prize was awarded each week, incentivizing anglers to report every fish they caught. This allowed full length distributions to be captured, and not just the biggest fish.
2. A Tough Luck prize was issued to anyone who started a trip but did not report anything. This allowed us to capture the zeroes — an important piece of information for biologists.

With these incentives in place (along with the standard rules around accurate catch reporting), the event could start collecting data for management purposes.

RESULTS

The event ran two months (May 1 to June 30, 2022) and had 70 anglers participating, taking 551 trips and catching 2,074 walleye from 41 waterbodies. Big Creek Lake proved to be the most popular lake, with 114 trips reported, followed closely by Clear Lake with 110 trips reported. These two waterbodies represented the two most popular lakes in the state by a wide margin. Four maps are presented below that highlight the distribution of anglers, fishing trips, fish caught and places where no fish were caught across Iowa during the event.

WATERBODY ANALYSIS

Below is a histogram of fish lengths caught in Big Creek Lake. A total of 510 fish were caught (and released) in this lake during the event from 21 anglers taking 114 trips. The young age class is immediately visible in the 9-10″ range. A few big fish are caught at 26″-27″, but most are between 14-18″.

MANAGEMENT

From a management perspective, it is always good to compare the results of the event with other standard fisheries tools, such as creel surveys, netting surveys and electrofishing surveys. Initial work on this has started, and we anticipate being able to expand this article once the results have been finalized.

If anyone is interested in learning more about this project, please contact Sean Simmons by email ([email protected]).