Southern Division Project Spotlight: Fisheries Management from the Ground Up
By Nick Feltz, FMS Southern Division Representative, Fisheries Management Biologist with Arkansas Game and Fish Commission
Temporary dewatering of a reservoir is a common practice in the Southeastern US that is initiated to achieve a variety of objectives that typically include infrastructure maintenance, nuisance species control and habitat enhancement. Extended dewatering of a reservoir provides opportunities that would otherwise be impractical to pursue.
Repairing or replacing a water control structure is most efficiently achieved with an empty reservoir. Reestablishing a fish population by eradicating the existing population is a highly effective management tool for producing above average growth rates, a more desirable species composition, or augmenting genetic composition of gamefish such as largemouth bass. Eradicating an existing fish population is only practical if available surface area of water is reduced to a few acres or less. Dewatering a reservoir and exposing the lakebed can improve substrate composition for fish spawning, produce a large biomass of vegetation for fish habitat, and stimulate the natural cycling of nutrients within the ecosystem. Dewatering also provides management biologists with the conditions to actively enhance habitat. Excavation of the lakebed to produce a more complex bathymetry, addition of a diverse variety of substrates, and installation of complex habitat structures made of wood, concrete, or artificial materials can increase the amount of available quality fish habitat.
Two reservoirs, approximately three hours apart in central Arkansas and Northeastern Mississippi, currently look more like a prairie grassland or even a desert in some parts, than a reservoir. Both saw the beginning of major dewatering in 2023, but under vastly different circumstances and reasons.
Lake Conway, an Arkansas Game and Fish Commission owned reservoir built primarily for fishing and hunting in Mayflower, Arkansas, is an integral part of the most populous part of the state and improvements to the reservoir were viewed as in investment in the community. Dam replacement and modernization, improving boating access through the maze of stumps and bank angling opportunity, and enhancing habitat are the primary objectives of the project (Figure 1).
Arkabutla Lake, a U.S. Army Corp of Engineers owned reservoir near Hernando, Mississippi, just south of Memphis, Tennessee, is managed for flood control and began its dewatering under slightly more urgent circumstances. The primary objective is to make critical repairs to the dam (Figure 2).
Despite these reservoirs having different primary purposes and the projects having different primary objectives, they do share things in common. Both reservoirs are much larger (6,700 acres and 11,200 acres) than the typical small impoundment (<1,000 acres) project and therefore present unique challenges to a fisheries management biologist. Everything from the dewatering process to actually completing project objectives is at a bigger scale and naturally takes longer. Many of the typical aspects of a dewatering project such as eradicating the existing fish population and sediment excavation work are impractical. The longer timeline on a larger reservoir presents brand new challenges. Vegetation transitioning from beneficial habitat to woody nuisance species that become future navigation problems. Completing habitat enhancement work in difficult to access locations of the reservoir. Managing public access to the lakebed, treasure hunting, and looting of Native American artifacts.
These much larger reservoirs, residing near populous areas, adds to the number of people that are impacted by these projects and their scrutiny. Effectively communicating our science and objectives quickly become key aspects of the overall project. Encouraging and assisting lakefront property owners to take advantage of the dry conditions and make their own improvements while navigating difficult conversations with people that are grieving the temporary loss of perhaps their favorite place to get away from all the chaos. There are certainly sacrifices being made by the people that use these places, but rest assured, fisheries biologists have been executing and refining these types of projects for decades and if history tells us one thing it is that both these fisheries will be back and better than before.