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U.S. Department of Health and Human Services

Animal & Veterinary

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FDA Veterinarian Newsletter September/October 2001 Volume XVI, No V

In May, members of the Aquaculture (AQ) Drugs Team of CVM's Division of Therapeutic Drugs for Food Animals took a minisabbatical to Mississippi and Arkansas to learn about the farm-raised catfish industry. Members of the AQ Drugs Team include Joan Gotthardt, D.V.M.—Team Leader, Mr. Ben Puyot-Consumer Safety Officer, and Don Prater, D.V.M. and Susan Storey, D.V.M.—Veterinary Medical Officers. Mr. Hugh Warren, Executive Vice President of the Catfish Farmers of America (CFA) organized the tour. Mr. Warren is a long-time resident of the Greenwood, Mississippi area and has been in his current position for about 12 years. Rosalie "Roz" Schnick, the National Aquaculture NADA Coordinator since 1995, accompanied the AQ team on the tour.

The team learned a lot of basic information about the catfish industry as well as more specific information about the catfish industry in the Mississippi Delta. Catfish are the number one farmed finfish in America.

More catfish are produced in the U.S. annually than all other farmed fish combined. Mississippi, Arkansas, Alabama, and Louisiana produce 95% of the U.S. farm raised catfish with ponds covering 140,000 acres of these 4 states. The single largest catfish farm has 8,000 acres of ponds. The farm-raised catfish industry contributes $2 billion to the Mississippi economy annually.

Catfish in the Mississippi Delta are raised in levee-type ponds in fresh water from underground wells. The clay-based soil of the region provides an excellent substrate to build the levees and to retain the water in the ponds. The ponds average 10 to 20-acres in size with most ponds being closer to 20 acres. The 20-acre size is a compromise between ease of management and the cost of construction. One company farm the team visited had recently drained several ponds after more than 10 years in production in order to rebuild the levee walls. A company representative indicated that most of the farm's 20-acre ponds would eventually be divided into 10-acre ponds. The representative stated that the 10-acre ponds would be easier to feed and harvest and the wind would cause less wave action and therefore less erosion of the levees. The estimated cost of building the levee to divide a pond is $20,000.

Most ponds are rectangular, but can be other shapes depending on topography and property lines. Pond depth averages 4 to 6 feet with a shallow end and a deep end to assist drainage. Ponds are seldom completely drained. Ponds are drained by gravity through a pipe that empties into a ditch. The drains and ditches are designed to maintain the water level at no higher than 1-1/2 feet below the top of the levee. The drainpipe must also keep the catfish in the pond and other fish species out. Ponds are harvested year round and the average 20-acre pond produces 4,200 pounds of catfish yearly.

The first day of the tour included an aerial overview of catfish ponds in the Mississippi Delta. Many areas have ponds as far as the eye can see. What is really noticeable from the air is not only the varied shape and size of the ponds, but also the varied color of the ponds. The ponds can be blue, green, brown, or any combination of these colors. Agitated pond sediments and algae are thought to be the main determinants of water color. Often ponds that are managed identically look very different.

Following the aerial overview, the team visited the USDA-Agricultural Research Service's Harry K. Dupree _ Stuttgart National Aquaculture Research Center (SNARC) in Stuttgart, Arkansas. Donald Freeman, Ph.D., the director of the Center, outlined the research initiatives of SNARC. Mr. Billy Griffin, microbiologist, led a tour of the Center. SNARC was originally established in 1958 and dedicated in 1962. Its purpose was to develop a program of research and experiments to solve problems related to the production and harvest of warm-water fish. The Center was transferred to the USDA from the Department of the Interior in 1996. In 1992 an 18,000 square foot building was completed with 60% of the building devoted to research labs. Many of the laboratories have recently been equipped with state-of-the-art equipment needed for the research performed at SNARC. The Center also has a 3,700 square foot building with 72 aquaria and numerous troughs and tanks. An 8,000 square foot covered "tank farm" contains 120 four-foot diameter fiberglass fish tanks as well as a small hatchery area. Outside are seventy-two tenth and quarter-acre ponds, nine 1.0-acre ponds, two 1.5-acre earthen raceways, a 3-acre holding pond and a 27-acre reservoir. Three wells supply the water for the tanks and ponds, at a rate of up to 2,500 gallons per minute. The Center has a water treatment plant to handle all discharges and has equipment to manufacture pelleted fish feed needed for research projects.

