MISSISSIPPI STATE -- Living in the water doesn't spare Mississippi's catfish from the effects of summer heat as recent daytime pond temperatures have reached the high 90s.

Jim Steeby, area Extension aquaculture agent with Mississippi State University's National Warmwater Aquaculture Center, said water temperatures in the Delta where he is located have stayed at 95 degrees in the afternoon since the last week of July. While catfish thrive in warm weather, this level is too hot.

"Aeration concerns are critical as fish go into stress in 5 to 10 minutes in this heat without oxygen. You can lose a whole pond," Steeby said. "Our biggest problem is if we have any kind of glitch with our aeration equipment, there's almost no time to get the equipment running again before the fish are stressed."

Plants in the water produce oxygen during the day through photosynthesis. While this supplies the catfish's oxygen needs during the day, the excess oxygen in the water is used up rapidly at night. Catfish breathe faster in the heat, requiring more oxygen than usual. They suffocate if oxygen levels drop too low.

"Growers typically start aerating about 10 p.m. or midnight and shut the equipment off at daybreak during the summer," Steeby said. "Lately, they've had to run the aerators from sundown to sunup. If the sky is clear when the sun comes up, they can turn them off around 8 a.m., but if it's cloudy, they have to leave the aerators running until about 10 a.m. to supply enough oxygen."

Jon Cooper is general manager of the nation's largest catfish farm, Tackett Fish Farm in Schlater. He said he's had more oxygen trouble than usual this summer and feeding is slow.

"The heat has cut our feed back some," Cooper said. "Three weeks ago we were feeding more than we are this week, which is below where it should be."

Cooper said demand for catfish is outstripping supply mainly because growers harvested smaller fish than usual last spring. Processors responding to the high consumer demand increased production all year, driving supplies down.

"It's looking like there's going to be a shorter supply of fish next spring than there was this spring," Cooper said. "That's good for prices, but doesn't help if you don't have any fish."

Steeby said pond bank prices at 75 cents are slightly down from the 80 cents paid by most processors since spring, and likely will stay there for the rest of summer. Mississippi processing is ahead of last year, with almost 11 million pounds processed the last week of July, about 400,000 pounds ahead of the same week in July 1998.

Food size catfish supplies are up 9 percent from last year, but the increase is in the smallest size category. The numbers and weight of fish 1.5 pounds or larger is actually lower than a year ago, Steeby said.