Hydrilla — the 9-headed marsh serpent
Fish Busters' Bulletin
Friday, December 03, 2010
Media contact: Bob Wattendorf
In classic Greek mythology, the Hydra was a marsh
serpent that had nine heads to start with, but each time one was
cut off, two more grew back until Hercules slew it.
Hydra makes a rather fitting root word for Hydrilla
verticillata, a submersed, nonnative plant (from India) that first
appeared in Florida in the late 1950s, rapidly spreading throughout
much of the state.
Hydrilla 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 and various salinities and nutrient
conditions. Moreover, it can spread through fragmentation, sexual
reproduction (seeds), rootlike tubers and turions (bud-like
structures formed where leaves attach to the stems).
Hydrilla was introduced to Florida as an aquarium
plant. With few natural biocontrols, such as native insects or
diseases, the plant can rapidly occupy nearly the entire
water-column of shallow lakes. It can affect navigation, water
storage and water flow, which is needed to prevent flooding. It can
spread on boat motors or trailers even after it appears to be
thoroughly dried out, and it can survive the virtually dry soils of
dewatered lakes and rapidly take over when the lake refloods.
Chemical and other control efforts, including
biological and mechanical approaches, cost millions of state
The Florida Fish and Wildlife Conservation
Commission (FWC) is creating a long-term black bass management
plan, and one of the critical aspects to consider is that of
aquatic plant management and how to deal with exotic plants such as
hydrilla. In 2008, the legislature moved invasive plant management
from the Department of Environmental Protection to the FWC. An
intra-agency task force is actively working to develop new plans
and processes for managing hydrilla.
What makes invasive plant management so complicated
is that hydrilla can benefit recreational fisheries and waterfowl
populations and even help support endangered species such as the
snail kite. On the other hand, conservation philosophies and the
economics of attempting to manage it provide a compelling reason to
try to keep it out of new areas and control it before it harms
navigation, flood control, potable and irrigation water supplies,
recreation and the beauty of lakes.
A recent meeting dealing with management plans for
hydrilla on Lake Tohopekaliga, co-hosted by the FWC and the U.S.
Fish and Wildlife Service, highlighted some of the controversy.
"Lake Toho contains large amounts of hydrilla,
which can cause navigation problems and limit access to boaters,"
said Bill Caton, the FWC's Invasive Plant Management Section
leader. "This plant also provides an abundant food source and
habitat used by a nonnative variety of apple snail that lives in
the lake." In turn, the snail is eaten by snail kites, which are
among the most endangered birds in Florida, making Lake Toho one of
the few areas in the state where kites can find plenty of food.
Consequently, the FWC and the USFWS will adjust
when and where hydrilla is treated so enough snails will be
available when kites nest next spring. The Audubon Society and the
FWC want to protect snail kites. Other stakeholders, like the
Florida Freshwater Fisheries Coalition, want enough submersed
plants to provide good fish habitat but also open areas for anglers
to catch fish. If too much hydrilla is left untreated, plant
biomass could affect flood control.
Now that biologists have laid out these pros and
cons of hydrilla treatment in various situations, the FWC is
reviewing the first draft of the Black Bass Management Plan
In the meantime, does anyone know where we can find
another Hercules to take on our Hydra-illa issue? You can
contribute to the dialogue by completing a brief survey on aquatic
plant management at www.SurveyMonkey.com/s/bbmp_plants.