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Florida’s drought affects fish,
wildlife too
June 18, 2007
Contact: Karen Parker (386) 758-0525
Florida is experiencing one of its driest years
on record.
The
U.S. Drought Monitor has the entire area rated from
"moderate drought" to "extreme" in South Florida. Water
restrictions are in place for many parts of the state. In South
Florida, a very dry 2006 (third driest on record for the state
as a whole) and a dry beginning to 2007 had Lake Okeechobee at a
record low of 8.89 feet on May 31. It should be at 13.23 feet.
It’s not just the state’s human residents who
are affected. The fish and wildlife are feeling the effects of
low water levels also.
According to Florida Fish and Wildlife
Conservation Commission (FWC) officials, there are both positive
and negative effects for the state’s wildlife during this time.
The cycle of floods and droughts that Florida
experiences is natural, normal and recurring. Florida’s
ecosystems are dependent on this cycle to maintain healthy fish
and wildlife populations. The long-term benefits of droughts and
floods often exceed the short-term negative effects.
“Short-term droughts probably are more
beneficial to freshwater fish and their habitat than they are
harmful,” said Fred Cross, regional freshwater fisheries
biologist in the FWC’s regional office in Panama City.
The drought exposes lake bottoms and dries up
the muck that has accumulated. Desirable vegetation expands into
deepwater portions of lakes and rivers, and seeds germinate on
exposed lake bottoms. However, during a drought, invasive and
exotic plants such as hydrilla can become more of a problem. It
also provides the opportunity to use prescribed burning to
reduce vegetation in the wetlands. This creates open water
habitat, which helps water quality and reduces the potential for
wildfires, according to Cross.
“Droughts can increase the effectiveness of
planned habitat enhancement projects,” said Dale Jones, section
leader for the FWC’s Division of Freshwater Fisheries
Management.
While water levels are low, boat ramps, docks,
seawalls and other structures can be repaired. Marine species
are able to go much farther upstream in some river systems,
providing additional fishing opportunities to freshwater
anglers.
Droughts can reduce the aquifer level, allowing
sink holes to form and drain lakes. Salinity increases in tidal
creeks may stress fish, and low water levels can trap fish,
resulting in fish kills from low dissolved oxygen, according to
biologists.
During these times of low water levels, boaters
need to exercise extreme caution to prevent striking an
underwater object or the bottom. At the same time, no matter how
shallow the water, there always is a drowning hazard. FWC
officials strongly encourage boaters always to wear their life
jackets while on the water.
There also may be access problems due to boat
ramps being out of water and steep drop-offs at power-loading
holes at end of boat ramps that are usable at current water
levels.
According to Allan Woodward, research
administrator at the FWC’s Gainesville Wildlife Research Lab,
“Droughts can be stressful on most aquatic wildlife, including
alligators.”
As water levels drop, alligators fare reasonably
well because of the temporary concentration of prey items (fish,
turtles and birds) into remaining water, although there may be
increased cannibalism.
“Under prolonged droughts, such as the one we
are now experiencing, alligators may be forced to move in search
of water. Traveling over dry land can cause increased mortality
from motor vehicles as well as dehydration. Smaller alligators
may fall prey to predators during these searches for water,”
Woodward said.
Movements across land usually will result in
more frequent interactions with humans, and alligators may get
trapped in areas from which they cannot readily escape. This
results in an increase in nuisance alligator complaints.
“We have found that there is no increase in the
number of attacks on humans during droughts. When moving over
dry land, alligators are awkward and out of their element. They
merely want to find water, which provides them with security and
food,” Woodward said.
Native reptiles and amphibians are adapted to
periodic droughts and occasional wildfires. Droughts and fires
can cause elevated mortality of reptiles and amphibians, but
most populations recover quickly when rainfall returns to normal
levels.
“In fact, some reptiles and amphibians depend on
fires to maintain their desired habitats,” Woodward said.
“Snakes normally are not as much of a problem during droughts as
during rapid water level increases after droughts.”
For marine species, there is good and bad news
during a drought.
For oysters, the increased salinity in bays and
estuaries means an increased risk of parasite infection,
according to Bill Arnold, research scientist at the FWC’s Fish
and Wildlife Research Institute in St. Petersburg.
“Clams are a high-salinity species, so drought
conditions generally are good for these bivalves. However, the
increased salinity also may support an increased abundance of
predators,” Arnold said.
Since most of the successful populations of bay
scallops occur offshore, they aren’t as strongly influenced by
freshwater inputs. Florida droughts usually occur in spring, and
the scallops spawn in fall or winter.
“By the time the drought sets in and has an
influence, the scallops are relatively large and more tolerant.
Scallops also are a high-salinity species, so it is the wet
rather than the dry years that appear to be more problematic,”
Arnold said.
For the upland species, there are also pros and
cons to the drought. According to Scott Johns, district
biologist from the FWC’s Olustee Field Office, hunters may
observe smaller and fewer yearling deer this fall as the drought
in North Florida occurred during the time when the fawns are
born.
“This made life more difficult on these fawns
and their mothers that need extra water in their diets while
nursing,” Johns said.
The tips and shoots of growing plants is a large
part of deer diets during the spring and summer.
“This is a favorite deer food, and without the
protein from these plants, fawn growth will be delayed and even
antler development in bucks could be stunted this year,” Johns
said. “Plant production is very limited during droughts,
especially those favored by wildlife such as blackberry,
palmetto berry, mushrooms and low bush blueberries. Plants shut
down new growth during periods of drought and conserve any water
available for survival.”
New growth is put off until favorable conditions
return. Oaks produce fewer acorns or may not produce acorns at
all during periods of drought.
Birds are generally unaffected by local drought
as they can move easily to find water. However, since this
drought has occurred during nesting time, many nests could have
been abandoned, and are at a greater risk of predation. Bird
nests are especially at risk during droughts mainly due to the
increased risk of wildfire. This would impact birds that nest on
the ground, such as turkey and quail, the most, according to
Johns.
Research has shown bobwhite quail reproduction
to be negatively affected by hot, dry periods. Although the
drought in North Florida has been very dry, it was relatively
cool, so quail reproduction may have not been severely impacted.
“Catastrophic events are also more likely during
drought years. Large-scale, fast moving wildfires can kill and
displace many species, especially those that are unable to move
quickly. Because birds are very
sensitive to air quality, they can be killed by smoke
inhalation, even when they are many miles from the fire,” he
said.
However, even fires can produce benefits.
Wildfires, which occur more frequently during drought periods,
can open up dense, tangled areas that have become overgrown and
useless to many species.
“For example, when wildfires burn the muck and
peat from dry cypress ponds and wetlands, this creates openings
and deepwater areas used by ducks, wading birds, and other
wetland species,” Johns said.
Gopher tortoises are somewhat adapted to life in
a dry environment. These animals are able to conserve water in
several ways.
“But the prolonged drought we have seen in North
Florida this spring could have significant impacts on the
hatchlings and juvenile tortoises,” Johns said.
Survival during a drought is easier on larger
animals than smaller ones. For example, white-tailed deer and
bears are able to cover large amounts of territory in search of
water.
“And as cruel as it may sound, the drought is
one of nature’s ways of eliminating the weaker, less vigorous
individuals of a species. Nature is continually eliminating such
animals from the population. The spread of disease and parasites
can decrease when these animals are gone,” Johns said.
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