Parasite is killing fish

Published 10:54 pm Wednesday, February 24, 2010

SELMA — Fish are dying in the East Selma Fish Pond, but a fix is on the way.

The fish have contracted Ichthyophthirius multifilis, also known as Ich or “White Spot Disease.” It’s a parasite that many freshwater fish farmers and some aquarium owners have dealt with at some time or the other.

“Catfish farmers get it all the time,” said Elton Reece, director of the Selma Recreation Department.

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Last week Reece and some others transplanted live catfish into the pond, which opens every spring for public fishing. The catfish placed in the pond weighed anywhere from 1 1/2 to 12 pounds.

At the time Reece noticed some catfish floating on top of the water. But a few dead fish through the winter didn’t appear uncommon, he said, so they placed the live, healthy fish in the pond.

On Monday Reece returned to the pond and found about 200 dead catfish. “Most of them were from last year,” he said.

Reece called Bill Hemstreet, also known as “Dr. Catfish.”

Hemstreet is an advisor in the Auburn University Department of fisheries and Allied Aquacultures. He works at the Alabama Fish Farming Center in Greensboro in fish disease diagnostics and control for the West Alabama catfish farming industry.

Hemstreet acknowledged the pond’s fish kill as a result of Ich and that it’s treatable. the pond should be ready for opening at its usual time in the late spring.

“It’s the largest protozoan known to science,” Hemstreet said.

The disease appears on the fish’s body as white dots, which could join together to form white patches under the slime layer of the fish’s body. Ich irritates the fish to the point that some of them rub against rocks or gravel.

Ich has three life stages. When the parasite is visible it is nearly fully developed and called a trophont, which feeds on the fish’s body flid for several days. Then, a fully developed tomont drops off and swims before it attaches to a plant or some other hosts. It divides rapidly and in a few days new organisms called swarmers burst from the cysts that have formed. Swarmers have to find a host in a few days or they will die. Once it finds a fish, it burrows in and becomes a trophont. The cycle begins again.

“This spreads very rapidly,” Hemstreet said.

The fish specialist has recommended copper sulfate to treat the fish in the Selma pond. Copper sulfate stays in the water one to four hours at the most, so Reece will have to use a number of applications to rid the pond of Ich, Hemstreet said.

Even the chemical could result in more fish deaths before the pond is cleared of the parasite.

Hemstreet said the treatment is similar to chemotherapy. If too much is applied, it will kill the patient.

“You have to hit that happy sweet spot,” he said, adding he hopes most of the fish will survive.

Those who fish in the pond shouldn’t worry. The parasite is ugly and kills fish, but “you could strip off the skin and the meat would be fine,” Hemstreet said.