With a median age of nearly 70 years, reservoirs in the USA are showing compelling signs of fish habitat degradation, particularly in littoral areas. To rejuvenate these fish habitats we are researching the establishment of agricultural plantings on reservoir mudflats. Several agricultural plant species commonly used for wildlife food plots were selected for planting based on their ability to grow during winter and under diverse soil quality conditions. Over the course of two weeks in October, 2016 and 2017, we established 30-40 experimental plots each year by disking and seeding approximately 50 acres of exposed shorelines using ATV-towed seeding implements. Success of establishment was evaluated with surveys conducted monthly throughout the following winter and into spring.

In the 2016-2017 growing season, two grass species, ryegrass and triticale, performed well in mudflats despite poor soils with acidic pH. Ryegrass excelled in ground cover and biomass, and triticale in maximum height. These complementing features contribute to diversity of fish habitat structure. In general, forbs (grasses) performed better on mudflats than legumes (clovers), or than legume-forb mixed plantings. However, the 2016-2017 fall-winter period was unusually dry potentially hampering plant growth, so further evaluation is needed.

In the 2017-2018 growing season, repeat species from the previous season as well as new test species had become established by January 2018. However, excessive rainfall in February 2018 prompted the USACE to raise water level ahead of schedule. Consequently, our crops were submerged before they could attain full size and we were unable to evaluate growth or benefits to fish.

During our study, evaluation of ground cover in mudflats has been hampered by unpredictable water levels. In Spring 2017, because of below average rainfall, reservoir water level did not reach normal pool, which allowed plant growth but precluded evaluation of plant benefits to fish. Conversely, in Spring 2018, excessive rainfall flooded crops before they could attain full growth and several weeks before the spawning season. Therefore, in our second season we were able to evaluate neither plant growth nor benefits to fish. Consequently, we have extended this evaluation into a third year. In October 2018 we will re-plant the study area and repeat the evaluation under the expectation of a normal water level year. Our results so far suggest that selected plant species grow well in mudflats, but growing crops in reservoirs with highly unpredictable water levels has risks that in many cases may not be permissible.

After flooding terrestrial plants start to degrade, their persistence under water can determine value as fish habitat. Persistence of terrestrial plants after inundation was evaluated in experimental tanks. We submerged various plant species for over 3-month to simulate the length of time mudflats are flooded in Enid Reservoir. Legumes showed major degradation in the first few weeks, whereas forbs retained adequate structure over several months. Mature ryegrass and triticale may provide adequate structure for fish for the entire flooding season. Ryegrass lost stems and produced large gaps among vegetation and thus may produce suitable adult fish habitat. Triticale remained dense and complex and thus may support suitable juvenile fish habitat.

Fish attractors such as brush piles have often been placed in reservoir mudflats to provide habitat diversity and cover for fish. However, their performance has remained mostly unevaluated. An evaluation would benefit existing fish attractor programs supported by our cooperators (i.e., MDWFP, USACE, RFHP, and USFWS). Thus, to fully use available resources committed to this research we switched our scheduled evaluation of fish in planted plots to an evaluation of installed fish attractors. In early 2017 the USACE in cooperation with local fishing clubs established nearly 200 fish attractors (brush piles) in our study site. We used rotenone to sample 120 sites with and without (control) brush piles, in May-September, 2017. Abundances of juvenile fish and their average size differed. Three species, bluegill, largemouth bass, and black crappie showed higher abundance in brush piles as compared to control sites. Juvenile fish in brush piles were larger than those in control sites during a majority of the sampling season. We also detected differences in fish association with brush piles in relation to pile size and depth location. Increasing the percentage of brush within a reservoir increases the density of juveniles of selected species and bring densities closer to levels seen in naturally-vegetated lakes, or in flooded wooded areas of the riparian zone.

In the upcoming year we plan to replant the mudflats in October, monitor plant growth through fall, winter, and early spring, and estimate fish and invertebrate benefits in late spring and early summer. We will also be completing a tank study designed to asses