Pesticide-contaminated water is suspected in the death of thousands of fish in canals west of Boca Raton earlier this year, state environmental regulators said.
In northern Palm Beach County, misuse of herbicides may have killed 200 fish in two ponds on a golf course last week, state environmental agencies said.
After investigating the death of 3,000 to 5,000 fish, including schad and tilapia, in two Lake Worth Drainage District canals west of Boca Raton in February, environmental regulators said they found fairly high levels of Thiodan — a chemical used on farm crops and ornamental plants — in the waterways.
The canals, called the E2E and E2W, run along the east and west sides of Florida’s Turnpike.
Thiodan — a brand name for endosulfan — is used to kill beetles and web worms on tomato plants. It is toxic to fish, birds, shrimp, crabs and other wildlife.
The pesticide is one clue the district is looking into while investigating a series of unexplained fish kills that have occurred over the past two years in the E2E and E2W canals, and in a few others west of Boca Raton.
Most have occurred during the same time of year, roughly January to March, said Mike Baker, aquatics director for the district, which oversees a 551-mile network of canals in the county.
“We’re seeing a pattern,” district director Bill Winters said.
He said the pesticide found in the February incident may have come from golf courses adjoining district canals but said it has not been traced to any.
“We’re really not sure what’s happening,” he said.
Near North Palm Beach, herbicide-tainted water is thought to have caused the death of 200 fish — including mullet, snook and sand perch — on June 10 in two estuarine ponds in Lost Tree Village, the state Department of Environmental Regulation said.
The fish were found after a herbicide company sprayed copper sulfate and kelated copper — two compounds used to kill aquatic plants and algae — in the golf course ponds, said Doug Strom, of the DER.
The findings will not be confirmed until laboratory tests of sediment and water samples taken from the two ponds are completed, he said.
Chemical toxins in drainage canals concern environmental regulators not just because they can kill fish and other aquatic creatures but because anglers eat fish they catch in the waterways, said Herb Zebuth, a DER water resources expert.
Farms and golf courses use a variety of chemicals and pesticides that can kill fish and other aquatic animals if sprayed near or in water. Sometimes the chemicals — even those properly applied — can be flushed into a canal or pond as run-off during a torrential rainstorm.
“We do occasionally come upon (a fish kill) that is herbicide or pesticide related, but it is extremely rare,” Strom said.
Most fish kills in the county occur naturally when the amount of dissolved oxygen in canals and ponds drops, environmental officials said. Changes in weather can cause that reduction: A string of cloudy days can hinder oxygen production in aquatic plants, or heavy rains can sweep decomposing, oxygen- consuming vegetation into the water.
Government agencies investigating fish kills do not automatically conduct water quality tests to look for toxins because they are expensive, Winters said. A single test can cost $1,200 or more, he said.
Prompted in part by the drainage district incidents, a group of state and local environmental agencies have banded together to devise a standard procedure for investigating future fish kills in the county, said Jackie Jordan, a biologist with the state Bureau of Aquatic Plant Management.
The protocol they hope to hammer out would help water districts and environmental regulators determine which fish kills can be dismissed as natural and which require more aggressive investigation, Jordan said.
