RECOMMENDED MANAGEMENT PRACTICES FOR MULTIPLE-BATCH CATFISH GROWOUT

POND SIZE

Economic studies suggested that the optimum pond size for catfish growout was 20 land acres (Foster and Waldrop 1972; Garrard et al. 1990). Another study suggested that farms with large ponds had greater variability of yield and that the optimal pond size decreased as the number of ponds likely to be off-flavor increased (Engle unpublished). However, optimal pond size increased with farm size. Larger farms, with space for a greater number of ponds, could take more advantage of the lower costs associated with building large ponds. However, there appears to be a trend in the industry towards building ponds smaller than 20 acres because they are easier to manage. Therefore, the recommended pond size for catfish growout is 10-15 acres (minimum 8 ac and maximum 20 ac).

WATER SOURCE

Groundwater is recommended because it is usually free of suspended solids, pollutants, fish diseases, and trash fish. Wells should supply enough water to fill the pond completely within 10 days to minimize vegetation problems (Wellborn 1988). Once the pond is filled, a 3/6 water management system should be used to minimize pumping costs (Pote et al. 1988). Ponds should be filled to 3 inches below the top of the overflow pipe. This allows for 3 inches of rainwater storage. If the water level falls to 6 inches below the overflow level the pond should be pumped up to the 3 inch level.

WATER QUALITY

Chloride concentrations should be maintained above at least 60 mg/l, but preferably above 100 mg/l to protect fish from nitrite toxicosis ("brown blood" disease). Elevated levels of nitrite are common in the fall, winter and spring, especially when water temperatures drop rapidly as cold fronts pass through (Tucker and Van der Ploeg 1993). Therefore, chloride concentrations should be checked prior to the fall and spring and after significant rainfalls.

Total alkalinity and hardness should be above 20 ppm but the desirable range is from 75 to 200 ppm CaCO3.

Unionized ammonia is toxic to fish, but the reported median lethal concentrations (LC50) for catfish vary widely, ranging from 0.17 to 3.13 mg/l NH3-N, because of differences in test pH, temperature, dissolved oxygen, CO2, Ca2+, and Na+ concentrations (Hargreaves and Kucuk 2001). However, brief daily exposure to concentrations of unionized ammonia above 0.91 mg/l reduces fish growth and results in poorer feed conversion ratios (Hargreaves and Kucuk 2001). However, because of the complex interaction between unionized and total ammonia nitrogen concentration, pH, water temperature, feeding rates, algae bloom, fish behavior and physiology, and economic factors, it is difficult to offer practical guidelines for safe ammonia exposure in catfish ponds. Unionized ammonia nitrogen concentrations should be estimated by measuring total ammonia nitrogen concentration, pH and temperature when fish go off feed, the bloom crashes, and after chemical treatments.

AERATION

Ponds should be equipped with electric paddle-wheel aerators at 2 hp/ac, with a minimum of 1 hp/ac. Oxygen fluctuations should be monitored daily and aeration initiated when the dissolved oxygen concentration is expected to drop below 4ppm. Aeration produces sufficient additional poundage of fish to more than compensate for the additional cost. Hence, aeration increases farm income. A morning oxygen reading (7-9 am) should also be taken throughout the winter to monitor oxygen conditions especially during periodic warm events.

STOCKING

In a traditional multiple-batch management strategy, fingerling stocking rates should be within the range of 6,000-6,500 head/ac, annually. Fingerlings should be stocked in the early spring of each year. Fingerlings should be tightly graded and the size distribution of the population should be assessed prior to loading onto the hauling truck. Minimum fingerling size should be 5 to 7 inch (35 to 91 lb/1,000) with absolutely no fish smaller than 5 inches because they result in lower survival and lower yield (Engle and Valderrama 2001).

A modular management strategy in which the fingerlings are raised to stocker size before to be transferred to growout ponds may also be recommended in some situations but did not constitute the focus of the present verification program.

FEEDING

Feeding should be done according to the feeding guidelines published in "A Practical Guide to Nutrition, Feeds, and Feeding of Catfish" (Robinson et al. 2001). The general feeding recommendations are:

• Feed Type: 28% or 32% protein floating 3/16" pellets

• Satiation Feeding: Fish will be fed as much as they will consume at each feeding without wasting feed.

• Summer Feeding: At temperatures between 22 and 30ºC (70-86ºF), fish should be fed every day, unless otherwise specified by your fish health specialist during ESC outbreaks for example. It is preferable to feed two times per day, late morning and early afternoon whenever possible. When water temperatures are above 30ºC (86ºF), ponds should be fed only once per day. Feeding every other day in the summer is not recommended even if using feed with higher protein content. Feeding every other day in the summer will limit fish growth especially of the understocked fingerlings and consequently reduce yields especially the following year (Engle personal communication).

