The Florida Fish and Wildlife Conservation Commission stocked Lake-June-In-Winter with 2,500 grass carp Tuesday, Dec. 17. The fish are the most recent weapons to be deployed in the war on Illinois pondweed.
The sterile fish were introduced as a means of controlling new growth of pondweed. The first line in the offensive was aquatic herbicides that targeted the invasive weed. The two-fold plan is to use the herbicides to target and kill the pondweed, allowing the carp to maintain the project by eating new growth.
The project is being funded out of a trust set up for invasive plants that is paid into by gasoline taxes, commercial and public boat registrations and documentary stamps, according to FWC Regional Biologist Kelle Sullivan.
Sullivan and Steve Gornack carried bucket after bucket of fish to the water’s edge to release the weed-eating carp. Gornack is with the Aquatic Habitat Restoration Enhancement Section of FWC.
The triploid carp were brought in from a hatchery in Georgia instead of the anticipated Arkansas location due to winter storms making the original transport plans impossible. The carp are genetically altered to have three chromosomes instead of the normal two (diploid). This process renders the fish sterile. This important process is done to control the amount of fish present in the lake. Fish that are fertile could reproduce and cause too many plant-eating fish in the lake, leading to an imbalance of the fish- to-vegetation ratio. The result would be a decrease of oxygenating and habitat forming plants. “It’s not an exact science; there are many factors to consider,” explained Kelle.
Although grass carp have been implemented to battle other invasive plant species since the early 1990s, this is the first time in Florida that they have been used to control Illinois pondweed specifically.
“Typically grass carp are used for Hydrilla control,” Sullivan said. “They have plants they prefer and Hydrilla are at the top of that list.”
Despite the name, Illinois pondweed is native to Florida, it is sometimes called pepper weed as well. The weed has gotten a bad rap of late, but is actually an integral part of the lake’s eco system. It oxygenates the water and forms a habitat for marine life. Much of the pondweed was left untreated along the western side of Lake June-In-Winter, near the state park, because of its benefits.
Lake June is highly regarded as a recreational lake for fishing, boating and swimming. The weeds are wreaking havoc with boat propellers and have blocked access to many parts of the lake for these pursuits. Many homeowners on the lake have been frustrated by the attempts to control the weeds with herbicides alone.
Sandy Pelski was one of several lakefront homeowners present to watch the carp put into the lake. “I am hopeful; there are all kinds of pros and cons, I understand that,” she said. “Some of my friends that are fishermen aren’t happy about it.” Pelski said she has resorted to kayaking because the weeds were getting caught in her SeaDoo’s propulsion jets.
The grass carp are mainly herbivores and will only eat small insects if there is nothing else to eat. The fish introduced into Lake June are under a year old and approximately 12 inches long. The size of these carp will help to deter prey. This species can live from 15-20 years and can reach a weight of 45 pounds. The optimal age for weed control is 3 to 8 years; after that the carp’s metabolism slows down and they do not eat as much.
“Our hope is that, where we have treated, in very specific areas, is that the fish will prolong the treatment,” Sullivan said with optimism.