Health Management of Catfish from the Egg to Market

Catfish health is best managed by considering all aspects of production rather than applying treatments whenever an emergency arises. In order to manage for the best fish health possible, a whole farm plan must be made and followed by everyone on the farm.

Catfish Farm Design. This is an key point of planning toward fish health maintenance and disease prevention. When ponds are filled with water from sources other than groundwater of high quality, the health of the catfish grown in those ponds may be compromised. The water supply system should be designed in order to maintain pond water volume during dry periods of the year. Allowing ponds to remain partially full concentrates the fish and nutrients which results in water quality degradation. Facilities for aeration should be available and adequate for the pond sizes used. At least 2 horsepower and up to 4 horsepower of electric paddle wheel aerator per acre of water is needed to maintain dissolved oxygen levels in catfish ponds. Emergency aerators should also be available.

Marketing to Reduce Disease Probability. Marketing your catfish plays an important role in the control of disease frequency on a catfish farm. Catfish should be sold as soon as they reach the desired market size. Minimizing the time catfish are in your ponds makes good economic sense and reduces the time the catfish are exposed to possible disease pressures. Carrying over older fish and stocking fingerlings under them allows disease transfer. All fish that are captured during seining should be removed from the pond to avoid release of harvest stressed fish. Pond size should be designed so that it matches the volume of fish the market can accept.

Use Clean Seed Stock. Fingerling purchase must be controlled. This issue should be given special attention since starting with poor quality fingerlings will be problematic even with the best management thereafter. Fingerling management before purchase should be investigated since nutrition and stocking densities are important to the future health of the catfish. Deliveries of catfish fingerlings should be checked for signs of disease on arrival. Proper treatments should be administered or the fish returned to the source for treatment if disease is discovered. Stocking the fingerling at the right time is important. Hot weather and ESC seasons should be avoided. If the fingerlings are stocked at a time when they will not quickly respond to feeding, diseases may strike the fish as they become nutritionally weakened. Stocking densities of 5,000 to 10,000 catfish fingerlings per acre are used in the industry but the lower stocking densities are less likely to result in disease experiences.

Proper Nutrition. Utilize a completely fortified diet that is obtained from a reliable source. Some commercial diets without certain vitamins have been shown to produce adequate growth under commercial conditions, however, those diets may not be available in areas outside of the Mississippi Delta. Investigate the success of others who have used the diets before switching suppliers. Stick with success. Use the proper particle size for fish size. Inspect each lot of feed as it is delivered for mold, moisture, or fines. Then feed an adequate amount to keep your catfish growing at a rapid rate.

Observation by Trained Personnel. Monitoring catfish ponds for water quality and signs of fish distress is very important. A trained and experienced individual should conduct the monitoring program. Collection of dissolved oxygen values is important on a daily basis and for several times each day. Ammonia and nitrite should be checked weekly. Whenever fish are harvested, a sample should be examined for signs of disease so that the proper treatment can be planned. It is important to remember that monitoring should be a regular task of high priority, even when operations seem to be running smoothly.

Sanitation. Waste disposal is important to the spread of disease. When fish die, they should be picked up out of the pond as soon as possible and preferable within 12 hours. Catfish can be infected by consumption of the dead fish or as pathogens are shed from the carcasses. Burial, incineration, or composing has been utilized for disposal of fish. Local regulations should be investigated before disposing of catfish carcasses. Between crops of fish, the pond should be sanitized by applying chlorine, hydrated lime, or air drying. When ponds are partially harvested, older catfish will transfer any disease they may have to the new stock if an effort is not made to remove most of the old fish. Producers who use water from other ponds should treat and/or filter the water prior to pumping it into new ponds.

Records. Finally, records should be kept of your farm fish health program to allow you to identify areas of potential problems. Missing records usually mean that shortcuts were taken or that treatments were missed. Records will help with the economic evaluation of different treatments and help to decide when to treat a disease or to let it run its course. A good integrated fish health management plan will fit well with a quality assurance program. Both goals are similar in their aim to produce the best fish possible with sound economic principles.

 

Viral Diseases are a Danger to Grass Carp, Koi, Baitfish, and Goldfish

Spring Viremia of Carp Virus (SVCV) and Koi Carp Virus (KCV) are two serious problems that will affect the way carp and bait fish are shipped across state lines and internationally. SVCV has been confirmed only in North Carolina and Wisconsin in the U.S. But, this disease has swept across the carp industry in Europe. Common carp, koi carp, grass carp and goldfish were all attacked. It was also reported in the Wells catfish (the 'sheatfish') and in Hawaii in marine shrimp. It should be assumed that all cyprinid fish would be sensitive to SVCV. Most SVCV fish kills occur in the cool part of the year, when water is 60-70oF. Signs of the disease include swollen abdomen, red patches on the skin, and red spots on the swim bladder. These signs can be confused with bacterial or parasitic diseases.

Koi carp virus is another disease that may mimic bacterial diseases. Some of our pet stores have already seen the evidence of this disease. When it occurs, the holding system must be drained, dried and left dry for one month before disease-free carp can be returned. Prevention must include careful screening of any carp purchase. Your supplier should not have a history of these diseases. It would be best to buy from certified virus free farms, however there are only a handful of those. If you would like your farm certified virus free, the closest APHIS approved laboratory is in Pine Bluff, Arkansas. We can help you contact them if you are interested. In the meantime, be careful with carp purchases that involve interstate shipment.