Research at SNARC is primarily on warm-water fish species other than catfish including striped bass, tilapia, carp, eels, ornamental species, and baitfish. Studies have been done evaluating the safety and efficacy of aquaculture therapeutics and determining therapeutic drug residues in the edible tissues of fish. SNARC is also working to develop practical diets for hybrid striped bass and other fish species. During nutrition studies researchers measure fillet yield, feed conversion, and body composition. Recent research has been done to determine the physical and chemical factors that maximize production of zooplankton, an important source of oxygen in the pond and food for some stages of development of some species of fish. Researchers are attempting to develop management practices for year-round pond production of zooplankton.

Another area of research at SNARC, as well as a large concern for the catfish industry in MS, is bird depredation. Pond culture systems provide ideal habitats for many migratory birds. Doublecrested cormorants, American white pelicans, ducks, herons, and egrets create substantial loss from the ponds. To disperse the birds many types of non-lethal harassment have been tried, but with limited success. Since 1972, AL, AR, LA, and MS have seen increased recoveries of cormorants banded in breeding areas as young birds. SNARC purchased satellite transmitters that researchers from the National Wildlife Research Center (MS Research Station), in cooperation with USDA's Wildlife Services programs in LA, AR, MS, and AL, placed on fifty cormorants captured from November 1999 to March 2000 and from October 2000 to March 2001. The transmitters allow researchers to determine where individual birds move during the winter, where the bird breeds in the spring, and the bird's migration path. Data received last winter, the first year of the study, indicate that double-crested cormorants wintering near southeastern catfish farms have a broad breeding distribution. The cormorants breed anywhere from southern Manitoba, Canada, to northern New York State. The information collected will aid the determination of how best to manage a cormorant population in which individual birds can live up to twenty years producing two young per year.

A relatively recent problem in the Delta has been the rapid spread of the digenetic trematode, Bolbophorus confusus. Mr. Andrew Mitchell, a researcher at SNARC, explained that pelicans carry the trematode. The ram's horn snail (Planorbella trivolvus), a normal inhabitant of the ponds, serves as the intermediate host for the trematode which then infects the catfish. The trematode kills numerous fingerlings every year, slows the growth of surviving catfish, and makes infected fish unmarketable because the parasite matures in the muscle of the fish. Mr. Mitchell investigated copper sulfate as a safe and effective method to reduce the number of snails in the ponds. Copper sulfate has been granted EPA registration to control snails around the perimeter of ponds. Mr. Mitchell is also considering studies with therapeutics that may be administered to the catfish to reduce the number of trematodes in the fish.

After returning to Greenwood, MS, the next stop on the tour was Thompson Fisheries. Thompson's is a catfish hatchery in Thornton, MS. Mr. Bobby Thompson started the hatchery in 1959. Today Mr. Thompson's son, Louie Thompson, runs the business. The hatchery produces 5-6 billion fry (young fish) annually. The catfish spawn in ponds from mid-April to July. Catfish lay their eggs either in or under something. At Thompson's, the fish are provided with surplus ammunition cans. The cans are checked by hand for eggs every 3 days. The egg masses are placed in baskets in special tanks in which the water is continuously circulated around the eggs. The egg masses must be handled carefully to prevent dead eggs, which are susceptible to bacterial and fungal infections. Healthy eggs hatch in about 5 days. Once hatched, fry are transferred to progressively larger tanks. Wells supply the fishery's water. A 1,700-foot deep artesian well produces 90 °F water and a second well produces cooler water that is added to provide the correct temperature water for the tanks. The fry are maintained and fed in the tanks for approximately 6 weeks. When the fry are swimming and feeding well, they are transferred to ponds. Mr. Louie Thompson estimated that 90% of the eggs hatch, however a substantial number of fry are lost in the first two days after transfer to the ponds. The hatchery sells both fry and fingerlings (3-4 inch fish) to producers. Young catfish are transported in specially designed trailers with large tanks supplied with oxygen during transport. One trailer can transport up to 1,000,000 fish at one time. A newer trailer is large enough to transport up to 2,000,000 fish at one time. Once delivered, the fish are stocked in ponds and reach a market size of approximately 1-1/2 pounds in 18 months.

