FWC Hydrilla Management Position Statement

Hydrilla hanging off of a boat motor

Hydrilla is a fast growing non-native aquatic plant.

During writing and review of the Florida Black Bass Management plan, the role of aquatic plants and their management was a frequent topic of discussion, especially hydrilla management. The Florida Fish and Wildlife Conservation Commission has made significant progress in developing and communicating these plans in the past year.

Hydrilla is a non-native submersed aquatic plant that arrived in Florida in the 1950’s. Since its introduction in south Florida it has spread throughout the state. This invasive exotic plant has been described as “the perfect aquatic weed” because of its tolerance to conditions that prevent other native plants from flourishing, including its tolerance of low light, high turbidity conditions and a wide range of nutrient conditions. Moreover, it can spread through fragmentation, stolons or rhizomes (rootlike structures), tubers that grow on rhizomes, or turions (another reproductive approach that forms in the juncture where leaves attach to the stems).  At low to moderate levels hydrilla can provide beneficial habitat for fish and wildlife. However, because many of Florida’s water bodies are relatively shallow, hydrilla has may become the dominant submersed plant in a very short time and can pose a complex challenge to resource managers.

What makes hydrilla management so complicated is that at low to moderate levels hydrilla can be a positive contributor to recreational fisheries and waterfowl populations, growing in areas or at densities not achievable with most submersed native aquatic plants. Fisheries biologists often suggest aquatic vegetation coverage of 20-40 percent should provide adequate habitat for largemouth bass populations. However, experience has shown that with peak summer growth rates hydrilla can quickly exceed beneficial levels requiring extensive and costly management. Hydrilla is not native to Florida and general conservation philosophies as well as the economics and logistics of attempting to manage it provide reasons to try to keep this plant out of new areas and keep it under control to prevent topping out, spreading and causing problems with navigation, flood control, potable and irrigation water supplies and affecting other forms of recreation and the aesthetic beauty of lakes. When aquatic plant coverage exceeds 60 percent studies have shown decreased growth rates and condition of largemouth bass.

In July 2008, the Department of Environmental Protection’s Bureaus of Invasive Plant Management (IPM) was legislatively moved to FWC Division of Habitat and Species Conservation. In April 2011, because of the challenges managing hydrilla the FWC Invasive Plant Management Section with input from the various FWC scientists developed an agency position statement that will guide the agency in managing hydrilla in the future MyFWC.com (search: Hydrilla Management Position).  The position statement provides a risk-based approach to use when planning hydrilla control. Additionally, stakeholder input is a key component of the hydrilla position statement and is needed to understand the desires of resource users. Recent work on the Kissimmee Chain of Lakes, Lake Istokpoga, Lake Apopka, Orange Lake, as well as other freshwater resources around the state have incorporated public input into annual hydrilla management plans. Division of Freshwater Fisheries Management staff will continue to work with IPM biologist and resource stakeholders for the future management of hydrilla throughout the state.

For additional fisheries information contact fisheries biologist Bill Pouder, 863-6448-3805; Bill.Pouder@MyFWC.com.

FWC Facts:
The largest lake in Florida is Lake Okeechobee.

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