Large River Research Team

Walleye and sauger support popular and important fisheries on the Upper Mississippi River bordering Iowa. Walleye continually rank high in angler catch and harvest in summer pool wide and winter tailwater angler surveys. Saugers are the majority of fish caught and harvested at tailwaters fisheries from October – March. This study was started because of concerns with high sauger death rates, highly variable reproduction in Walleye, and the desire to maintain and improve these important fisheries.

Concerns with deep water post-release hooking deaths of Sauger led to a study completed in 2012. Sauger were caught from the tailwaters of Guttenberg and Bellevue and held in a deep-water net pen to measure 72-hour death rates. Overall, hooking deaths was 18%, but rates increased with depth. Death rates were 7% for Sauger caught from depths of 20-29 feet, 17% from 30-39 feet, 25% from 40-49 feet, and 41% from 50 feet or greater. Sauger length was also found to be inversely proportional to depth. Larger Sauger were caught on average at shallower depths than small Sauger. Tailwater anglers can use this information to decide where they should fish. Fishing in deep water yields small Sauger; a large proportion of released fish will likely die. Fishing in shallower water yields larger fish and a greater proportion of released fish will survive.

Walleye reproduction on the Upper Mississippi River is highly variable with boom and bust years. Increasing and stabilizing reproduction would improve the consistency of the fishery. Seventy percent of Walleye eggs come from 20-27 inch fish. Protecting this size class to increase the number of eggs in the system may improve future reproduction. In 2004, a 20-27 inch release slot limit was started from Lock and Dam 11 in Dubuque to the Missouri border. Evaluation of the Walleye slot limit has shown an increase of 20-27 inch Walleyes in pools where the regulation is in effect (Pool 13) versus pools without the regulation (Pool 11). While proportional stock density (% fish > 10” that are > 15”) was high at both Pools 11 and 13 (78 and 90 respectively), the percent of Walleye over 20 inches was only 15 in Pool 11 compared to 44 in Pool 13.

Night electrofishing is done each October in the tailwaters of Pools 11 and 13 to measure Walleye and Sauger year class strength. High water levels have not allowed us to effectively sample the past few years. Surveys in 2016 showed weak Walleye and Sauger year classes at Bellevue (Pool 13) and Guttenberg (Pool 11); high water levels during sampling likely negatively affected catch rates. There are good numbers of 14-inch and larger Sauger available, so anglers should have good success in the tailwaters this winter and spring. The slot limit regulation appears to have been highly successful so far, yet future work on this project will continue to measure the effects of the slot limit on Walleye reproduction.

Fish telemetry has provided proof that the availability of overwintering habitat is a limiting factor for Centrarchid (e.g., Bluegill, Crappie and Largemouth Bass) populations in the Upper Mississippi River (UMR). Centrarchids traveled long distances (> 3 miles) to reach suitable overwintering backwater areas with low current speeds, water depth > 1 m, water temperatures 1-3° C warmer than the main channel, and adequate dissolved oxygen levels. Lock and dam construction in the 1930’s greatly increased the total aquatic area of the UMR and provided deep backwater areas favorable to Centrarchid populations; but, sediment deposition in backwaters has reduced the quantity of deep-water lentic habitats. As the post-impoundment UMR ages and backwater sedimentation continues, abundance of Centrarchids will likely decline unless management actions are taken.

The Iowa Department of Natural Resources works collaboratively as part of the partnership of state and federal agencies that make up the Upper Mississippi River Restoration - Environmental Management Program. Many Habitat Rehabilitation and Enhancement Projects (HREP) are designed to increase sportfish populations important to Iowa anglers. Multiple HREPs have specifically focused on mitigating effects of backwater sedimentation through sediment dredging, restoration of aquatic connections between backwater and channel areas, and installing control structures that let oxygen-rich channel water enter into backwaters areas during periods of low dissolved oxygen. Research has documented positive effects of HREPs on Centrarchid populations in backwater habitat and identified habitat variables (e.g., dissolved oxygen, velocity, and depth) critical to Centrarchids.

Despite our understanding of the benefits of overwintering HREPs, many questions remain. For example, we do not know how many or at what interval overwintering areas are needed in a pool to keep Centrarchid populations healthy. Information is lacking on the best size of an overwintering backwater and the “sphere of influence” for an individual overwintering backwater (i.e., area of the pool inhabited by fish from an individual overwintering backwater during the rest of the year).

By better understanding overwintering requirements of Centrarchids, we can ensure enough winter refugia is available to sustain a viable sunfish and bass fishery. There is also much to learn from studying newly constructed HREPs to ensure project features function as designed. While backwater restoration has received much attention on many projects, other habitat restoration techniques such as island construction, side-channel restoration, and bankline stabilization present future study opportunities as well. Evaluation of different HREPs and restoration features will provide information on which techniques are most beneficial to riverine sport fish populations.

This study, started in 2014, will help us gain a greater understanding of these questions and lead to improved efficiency and success of future overwintering habitat project design and placement.

Yellow Perch provide important and popular sport fisheries across their range. Yellow Perch in South Dakota are listed as the second most popular sportfish in the state, with several lakes in North Dakota and South Dakota receiving national attention for their recreational Yellow Perch fishing.

Yellow Perch have been documented in creel surveys within the Upper Mississippi River, ranking anywhere from the 7th to 9th most popular sportfish. It was also reported that Yellow Perch were only a minor constituent of the ice fishing catch from several backwaters in Pools 9 and 10; but, based on the Long Term Resource Monitoring Element’s annual sampling from 1993-2018, Yellow Perch populations have increased for the past 10 years in Pools, 4, 9, and 13. Yellow Perch have become an important sportfish in some locations of the Upper Mississippi River, including within multiple completed Habitat Rehabilitation and Enhancement Projects (HREP). According to the most recent survey of Iowa anglers, Yellow Perch were the 3rd most popular panfish species, behind only Crappie and Bluegill; yet, only 8% of respondents said they had fished for Yellow Perch in Iowa in the past 12 months.

