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Chemical Control Can Protect Young Catfish
MISSISSIPPI STATE -- Bacterial and fungal problems that can kill millions of catfish eggs a year can be kept under control with simple chemical baths, a practice that saves the industry thousands of dollars a year.
Mississippi State University's Extension Service is showing catfish hatcheries that some devastating disease problems can be solved by flushing egg masses twice daily with iodine or other antibacterial/antifungal compounds.
Mississippi's catfish industry had a farm-gate value of $307 million in 1998. The state has numerous hatcheries of various sizes producing a total of about 2 billion catfish young, or fry, each year. While some hatcheries produce as many as 100 million fry a year, most yield 30 million to 50 million annually.
Jim Steeby, area Extension agent for aquaculture at Mississippi State's National Warmwater Aquaculture Center, said fry sell for $5,000 to $6,000 per million. Hatcheries can easily lose a few million fry annually to bacteria and fungus. Cutting losses by 2 million at each location could save a hatchery $10,000 or more a year, or the statewide industry at least $500,000.
Bacterial problems peak when hatcheries operate at near maximum capacity. Crowded hatch baskets prevented water from circulating as it should through the egg masses, keeping them healthy.
"Bacteria can grow on the shell of the catfish egg and disintegrate the eggshell so the embryo has no protection. We call it premature hatch," Steeby said. "Typically these embryos that are not fully developed fall through the hatching baskets and die."
Steeby encourages producers to inspect egg masses by look and feel twice daily for bacterial problems and once a day for fungal problems.
"If you're having a bacteria problem, the eggs will have a slimy or slippery feel," Steeby said. "A healthy egg mass has a rubbery, latex feel like a wet rubber glove. Egg masses with a white cotton or dirty look typically have a fungal problem."
Many bacterial problems can be prevented or treated with a twice daily iodine wash. This wash is similar to a surgical scrub, but without soap, and is applied to the hatching water. Fungal problems can be treated with either an iodine or salt wash. The cost of these treatments are very low, but effective and necessary.
"We typically hatch about 80 percent of the eggs we bring in," Steeby said. "If our problems are not controlled or we don't pay attention, that could drop easily to 50 percent."
Louie Thompson, owner of Thompson Fisheries in Thornton, hatches about 50 million catfish a year. Problems can develop in hours, but he said a regular schedule of treatments can keep producers ahead of the disease.
"You can check a tank and it seem healthy, and then you check it a couple hours later and it can already be a problem," Thompson said. "If you really stay on top of it, you can almost eliminate losses from bacteria and fungus."
This year Thompson's hatchery had a particularly heavy hatch and faced more problems than usual with bacteria and fungus. In previous years, he has relied almost exclusively on regular bath treatments to keep fungus in control. This year's overcrowding increased bacteria problems, prompting him to start iodine treatments.
"We treat the tanks with iodine twice a day until an eye develops in the eggs," Thompson said. "Once the problem shows up, it's hard to get back under control and you're going to end up losing eggs."
The optimum temperatures this year for catfish breeding were also ideal for bacterial growth. Extension agents helped producers survive the disease stage through application of this knowledge about treatments.