The second day of the tour started at SouthFresh FarmsTM a producer of farm-raised, grain-fed catfish in the Mississippi Delta since 1976. In 1980, SouthFresh constructed 640 acres of ponds in Morgan City, MS. In 1988, a processing plant was built for the farm. At that time, the plant was processing 50,000 pounds of catfish weekly. The farm was expanded to 1,615 acres of ponds in 1990 and in 1995 the capacity of the processing plant was increased to 500,000 pounds per week. In 1999 SouthFresh FarmsTM merged with Alabama Farmers Co. providing a 780-acre fingerling farm and a feed mill. With this merger, SouthFresh FarmsTM became a vertically integrated company, owning and managing the catfish from source to finished product. A new state-of-the-art processing plant, capable of process ing 500,000 pounds of catfish weekly, was just completed in Alabama.

Mr. Julian Allen, chairman of SouthFresh FarmsTM, led a tour of one of the SouthFresh farms. As well as the ponds, the farm also has an on-site hatchery. A small office in the hatchery building houses the control center of the farm. Information about each individual pond is maintained on a computer in that office. The amount of feed for each pond is calculated and transmitted directly to a computer system in the truck that delivers feed to the pond. The number and size of the catfish as well as the pond temperature determine the amount of feed delivered to the pond. After sunset and throughout the night, workers measure oxygen levels in the ponds every 1-2 hours. The oxygen levels are transmitted to the computer. The farm manager monitors the oxygen levels to decide when to turn on pond aerators and how many aerators are needed in each pond. Most catfish ponds have one or two stationary aerators. Stationary aerators are electric, float on pontoons and have a large number of paddles attached to a central shaft. When on, the paddles agitate the water, adding oxygen to the water. Most farms also have aerators operated by tractors. These aerators can be moved from pond to pond as needed.

Mr. Rivers Myers III, president of SouthFresh FarmsTM, conducted the tour of the processing plant in Baird, MS. Prior to harvesting, farmers bring samples of their catfish to the plant. The fish are taste tested by professional tasters to prevent "off-flavor" fish from reaching the consumer. Catfish fillets should appear an opaque white when raw and have a mild, delicate taste when cooked. The catfish are individually graded for size on entering the plant. The processing machines are all automated and set to handle certain size fish. Separate machines dehead and eviscerate the fish, skin and fillet the fish. Fish that are too large must be hand filleted. With two operators a fillet machine can process 24 fish each minute. The fillets are quickly frozen within 30 minutes to retain the original quality of the fish. The freezing takes place in a spiral freezer with a variable speed belt regulated so that the fillets are in the freezer the correct amount of time.

The team next visited Harvest Select Farm, a broodfish and research farm in Inverness, MS. Harvest Select works to improve the genetics of catfish through research and natural selection and has 492 acres of ponds. The company helped develop a new strain of catfish, NWAC-103. The first shipment of this catfish strain was in February 2001. Nagaraj G. Chatakondi, Ph.D., a research coordinator in the aquaculture division, explained his current work with a blue catfish-channel catfish hybrid. The hybrid catfish are more aggressive eaters, grow faster, and are more resistant to certain bacterial infections. Dr. Chatakondi's main research concerns improving spawning and subsequent hatching of eggs.

