Hungry fish nothing to carp about

Voracious eaters clean canals

March 7, 2008|By Sallie James Staff Writer

PLANTATION — They are mowing machines with fins, and on Thursday, the South Florida Water Management District dumped thousands of them into the weedy North New River Canal in a waterfall of shimmering scales to begin their work.

Known for their voracious appetites, approximately 20,000 triploid grass carp immediately began chewing their way through the tangle of plants that clog local waterways. The agency's nine-year-old canal-clearing program works well because the fish love to eat everything in their path, often growing up to 60 pounds, said Ellen Donlan, an environmental scientist for the District. The fish were released at two locations along the canal Thursday morning.

"I think it's a great solution. It's cost-effective, it's cheaper than chemical or mechanical control, and it lasts a longer time," Donlan said. The fish, about 10 inches long, cost the district $2.95 apiece, she said. The district spent about $150,000 on about 50,000 fish. The remaining 30,000 fish will be released in the Miami-Dade and Homestead areas, Donlan said.

The fish are called triploids because they have three sets of chromosomes instead of two, which makes them unable to reproduce. They are kept separate from natural areas adjoining the canals by barriers or structures, so they remained confined in waterways that are choked by nuisance plants, Donlan said.

"This is a grass carp's dream," Donlan said, pointing to the floating weeds in the North New River Canal near Interstate 595 in Plantation. "Some of the problems we have are with Asian plants and these fish are Asian. It's the natural food they like."

Chemical control of plants lasts only a short time and has to be reapplied, she said. Scooping the plants out mechanically is time-consuming, she said.

The fish were trucked in overnight from Lonoke, Ark., where they are farm-raised specifically for the purpose of canal cleaning.

Workers released the fish by attaching large plastic chutes to the huge fish tanks on the truck and then opening a valve.

The fish poured out in a gigantic spout of flopping tails, landing in a stream of splashes in the murky water of the canal where they swam off for a lifetime of feasting.

The district's main target is hydrilla, first introduced as an ornamental aquarium plant in the 1950s. Hydrilla has since invaded most of Florida's ponds, rivers and waterways, often growing in underwater stands or surface mats that are easily transferred by boat traffic.

"It's pretty much a bargain," said Christine Smith, a spokeswoman for the District. "They will eat just about anything and that is fine because we want to keep these canals clean for flood control. It keeps the water moving."


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