Since hydrilla was first identified in Spring Bayou in Avoyelles Parish, Louisiana Department of Wildlife and Fisheries biologists have continued to utilize all available control measures to fight the fast-growing aquatic weed. As part of an integrated plan including multiple control measures, Spring Bayou was stocked with grass carp in 2008 and again in 2011.
Hydrilla or Hydrilla verticillata, is a submerged, aquatic plant that grows rapidly in dense mats near the water’s surface. It is native to Asia and is classified as a federal noxious weed, making it illegal to transport across state lines without a federal permit.
A management plan for Spring Bayou is currently in place and will be updated annually with Department recommendations as well as the status of aquatic vegetation. LDWF staff has determined through routine sampling that the survival and growth of the stocked grass carp is positive. The fast growth of the fish indicates that consumption levels of hydrilla are currently high. The average size of the healthy young carp is now well over two feet long and up to ten pounds in weight. As the carp grow, their effects on hydrilla will become more obvious. If necessary, additional stockings will be considered.
Management recommendations for the waterbody include drawdowns and the use of herbicides for immediate control in high-use areas. Water fluctuations that mimic the natural cycle of the Spring Bayou back-water system are an effective vegetation control measure and can increase fisheries productivity. In order for a drawdown to be successful in Spring Bayou, some dredging will be necessary.
More than 21,000 triploid grass carp have been stocked in Spring Bayou. Triploid grass carp are fish with genetic modifications that make them sterile or unable to reproduce. The 2011 stocking was conducted out of concern that fish from the original stocking had been lost in Hurricane Gustav related fish kills.
After the hurricane, the Spring Bayou Restoration Team secured funding through private donations for 5,000 carp. The Department matched that number for a total of 10,000 carp in the 2011 stocking effort. Previous stockings were a cooperative effort of LDWF, Avoyelles Parish Police Jury and Spring Bayou Restoration Team. The efforts received strong support from Sen. Eric LaFleur and Rep. Robert Johnson.