Interior Rivers and Streams Research Team

Stream habitat is a key factor influencing the health of stream fish populations. Iowa’s river and stream fish resources have been greatly impacted by habitat degradation. Concerned with the continued degradation of river and stream habitats and fisheries, Iowa resource managers are interested in using stream rehabilitation practices to effectively improve these resources. This study began in 2010 to evaluate Iowa river and stream rehabilitation practices, and develop management guidelines to improve river and stream habitat, as well as fishing opportunities for Iowa anglers.

The first project being evaluated is the modification of the Vernon Springs Dam on the Turkey River at Cresco. The dam was converted into a series of rock arch rapids in late July 2010 to address safety and fish passage concerns. Pre-construction fish community and habitat sampling was done at three sites above the dam and two sites below. Over 3,900 game and non-game fish were marked below the dam to monitor fish movement over the new structure. Fish community and habitat sampling was also done at three sites on the Volga River to serve as control sites for the three upstream sites on the Turkey River. Post-construction sampling upstream of the project found 16 Black Redhorse, 11 Golden Redhorse, 3 Walleye, and 1 Northern Hog Sucker that moved upstream over the structure. Smallmouth Bass and Black Redhorse were sampled post-construction above the dam at sites on the Turkey River and N. Branch Turkey River where they were not found pre-construction.

Pre-project fish and habitat data were collected in 2012 and 2013 for a dam removal on the Shell Rock River in Rockford. The dam was removed in the winter of 2014 and four years of post-project sampling have been completed. Golden Redhorse and Northern Hog Sucker were collected for the first time at sites above the dam in 2014, and increasing numbers of these species were found upstream in 2015, 2017, 2018, 2019 and 2021.

Channel Catfish numbers also increased at sites above the former dam. The project has restored riverine habitat in the former impoundment and improved the fish community (increased number of species, adult Channel Catfish abundance, and Smallmouth Bass abundance). Habitat conditions in the former impoundment are similar to the downstream site and the upstream control site in terms of stream width, mean depth, mean water velocity, and substrate composition. Dam removal negatively impacted downstream habitat initially, but habitat conditions largely recovered within 3-4 years post removal.

A whitewater park and habitat improvement project was completed in spring 2015 at the site of the Marion Street Dam on the Maquoketa River in Manchester. Pre-project fish and habitat sampling was done at sites upstream and downstream of the dam in 2012-2014. Over 19,600 fish of 19 species were marked downstream of the dam to monitor fish movement over the new structures. Sampling in 2015-2021 found 826 marked fish representing 12 species that had moved upstream over the structures. Continued monitoring of these projects and investigations of additional stream rehabilitation projects will help guide future decisions and lead to improved methods, designs, and sharing of resources to improve Iowa’s river and stream fisheries.

Interest in modifying and removing aging, low head dams on Iowa’s interior rivers has increased over the past several years. This interest is driven by safety/liability concerns, deterioration of existing dams, and a desire to increase river recreation opportunities. Areas below dams often are popular fishing spots. A common concern is that removing or modifying a dam will negatively impact angling, particularly below the dam. The impact of removing or modifying a dam on angling has not been studied in Iowa, and little information is available from other states.

A whitewater park and habitat improvement project was completed in spring 2015 at the site of the Marion Street Dam on the Maquoketa River in Manchester. The dam was removed and six structures were built to create whitewater features, while also letting fish to pass upstream. The project was expected to improve angler access and fish habitat at the site. A roving angler survey was started in April 2012 to collect pre-project data on angler use, catch, and harvest on the Maquoketa River upstream and downstream of the dam. The survey also assessed other recreational uses like boating, tubing, and swimming. The survey was conducted in April-October for three years before and three years after construction. Total fishing effort (angler hours) was variable ranging from 4,232-6,797 pre-project and 3,770-7,597 post-project, and average fishing effort was similar before (5,267) and after (5,180) project construction. Average catch rates (number of fish/hour) were also similar before (1.47) and after (1.64) project construction, and varied annually from 1.14-1.95 pre-project and 0.92-2.56 post-project. Hours spent on the river by other recreational users in June-August averaged five times higher overall and 20 times higher in the project area during the post project period. Despite this significant increase in other recreational uses, our study found that angler effort and catch rates before and after construction were not significantly different and angler satisfaction has increased.

Measuring the impacts of removing or modifying a dam in Iowa will provide information to help managers address angler concerns with future projects. This information may also help identify project features which benefit anglers that can be incorporated into future projects.

