Cold weather may lead to fish kills
Thursday, December 09, 2010
Media contact: Carli Segelson, 727-896-8626
As temperatures drop in Florida, the number of
cold-related fish kills is likely to increase. Chilly winter
temperatures can lead to fish die-offs in Florida's marine
habitats, rivers and lakes.
The good news is that these events are natural
occurrences and typically do not cause permanent damage to the
ecosystem or to fish populations. In some cases they are even
beneficial, in that they help limit the spread of invasive, exotic
Fish kills are often caused by sudden temperature
fluctuations or by extended periods of extreme temperatures. Such
kills can occur any time of the year in Florida, but they are most
common in winter, when air temperatures drop. Although water stays
relatively warm for awhile after the air cools, extended cold snaps
can cause water temperatures in inland water bodies and estuaries
to drop. The cold may kill fish outright by cold stress or weaken
them so that they are more susceptible to disease. Another
phenomenon, called lake-turnover, may occur when suddenly cooled
surface water sinks and mixes with deeper, oxygen-poor water. This
can cause fish to suffocate, often leading them to gulp at the
surface before they die.
Warm-water species, including popular game fish
like snook, are particularly vulnerable to cold temperatures.
Exotic species such as butterfly peacock bass, tilapia, and
sucker-mouth catfish are also especially susceptible to cold
Fish affected by the cold may appear lethargic and
may be seen at the surface where the water may be warmer from the
sun. All recreational regulations still apply to fish impacted by
the cold temperatures, even if they appear to be dead or dying.
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 problems developing in an ecosystem that might
require investigation or restorative measures. Although it is not
necessary to report fish kills in private ponds, FWC scientists can
assist the public by providing information about cold-weather fish
kills in these water bodies.