Evaluation of the Largemouth Bass Population Before and After Habitat Restoration at Suwannee Lake

man holding a fish

FFR administrator Jason Dotson holding a 4-year-old 8-pound bass collected at Suwannee Lake during the 2018 mark-recapture sampling.

Abundant aquatic resources are a defining characteristic of Florida. Our state encompasses approximately 7,700 lakes and ponds, many of which are subject to natural processes that lead to accumulation of sediment and organic material on lake bottoms. Over time, these processes can result in diminished habitats for fish communities. In northern Florida, Suwannee Lake was identified by local stakeholders as well as from annual monitoring that the quality of its fisheries and habitats had declined, likely owing to processes associated with aging reservoirs.

Beginning in 2011, staff from FWC’s Aquatic Habitat Restoration and Enhancements Section (AHRES) and Division of Freshwater Fisheries Management (DFFM) began collaboration on a five-year process of large-scale, whole-lake restoration at Suwannee Lake, while FWRI assisted with documenting changes to the fish community. The objectives of the restoration project were to improve habitat by scraping and removing accumulated muck, increasing deep-water refuge, adding variability to depth contours, and restoring the native aquatic plant community. Ultimately, through improved habitat and restocking, the goal was to re-establish quality fisheries, especially for largemouth bass.

The myriad benefits of large-scale lake-restoration extend to the entire lake ecosystem, but the effects are perhaps most visible to citizens and anglers through increased numbers and size of fish they catch. Lake restoration projects that drain lakes and keep the lake-bed dry for an extended period before reflooding can, perhaps surprisingly, produce a surge of nutrients and growth in the aquatic ecosystem. Nutrients previously bound in organic sediments oxidize during the dry period and become newly available to aquatic plants and plankton, fundamental parts of the aquatic food chain. Additionally, terrestrial plants and brush may grow across dry lake beds, becoming food and habitat for aquatic invertebrates after reflooding. These processes can result in a surge of energy and nutrients through the aquatic food chain, ultimately leading to improved fish populations, especially apex predators like largemouth bass. Many fisheries biologists and managers consider these processes conventional wisdom but are not well documented in the literature. A major goal of the fisheries component of the project was to document potential changes to largemouth bass populations as a result of enhancements.

In June 2013, the intensive process of emptying Suwannee Lake began, a process called dewatering. Heavy machinery was brought in for removal of accumulated, soft sediments and 60,000 cubic yards was removed from the lakebed. Additional sediment was scraped and repurposed into offshore islands. Existing submerged woody debris was conserved and reorganized into complex, offshore aggregations. Just prior to reflooding, thousands of native plants such as bulrush, maidencane, and cypress trees were strategically planted.

  • Lake after draining

    Suwannee Lake after the process of draining.

The restoration project and de-watering of Suwannee Lake allowed FWC biologists the opportunity to hit the “reset button” on the lake’s fish community. As the lake refilled, they were afforded the opportunity for precise control of the timing, quantity and species of newly-stocked fish. Sunfish species such as bluegill (Lepomis macrochirus) and redear sunfish (L. microlophus) and forage species such as Threadfin Shad (Dorasoma petense), Lake Chubsucker (Erimyson succuta) and Golden Shiner (Notemegonas chrysolucas) were stocked during fall 2014. Last, as apex predator in the fish community, fingerling Florida-strain largemouth bass were stocked in spring 2015.

man on boat with net

A biologist nets bass during mark-recapture sampling at Suwannee Lake in 2013.

FWRI and DFFM biologists partnered in monitoring the fish community at Suwannee Lake before and after the restoration project to document its success. Specifically, FWC is monitoring the lake’s largemouth bass population and measuring key characteristics of the population through time. Researchers used electrofishing to collect bass, and the bulk of the sampling was focused on two multi-event, mark-recapture population estimates for lake-wide abundance of largemouth bass before and after the restoration (2013 and 2018). Additionally, researchers recorded length and weight for all bass collected to evaluate any changes in size or condition. This process was repeated six times over a month in the spring of 2013 and 2018.

The abundance of largemouth bass in Suwannee Lake doubled from 2013 (pre-renovation) to 2018 (post-renovation). In 2013, FWC estimated that the lake held 1,875 bass one year or older; in 2018 there were an estimated 3,800 bass. The mean weight of bass increased from 376 grams in 2013, to 501 grams in 2018; mean length of bass increased slightly from 283 mm in 2013, to 304 mm in 2018. Additionally, eight unique bass were sampled that were 8 pounds or heavier during the 2018 mark-recapture sampling. “One of the most fascinating things to observe in this project has been the extraordinary fast growth of some of the largest bass. Florida is known for big bass, but we very rarely observe bass that add weight at 2–2.5 pounds per year, as we have at Suwannee Lake,” said Andrew Dutterer, a lead researcher with this project.

FWC biologists plan to conduct at least one more mark-recapture population estimate (likely in 2020) to capture a more mature largemouth bass population post-renovation. They will also continue monitoring the entire fish community via annual sampling to understand the persistence of lake renovation effects within fish populations. FWC hopes to apply new, non-lethal aging techniques to bass at Suwannee Lake in the future, which allows for more detailed assessment of age and growth of the species without requiring the sacrifice of the fish.

This project demonstrated that following a large-scale lake restoration doubled the population abundance of largemouth bass and led to faster growth. Large scale habitat renovations like what was done at Suwannee Lake are expensive, take time to complete, and stakeholders lose the use of their resource while the renovation is being done – they are investments. However, Suwannee Lake is now a healthy and robust fishery for the Florida largemouth bass, and the positive results gained from sampling speak for themselves. Projects like this serve the important function of documenting the beneficial effects of large-scale lake renovation efforts at Suwannee Lake and elsewhere. A successful fishery is composed of three parts: habitat, fish and people. After the successful restoration of Suwannee Lake, all three have been revitalized.