Historically, Yellow Perch fishing in the Upper Mississippi River in Iowa was only a minor component of those fisheries. Latent demand for Yellow Perch fishing in Iowa and recent population increases in the Upper Mississippi River may have created an opportunity for fisheries managers. But, despite understanding that this is a popular sportfish across its range and has the potential for increases in popularity on the Upper Mississippi River, there is limited information available on Yellow Perch in the Upper Mississippi River.

The objective of this project is to evaluate telemetry methodology and seasonal habitat use of Yellow Perch in the Upper Mississippi River. The findings from this research study could help with the development of more diverse HREPs, provide greater habitat diversity, and expand Yellow Perch fishing opportunities for anglers.

Iowa DNR regularly evaluates lake-based recreation to better understand how anglers and other recreational users use our public natural resources. Mailed surveys were conducted about lake-based recreation beginning in 2002, with the most recent survey in 2019. Unfortunately, mail-based survey response rates have been declining, so alternative approaches must be investigated before the next survey to get better information.

Evaluation of lake and reservoir recreation, especially fishing and boating, guides fisheries management in Iowa by establishing baseline expectations by lake type; highlighting key waterbodies in need of fisheries management action such as renovation; highlighting key waterbodies in need of protection and maintenance of stellar fisheries; measuring effects of renovations; and understanding the dynamics of visitation in socio-ecological systems. The objectives of this study are two-fold: 1) to evaluate historical data and understand any trends, and 2) to design the next survey to maximize effectiveness and data quality.

Creel surveys have been a valued source of fisheries information guiding management since the earliest days of formal fishery management in the U.S. In Iowa, creel surveys have been used for estimating fish population size, measuring impacts of fishery restructuring and habitat restoration, and determining the effectiveness of and compliance with fishing regulations. Creel surveys are also used for long-term fishery monitoring to determine overall catch, harvest, fish size, and angler satisfaction. In some cases, creel surveys have yielded long-term datasets at important fishing locations like Clear Lake, Spirit Lake, West Okoboji Lake and Rathbun Lake. Iowa DNR has consistently used an established method for analyzing creel data, but never had a standardized analysis tool.

The Iowa DNR must update its approach to standardized creel data collection, storage, and analysis. Without this effort, the current system could become defunct without warning and hinder ongoing creel surveys (e.g., if the data collection application stops working, or a Microsoft update alters the object library used by Access). Its difficulty for fisheries managers to access may reduce interest in conducting standardized creel surveys, resulting in a relapse to reliance on outdated, non-standard analytical tools.

Without developing a new tool with a more robust programming language, we are unable to improve upon or expand the analysis to align with current guidelines for creel surveys derived from the literature (Nieman et al. 2021; Lynch et al., in revision). The data collection and storage issues are already being addressed outside of the Sport Fish Restoration grant program, making developing an analytical tool compatible with the new system extremely timely.

This study will facilitate the continued standardization of quality creel surveys across Iowa by providing a useful tool for fisheries biologists. By making analysis and reporting easier, the tool will encourage biologists to conduct surveys following the standard design, analyze data using identical expansion and summary methods, and report findings in similar formats. Although in many ways, Iowa DNR staff have aligned with each other in methodology and much of their reporting for years, this analytical tool will automate that process, rather than forcing each biologist to accomplish the same work independently. This makes the creel survey analysis and reporting process more efficient, allowing biologists to spend more time on other work.

Shovelnose sturgeon are a long-lived, slow-growing fish native to Iowa's rivers. They are highly sensitive to overfishing, habitat loss, and other pressures, leading to population declines that take decades to recover. Recent summer sturgeon kills on the Des Moines River, with dead sturgeon numbering in the tens of thousands, has highlighted the need to assess and better understand our populations. Shovelnose sturgeon, one of the most ancient fish species in Iowa, support recreational fisheries on the Mississippi River and its major tributaries, including the Des Moines, Iowa, Cedar, Skunk, and Maquoketa rivers.

Population assessment involves monitoring shovelnose sturgeon populations each year, collecting information on growth and mortality rates, spawning frequency, spawning success and failure, and seasonal movements. During spring, we sample adult sturgeon using electrofishing and trammel netting during their spawning run, recording information and tagging all fish so we or anglers might re-encounter them later. Some fish are tagged with special tracking tags, which allow us to follow that individual's movement up and downstream using acoustic telemetry. We sample eggs and newly hatched sturgeon using tow netting, in hopes to improve our understanding of flow and temperature conditions that best support sturgeon reproduction.

• An Evaluation of Winter Habitats Used By, Bluegill, Black Crappie, and White Crappie in Pools 11-14 of the Upper Mississippi River (Summary)
• An Evaluation of Winter Habitats Used By, Bluegill, Black Crappie, and White Crappie in Pools 11-14 of the Upper Mississippi River (Full Report)
• Evaluation of the status, distribution, and habitats of Northern Pike in the Upper Mississippi River (Summary)
• Evaluation of the status, distribution, and habitats of Northern Pike in the Upper Mississippi River (Full Report)
• Assessment of Iowa's Shovelnose Sturgeon Sport Fisheries (Summary)
• Assessment of Iowa's Shovelnose Sturgeon Sport Fisheries (Full Report)