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Cause of Arkansas River fish kill still unknown

Date01/26/2011
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OZARK - Despite a battery of tests conducted by the University of Arkansas at Pine Bluff, the exact cause of the Arkansas River fish kill that took place on Dec. 29, 2010, still eludes biologists at the Arkansas Game and Fish Commission.

A resident of Roseville first reported the fish kill near the Roseville boat ramp of the Arkansas River. After further investigation, biologists determined the kill stretched from the Ozark-Jetta Taylor Lock and Dam to about 17 miles downstream. The incident killed approximately 83,000 freshwater drum and 1,000 other fish, including yellow bass, white bass, bluegill and sauger.

"Fish kills are not that uncommon," said AGFC District Fisheries Supervisor Bob Limbird. "But kills of this magnitude in Arkansas are rare."

Biologists collected several dying fish during the first few days of the kill and sent them to researchers at the University of Arkansas at Pine Bluff.

"We can say conclusively that the drum were not killed from a bacterial or viral infection, or from parasites," said AGFC Fish Pathologist Kelly Winningham. "UAPB ran a full set of fish health tests and everything came back negative."

The Arkansas Department of Environmental Quality also collected fish and water samples from the area of the kill and conducted testing. Water samples were tested for metals, nutrients and minerals to assess water quality. Fish samples were tested for metals. A drum sample was tested for toxins such as pesticides and other organic chemicals. All samples were within normal values for the Arkansas River. The drum sample did not show any toxins.

Winningham said fish kills can occur for many reasons, both natural and unnatural. Stress, starvation, water quality issues, water pollution, disease, parasites, toxic algae, and severe or extreme weather can all cause mortality. Kills also may be caused by multiple factors working in combination.

"Unfortunately, we probably will never know exactly what killed these fish," said AGFC Assistant Chief of Fisheries Chris Racey. "But the testing has eliminated the largest public concerns of disease, parasites and toxins. We have no reason to think fish caught in the Arkansas River are unsafe to eat."