Life on a Fish Farm: Food Safety a Priority : Part 2

by Food and Drug Administration (FDA)

(Page 2 of 3)

Raising Catfish

Catfish farming makes up 50 percent of the U.S. aquaculture industry and typifies aquaculture in action.

The life of a farm-raised catfish begins with the mating of genetically bred broodstock. Broodstock are sexually mature fish used solely for reproduction. They are so important that some farmers specialize in their production.

Typically, once the eggs are laid and fertilized, they are placed in controlled hatching tanks with oxygenated water of suitable temperature and quality. The eggs hatch in seven to eight days, and 18 days after hatching the young catfish — "fry," as they are called — are strong enough to be transferred to outdoor ponds to mature.

The pond size may vary from 5 to 20 acres, is 4 to 5 feet deep, and is usually fed by a good supply of well water. Catfish fry, which are less than 1 inch long at this point, are stocked at densities ranging from 70,000 per acre to upwards of 200,000 per acre, as recommended by hatchery biologists.

Once fish enter the pond, their growth and survival will wholly depend upon the quality of that environment. Everything the fish comes into contact with has the potential of becoming a part of the edible flesh of that organism and can affect its life. If the water or food contains contaminants, they may end up in the fish. If improper drugs are used to treat a disease, residues of those drugs may also become a part of the fish. If too many aquatic plants are present, they will compete with the fish for oxygen. Sound management is essential to keep the fish growing.

So, from the time of stocking to the time of harvest, the farmer is busy controlling the aquaculture system.

First, every attention is given to the quality of the commercially prepared dry pellet diet. It must be high in protein (30 to 40 percent, depending upon the stage of growth), made of soybeans, corn, wheat, and fishmeal, and contain a balance of essential vitamins and minerals in accordance with recommendations by the National Research Council and fish nutritionists.

Under FDA requirements, the mill that produces the feed guarantees that ingredients are present at the levels declared on the feed label and that feeds containing medications meet drug level specifications.

Prior to pelleting, the mill also analyzes each ingredient to guarantee the absence of toxicants or contaminants. Feeds contaminated with aflatoxins — toxins that occur in moldy feed ingredients — can cause fish deformities and even kill the fish. FDA inspectors routinely examine the mills' feed test results and evaluate their good manufacturing practices.

A balanced diet of floating pellets is mechanically scattered on the fish pond's surface once or twice daily. Fish gourmets credit the pellet for the catfish's distinctive flavor, which they say they would recognize blindfolded. Others say the taste comes from the sweet well water in which the catfish grow. This, too, is managed by the farmer.

Even before the fish go into the pond, water quality and location are concerns. The farmers make sure the pond's soil is free of pesticides and not contaminated. Then they secure an abundant source of clean water. Most catfish farmers use well water because of its desirable chemical makeup and lack of contaminants.

The water quality must be constantly checked for optimum growth requirements: proper temperature, the right amount of oxygen, the appropriate water chemistry, and just the right balance of aquatic plants and weeds.

To operate, the farmer must meet state and local requirements on water usage and discharge, as well as the appropriate EPA water permits. Only FDA-approved drugs may be used, with strict adherence to directions for use — particularly directions that tell when the drug must be stopped or "withdrawn" to prevent residues in the fish at the time of harvest.

FDA is alert to the potential misuse of drugs and chemicals, including the use of unapproved drugs or chemicals. The agency has approved only five chemicals — including three antibiotics — for use in combating diseases caused by bacteria in the aquaculture environment. The fish-farming industry maintains that this is not enough, especially with resistant strains of bacteria developing to approved antibiotics.

FDA supports research to obtain data on the safe use of certain drugs and is encouraging drug manufacturers to develop additional therapies for approval. At the same time, they have developed an enforcement strategy directed towards those who violate the law by selling or using drugs unapproved for use in food fish.

To learn the extent of drug use in aquaculture, FDA's Center for Veterinary Medicine, working with field investigators, recently completed a survey of catfish, crayfish, and trout producers. The center and the Office of Seafood are now developing additional analytical methods to test fisheries' products for drug residues. The center is focusing on illegal residues of drugs from off-label use: drugs approved in species other than fish that might be used in fish. The Office of Seafood is focusing on drug residues that may be in imported seafood and has increased sampling of aquaculture products — both domestic and imported — for pesticides and industrial chemicals.

Under the best conditions, 18 to 24 months after hatching, the catfish reach a market weight size of 1 ¼ to 1 ½ pounds. They are transferred from the pond to water-laden, oxygen-treated tank trucks for live shipment to the processing plant.

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.