• Spring/Fall Feeding: At temperatures between 12 and 21ºC (55-70ºF), fish should be fed every other day.

• Winter Feeding: At temperatures below 12ºC (55ºF), fish should be fed at least once per week, weather and levee conditions permitting.

HARVESTING

Harvesting should commence when records indicate that approximately 1,000-2,000 lb/ac of fish have reached an average weight of 1.5 lb, with a minimum of 10,000 lb ready for market. A month before the expected harvest date, fish should be checked for off flavor. If fish are off flavor, ponds may be treated with algicides or fish may be moved to another pond. Contact your aquaculture Extension specialist for more detailed recommendations.

FISH HEALTH MANAGEMENT

Farmers should immediately report and transport suspect fish to the diagnostic laboratory and follow the recommendations of the fish health specialist. In Arkansas, fish diagnostic services for fish farms and private ponds are provided by the Fish Disease Diagnostics Laboratories of the University of Arkansas at Pine Bluff. The best way to ship live samples of sick fish to the diagnostic lab is to put fish in a bucket or cooler of pond water and drive them directly to the lab. The best fish sample is sick fish that show obvious signs of disease or are alive but resting in the pond edge. Pond owners should walk around the pond and search for sick fish. Random fish can be collected by snagging, seining, or cast nets but these samples will only be useful in cases where a very high percentage of fish in a pond have an active form of the disease. Fish that are caught using baited hooks, or that are netted or snagged while fish feed, are not useful. Along with sick fish, a water sample from the affected pond should always be submitted to the diagnostic lab. This sample should consist of at least 250 ml (about 8 ounces) of water. It is important to rinse the jar several times in pond water before collecting the sample. Traces of soda, juice, detergents, or other chemicals contaminating sample bottles may lead to inaccurate water test results. The container should be kept cool and out of direct sunlight. For additional information on how to collect and ship a fish sample, contact the Fish Disease Diagnostics Laboratories of your area.

RECORD KEEPING

Farmers should maintain adequate records of the most important production parameters for each pond, such as:

• Stocking Records

• Harvest Records

• Daily Feeding

• Mortality Estimates

• Oxygen High/Low

• Flavor Checks

• Water Quality

• Medications or Treatments

Additionally, records of all operating expenses, fixed expenses, and revenues should be maintained and analyzed once a year to assess the financial status of the enterprise.

WORKER SAFETY

Farm workers should be given proper instructions on farm safety at least once a year. Check with your local county Extension office or Fish Disease Diagnostics Laboratory of your area on the availability of the "Fish Farming Safety Video", which is available in English and Spanish.

TREMATODE PREVENTION

Trematode infestations of white grubs, black grubs, yellow grubs (Clinostomum sp.) or eye flukes (Diplostomum sp.) are rarely more than a nuisance in catfish ponds. However, infestation of Bolbophorus sp. may cause high mortality rates and decrease production. Bolbophorus has a complex life cycle involving the American white pelican Pelecanus erythrorhynchos, the ram's horn snail Planorbella trivolvis, and fish (Overstreet et al. 2002). Considering that no bird depredation techniques have proved to be very practical and effective to date, the best method of controlling Bolbophorus infestation is to control snail populations. Triploid black carps Mylopharyngodon piceus, which feed on snails, are an effective biological control technique (Venable et al. 2000). Ponds in regions where the parasite has been reported should be stocked with triploid black carp at a rate of 5 to 20 fish/ac. Marginal pond treatments with copper sulfate have also been shown to be effective in reducing snail populations (Mitchell 2001) but should be used only if snail infestation is severe.

WEED PREVENTION

Grass carp Ctenopharyngodon idella should also be stocked at a rate of about 5 fish/ac to control aquatic vegetation.

GENETICS

Numerous studies suggest that USDA-103 catfish strain consume more feed and consequently exhibit a faster growth than other commercially available catfish fingerlings (Li et al. 1998; Silverstein et al. 1999; Jackson et al. 2001; Li et al. 2001). However, another study suggested that the Gold Kist strain performed better than the USDA-103 strain (Chatakondi and Yant 2003). Moreover, USDA-103 catfish do not seem to perform as well as other strains if they are not fed daily to satiation (Silverstein et al. 1999). The channel catfish x blue catfish hybrids also exhibit many desirable characteristics (Dunham et al. 1990, 1983; Wolters et al. 1996; Dunham and Argue 1998), but are more expensive and not as readily available. Acquire your fingerlings from a reputable farm source.