Management Of Recreational Fish Ponds In Alabama

---

Weed Control

Aquatic weed control is a common problem in farm ponds. Some aquatic vegetation might be good for the pond. Rooted aquatic vegetation does provide habitat for some small aquatic animals, which adds to the food chain. Vegetation also provides small fish with places to hide from larger predators. The problem with weeds is uncontrolled growth. If too many weeds become established in the pond, too many small fish survive (that is, over-populate), and removal of nutrients by the weeds reduces algae production (food). Also, predators become thin because they are not able to prey on the forage species.

Aquatic weeds can be controlled by manual, chemical, and biological means. Manual control of species like cattails is practical when they first start to colonize a pond. Woody vegetation along the dam also can be controlled manually.

Chemical control with herbicides is possible, but few herbicides are approved for aquatic use, and the type of aquatic vegetation must be accurately identified before it is treated. Herbicide applications can kill planktonic algae, leading to oxygen depletion. Oxygen depletions after herbicide treatment are particularly common in hot weather or if the pond is heavily infested with weeds, or in both conditions. Check with a fisheries biologist or the county Extension office for plant identification and current herbicide recommendations. When using chemical pesticides, protect yourself and others by strictly following all label directions.

(Photo left) Grass carp grow rapidly and will control most underwater weeds if stocked at recommended rates.

The simplest and most economic long-term aquatic weed control method is to stock grass carp. The grass carp, or white amur, is an Asian carp brought to this country for aquatic weed control. Grass carp consume vegetation almost exclusively after they reach 10 inches in length. They will not reproduce in the pond, will not muddy the pond like common carp, will not disturb the nests of other fish, and they will consume 30 to 40 percent of their body weight in weeds every day during warm weather.

Grass carp are attracted to running water and will leave the pond over the emergency spillway during heavy rains. Prevent escape by building a correctly designed barrier across the spillway. A list of where to purchase grass carp and information on how to build an escapement barrier can be obtained from your county Extension office.

The number of grass carp that should be stocked depends on the type of weed, condition of the pond, and magnitude of the weed problem. Table 6 gives recommended stocking rates. If stocking grass carp into a pond with mature bass, stock an 8-inch or longer (10- to 12-inch) fish. Grass carp are less effective at controlling weeds after they reach 20 to 30 pounds in size (usually 5 to 7 years after stocking). As vegetation starts to reappear, restock the pond with new grass carp fingerlings. Remove the large grass carp by bow-fishing or spearing. Grass carp are excellent table fare.

Table 6. Recommended Stocking Rates For Grass Carp.

Weed Evaluation	Number of Fish to Stock per acre
New pond or very slight weed problem	5
Moderate weed problem (10 to 20 percent coverage)	10 to 15
Severe weed problem	15 to 20 or more

In the case of a severe weed problem it may be practical to treat the pond with a herbicide first and then to stock 10 to 15 grass carp per acre to maintain weed control. Contact your county Extension office for information on chemical control of aquatic weeds.

BACK | MAIN | NEXT