Tilapia do reproduce and their offspring also assist in the control of aquatic plants. Tilapia are an excellent foodfish and resemble a two-pound bream when fully grown. In Texas, tilapia are stocked to give an extra forage base in trophy bass management. If properly acclimated, tilapia can survive and grow in water ranging from fresh to full strength ocean water. The stocking of grass carp has been restricted due to the possible ecological damage it could have on natural fish habitats. Various strains of common carp, especially Israeli carp, have been recommended for filamentous algae control.
These long-lived carp control filamentous algae by feeding in the pond bottom and breaking off the algae as it begins to grow. Their feeding habit in the pond bottom can have detrimental effects on ponds by causing muddy water. There is no predictive method to gauge whether ponds will become muddy or not. Since there are other biological and chemical control alternatives available, along with potential muddy pond problems; managers are advised to consider other control methods. Grass Carp: Sometimes referred to as white amur, grass carp were introduced to the United States in the s.
There was great debate among fisheries biologists about the ecological damage that a reproducing population of grass carp would have on natural fisheries habitats, so grass carp use has been restricted, particularly in natural public water bodies.
Mechanical Control – Plant Management in Florida Waters
Triploid Grass Carp: In the early s, biologists artificially produced a grass carp that is incapable of reproduction. Just after fertilization eggs are put under specific temperature or pressure regimens which cause fish to develop an extra set of chromosomes triploid. These fish are sterile, and there is no danger of these fish reproducing if they escape. Triploid grass carp became widely used as a method of aquatic weed control.
Water Use Situations
In , the South Carolina legislature legalized the stocking of triploid grass carp from certified dealers in private and public waters in South Carolina. Only government agencies may stock triploid grass carp in public waters, after thorough studies and public input have been received. Triploid grass carp can consume more than their own body weight of fresh vegetation in a single day and grow to more than 50 pounds. Grass carp feed largely on soft-stemmed submersed weeds such as hydrilla, pondweed, spikerush and naiads and are recommended primarily for control of these aquatic weeds.
Triploid grass carp will also control filamentous algae, when the fish are small.
As the fish grow their ability to control filamentous algae diminishes, so approximately six months of control should be expected from fish stocked at 10 inches long. Grass carp feed on duckweed and various harder stemmed aquatic vegetation types but generally do not provide satisfactory control of these species. Grass carp are selective feeders. When more than one noxious plant species is present; the carp will feed almost exclusively on the more preferred plant species before targeting the other available aquatic plant species. Ponds that are seriously impacted by noxious aquatic plant species high plant biomass should be managed to reduce the plant biomass either through the application of selected aquatic herbicides or by other methods draw- down, mechanical removal, etc.
Grass carp have some tolerance to brackish water, but should not be stocked in water with a salinity greater than 10 parts per thousand 10, parts per million. Stocking: Most submerged aquatic weeds can be controlled with a stocking rate of 20 to 25 triploid grass carp per acre of vegetation.
If only a portion of the pond has an aquatic weed problem, the stocking rate is based on the infected area only and not the entire pond. If there are no aquatic weed problems in a pond, a general recommendation is to stock triploid grass carp per acre.
- Water Use Situations.
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This will actively prevent the growth of aquatic weeds before problems start. It should be emphasized that even though grass carp will eat a particular plant, they may not control that plant unless fish are stocked in sufficient numbers and preferable plants are not available. Grass carp should be stocked in the spring for best results. Fish should be stocked at this time to allow them to aggressively feed on tender, young plant growth. Grass carp are sensitive to many water quality parameters. Hauling and stocking in the spring reduces stress due to adverse water quality conditions during summer and winter.
Grass carp are mainly herbivores but will consume insects, invertebrates, and other game fish food organisms.
There is no documentation that indicates grass carp are serious predators of other fish species. Grass carp will consume floating pelleted fish food. In ponds where supplemental feedings of bream or channel catfish are desired, you may want to consider other aquatic weed control options. If predators are present, larger triploid grass carp a minimum of inches in length should be stocked to reduce loss due to bass predation. The following is a list of potential grass carp predators that can seriously reduce or eliminate all grass carp:.
The impact of predators on young grass carp is one of the major reasons aquatic weed control is not successful when using grass carp as a weed control method. Grass carp prefer shallow water for feeding and can easily be seen swimming in small groups or individually at the surface of the pond.
Failure to observe these behaviors can indicate poor or no grass carp survival. Effective weed control should be evident 6 to 12 months after initial stocking. Grass carp are a riverine fish and will migrate from a pond if the opportunity is there. Any overflow deeper than three inches will encourage the loss of grass carp. However, herbicides should be applied as a last resort in suppression systems using a sound integrated pest management approach.
Application rates vary based on the system and environment, and efficacy of herbicides varies greatly depending on the specific herbicide and formulation and the specific weed to be treated.
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Effects of herbicides are strongly influenced by their toxic mode of action and their method of application Kaufman and Kaufman , Todd and Suter and either target a specific species or provide for a broad spectrum of control. Once the decision to use a pesticide has been reached, be it in an aquatic or terrestrial setting, it is important to be cognizant of local and state laws and be sure to always follow recommendations on the chemical labels.
The pesticide label is the best guide to using pesticides safely and effectively. The directions on the label are there to help an applicator achieve maximum benefits—pest control—with minimum risk to human health and the environment USEPA Recently enacted guidelines for aquatic pesticide use and permitting under the National Pollutant Discharge Elimination System in the Clean Water Act vary state to state and by EPA region, so it is always important to know the law and read the label. Remember, the recommendations from the Agricultural Chemical Manuals apply only to that state.
They may not be appropriate for conditions in other states and may not comply with laws and regulations outside of that state. We greatly appreciate the feedback provided from the meetings of the South Carolina Aquatic Plant Management Society and the Midsouth Aquatic Weed Management Society for management priority recommendations.
We also thank Dr.
John Madsen, Dr. Ryan Wersel, and Steve Hoyle who provided for insight on the most problematic weeds of the southeast component of this article. Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide.
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Aquatic Plant Control
Sign In. Advanced Search. Article Navigation. Close mobile search navigation Article Navigation. Volume 6. Article Contents. Management for Nuisance Aquatic Vegetation. References Cited. Oxford Academic. Google Scholar. Danesha Seth-Carley. Robert J. Cite Citation. Permissions Icon Permissions.