Fish Clean Lake Beds By Eating Weeds

Here's one way to clean weeds around your lake beds. According to the Orlando Sentinel, triploid grass carp fish have been stocked in one lake for the mission of eating weeds.

Our triploid grass carp must be happy. All the rain we had in December made lake levels rise, submerging stretches of grassy shoreline in shallow water. The carp, which eat only plant matter, have been munching on this newfound fodder ever since it entered an aquatic state.

When I go for a row, I often see the carp tugging at the stems and stalks of leafy weeds. The fish are so intent on feeding, they often don't realize I'm close until I'm practically on top of them. Then they startle, making big splashes in the process, as they swiftly swim away from my aluminum skiff.

Triploid grass carp have been eating wetland plants in our lake since May 2006. We purchased our stock during a period when the 12-acre pond was so clogged with floating weeds we couldn't swim without becoming entangled in stringy plants.

Although other methods of ridding the lake of weeds were suggested — removing them by hand (impractical), hiring a company to mechanically remove weeds (expensive) and using herbicides (environmentally questionable) — we opted for the carp. The idea of stocking the lake with an adequate number of plant-eating fish seemed like a practical, affordable and environmentally sound approach.

The grass carp, Ctenopharyngodon idella, are members of the freshwater fish family Cyprinidae, which also includes the minnow, goldfish and golden shiner. They are native to rivers in Siberia and China that flow into the Pacific, but now more than 90 countries around the world raise grass carp for aquatic weed control and aquaculture.

The fish's introduction to Florida's lakes began in the 1970s as a means to manage the extremely invasive weed hydrilla. Although grass carp were successful at controlling hydrilla, their voracious appetite for herbaceous plants raised concerns. If they reproduced in the wild, they might destroy valuable wetlands, swamps and waterfowl feeding grounds. Because of these concerns, scientists developed a means to genetically manipulate grass carp chromosomes so they have three sets rather than two, resulting in the production of sterile fish. Today, triploid grass carp is one of only two exotic fish in Florida — peacock bass is the other— that can be legally stocked in fresh water once a permit is issued.