While at Harvest Select the AQ team saw a pond being harvested. The pond had already been seined and the fish confined in the "sock". A seine is a weighted net that stretches across the pond and from the surface to the bottom of the pond. The nets have different size holes to keep the desired sized fish in while letting smaller fish swim out. The ends of the seine are attached to the "sock", a circular net, in one corner of the pond. The fish are swum into the "sock" and left for at least two hours to give the smaller fish time to swim out. Fish are transferred from the sock to the transport truck in a large basket operated by a crane and are weighed in the basket. The transport trucks have multiple, oxygenated tanks, so that the fish are delivered alive.

The last day of the tour was spent at the Thad Cochran National Warmwater Aquaculture Center (NWAC) and the Delta Western Feed Mill. The NWAC is located at the Delta Research and Extension Center in Stoneville, MS. The NWAC, USDA Agricultural Research Service, Mississippi Agricultural and Forestry Experiment Station, Mississippi State University Extension Service and MSU College of Veterinary Medicine serve as the base of the U.S. catfish research and extension service. The primary mission of NWAC is to combine research, extension and diagnostic services to provide solutions to the most pressing problems of the aquaculture industry. Patricia Gaunt, D.V.M., Ph.D., assistant professor MSU-CVM, led the tour of NWAC. NWAC has 243 earthen ponds from 0.1 to 9 acres totaling 180 water acres. The team met David Wise, Ph.D. and saw some of the research projects he had set up in and around the ponds. Dr. Wise investigates catfish diseases and is currently developing infection models for some of these diseases. The team also toured the fish diagnostic labs. The lab, run by Lester Khoo, V.M.D., Ph.D., provides diagnostic support for the research projects and the catfish farmers in Mississippi. Dr. Khoo demonstrated necropsy methods on catfish brought in by local farmers. The catfish were suspected to have enteric septicemia of catfish (ESC) caused by Edwardsiella ictaluri. ESC is the most devastating bacterial infection in catfish. Infections generally occur in the spring and fall of the year. The infection can quickly kill all the fish in a pond. Mr. Tim Santuci, Medical Technologist, demonstrated culture and identification techniques for E. ictaluri, which only grows at 25-30 °C.

Mr. Dwayne Holifield, B.S., manager of the research farm led the tour of the Delta Western Feed Mill in Indianola, MS. Delta Western Research Center has several tenth-acre ponds. The ponds are used for research projects involving nutrition and field trials of therapeutic products. The research center also has a second mill used to produce smaller lots of experimental catfish feeds. The research unit works extensively with NWAC. The main mill produces about 230,000 tons of catfish feed annually representing thirty percent of the 825,000 tons of catfish sold annually. Railroad lines bring grain products used in the feed directly to the mill. Three large warehouses store ground corn, wheat middlings and soybean meal that are pumped directly into the mill as needed. The mill has doubled its finished-feed storage capacity over the last two years to a capacity of 5,000 tons. The mill operates two 8 - 10 hour shifts depending on the time of year. The storage area is filled completely by the end of the second shift and emptied by mid-morning the next day. The feed is delivered to farms in large tanker type trucks. Each truck has a capacity of 20 tons and can be completely filled in 2 1/2 minutes.

The mill produces a floating pellet type feed. Farm-raised catfish feed at the top of the ponds. These catfish are not the bottom feeders catfish are traditionally thought to be. Corn, wheat mids, and soybean meal are cooked, under pressure, at 190-300°F and steam is added to produce mash. The mash is forced through a die with holes sized to produce the proper pellet size. A sudden decrease in pressure after extrusion causes vaporization of part of the water and the pellet expands. The pellets are then placed in driers with the capacity to hold up to 20 tons of feed to produce the final floating pellet product.

The aquaculture team did not spend all their time looking at and learning about catfish. They also sampled quite a bit of catfish. SNARC and SouthFresh FarmsTM both hosted lunches featuring traditional southern fried catfish and all the requisite side dishes. The team also tried blackened catfish and lemon pepper catfish at the Crystal Grill, a well-known restaurant in Greenwood, MS. Dr. Gaunt made sure the team had lunch at the famous Crown Restaurant. The Catfish Allison is required eating for those who have never been to the Crown. The acquaculture team did not come home hungry.