Fish Kills in Lakes

Sarasota County provides help to neighborhoods interested in keeping their ponds and waterways in good shape through the Neighborhood Environmental Stewardship Team (NEST).

• Fish kills in ponds and lakes are a common occurrence, especially in the summer.  The most common causes are related to weather, dissolved oxygen and natural systems that are out of balance. 
• Warm water holds less oxygen than cold water. 
• Rainy weather washes grass clippings and other vegetation into lakes where the decomposition process further reduces oxygen levels.
• Fertilizer washed into a pond will stimulate algae blooms that can also contribute to the oxygen decline.
• Overcast skies reduce the amount of light getting into the pond and reduce oxygen levels by reducing photosynthesis - the plant process that naturally adds oxygen to the water.
• This blend of contributing factors is why fish kills are so common in Florida.

In a week or less, fish kills typically resolve themselves naturally through the consumption of the fish by birds and wildlife and through decomposition of the fish carcasses. Low-oxygen fish kills are natural occurrences and typically do not cause permanent damage to the ecosystem or to fish populations. Some species, like tilapia, are more likely to suffocate than are other species.

Some ponds and lakes are less prone to fish kills. They are more natural and less influenced by fertilizer and runoff. They often have submerged vegetation and shoreline vegetation that keeps the pond in a healthier natural balance.

Report Fish Kill

To report a fish kill of concern call the Sarasota County Contact Center at 941-861-5000.
Fish kills may also be reported to the Florida Fish Kill Hotline at 1-800-636-0511 or online.
Learn more about fish kills at the Florida Fish and Wildlife Conservation Commission's Fish Kills webpage.