Fish kills common this time of year
Friday, July 23, 2010
Media contact: Carli Segelson, 727-896-8626
High temperatures and cloudy rainy days can spell
trouble for fish in Florida's rivers and lakes. These conditions
can cause fish kills, which are natural occurrences and typically
do not cause permanent damage to the ecosystem or to fish
Many factors can contribute to a fish kill. Some
fish kills are complex and involve a variety of factors that may
not be easily discernable. However, most common causes of kills in
brackish estuaries, freshwater lakes and man-made retention ponds
are well understood by scientists.
Fish kills are commonly caused by weather-related
factors. Sudden temperature fluctuations or extreme temperatures
can result in fish kills any time of the year. Hot weather during
the summer months can cause fish kills because warm water holds
less oxygen than cold water. In addition, a lack of rain during
hot-weather months lowers the water levels in the system, heating
the water and further depleting the oxygen in the system.
Fish kills also can occur during extended periods
with little sunshine. The process leading to these types of
die-offs begins with overcast skies and rainy weather. During
extended periods of overcast, rainy or cloudy weather, the
biological system uses the dissolved oxygen in the water faster
than it can produce it. Rain water can compound the situation
by causing vegetation, such as dead leaves and grass clippings, to
wash into the system and decompose. The decomposition process also
can remove oxygen from the water.
The good news is that most natural water bodies are
resilient to these types of fish kill events.
It is important for Florida Fish and Wildlife
Conservation Commission (FWC) scientists to keep track of the
location and extent of fish kills in natural lakes and estuaries to
see if there are serious problems developing in an ecosystem that
might require investigation or restorative measures.
Residents can report fish kills in natural water
bodies to the FWC at the FWC Fish Kill Hotline at 800-636-0511. It
is not necessary to report fish kills in man-made retention or
private ponds to the FWC.