Walleye fingerling stocking has greatly increased Iowa’s interior river Walleye populations over the last 20 years. This has created an increasingly popular fishery that has brought Walleye fishing opportunities close to home for many Iowa anglers. The success of this program has also increased demand for two inch long, Mississippi River strain Walleye fingerlings. Limited hatchery space has made it difficult to consistently produce enough fingerlings of the size and genetic strain requested for the program. Providing information needed to more efficiently use our limited hatchery production capacity, and exploring the potential of other fish culture systems to meet the demands of the river Walleye program is the focus of this study.

Available pond culture space has been a limiting factor for producing Mississippi River strain fingerling Walleye to stock in interior rivers. Recent research at the Rathbun Fish Culture Research Facility has shown promising results raising Walleye fingerlings using an alternative method, intensive fry culture. Intensively reared walleye fry are stocked into recirculating tanks and trained to eat formulated feed from day 1 post-hatch, instead of stocking them into ponds where they eat zooplankton (extensive culture). Evaluating the relative contribution of intensively reared fingerlings to interior river Walleye fisheries will determine if this production method could help further improve river Walleye fisheries.

Study sites were selected on four Iowa rivers to evaluate the contribution of intensively reared Walleye fingerlings to interior river Walleye populations. Extensively reared fingerlings were marked, hauled, and stocked alongside intensively reared fingerlings to serve as a control. Walleye fingerlings produced by this culture method are known to survive and contribute to river Walleye fisheries if river conditions are favorable. Intensively cultured Walleye fingerlings were marked with a circle freeze brand, and extensively cultured fish were marked with a bar brand. Over 61,000 marked intensively and extensively cultured walleye fingerlings were stocked in the Wapsipinicon, Maquoketa, Shell Rock and Cedar rivers in June 2016. Study sites were sampled during late-September and October to determine survival and growth of walleye fingerlings. This process will be repeated for several years. The results will help guide Walleye fingerling production and stocking methods to provide the greatest benefits for sustaining and improving Walleye fisheries in Iowa rivers.

Wild trout have played an increasingly important role in trout management in Iowa over the last 20 years. Recent increases in self-sustaining trout populations have expanded and diversified opportunities for Iowa anglers to pursue trout. A major factor in this increase is the use of fingerling stocks derived from wild and local parents to establish wild trout populations in other streams. Fisheries managers have had great success establishing self-sustaining populations of non-native Brown Trout by stocking fingerlings of French Creek origin. This has diminished the need for hatchery production and stocking of this popular species, and provided new recreational fishing opportunities for Iowa trout anglers. Self-sustaining populations of Brown Trout have expanded so rapidly in Iowa that their full extent is currently unknown. Wild populations of native Brook Trout have also been successfully restored to several northeast Iowa streams by stocking fingerling Brook Trout of South Pine Creek origin.

The South Pine Creek Brook Trout population provides a limited resource for propagation of fish for stocking, so it is important that restoration stocking is done on streams where there is the greatest probability that Brook Trout populations will be successfully established. The recent expansion of wild Brown Trout populations in northeast Iowa has raised concerns for fisheries managers, due to potential negative impacts of the species on Brook Trout restoration efforts. It is important to know the distribution of wild Brown Trout populations for managing Brown Trout populations and planning wild Brook Trout restoration efforts.

The goal of this project is to assess the status and distribution of Brook Trout and Brown Trout in northeast Iowa, and identify cold water streams where wild Brook Trout restoration has a high probability of success. Our general approach is to identify likely cold water streams using winter satellite images taken during very cold periods to find stream reaches that do not freeze over and are likely to have good cold water spring flow. We then select sites from these likely cold water reaches where we can sample fish and habitat conditions.

We have sampled 20 sites in four sub-watersheds of the Upper Iowa River. Brown Trout were sampled at 16 of these sites. Brook Trout were sampled at one site, and a Brook Trout X Brown Trout hybrid was sampled at one site where Brown Trout were also collected. The four sites where no trout were collected had the lowest stream flows (<0.2 cubic feet/sec) of our sample sites. Several sites identified from winter satellite imagery were either completely dry, or had very limited spring flow which was not sufficient to support fish during late summer. Conditions at 15 of these sites were documented with georeferenced photographs of dry reaches, beginning and end points of reaches with water, barriers to fish movement, and spring sources. This information will be used to help further refine site selection using remote imagery.

• Evaluation of Importance of Specific In-Stream Habitats to Fish Populations
• Evaluation of the Status, Distribution, and Habitats of Flathead Catfish in Iowa’s Rivers