LITTLE ROCK, Ark. — The mystery of what killed tens of thousands of fish that washed up along the Arkansas River late last year can't be solved, state wildlife officials announced Wednesday, but they do have a theory about what caused birds to fall out of the sky in a small Arkansas town on New Year's Eve.
The Arkansas Game and Fish Commission issued separate news releases on the Dec. 29 fish kill and the New Year's Eve event in which red-winged blackbirds began raining down, evoking images of the apocalypse. The agency issued the releases after autopsies and multiple tests were conducted on the fish and birds.
Scientists determined it's likely that unusually loud noises reported before the birds began falling frightened them so much that they flew off in the dark, even though they have poor night vision and typically do not fly at night. The Fish and Game Commission also said New Year's Eve fireworks likely led the birds to fly at a lower-than-normal altitude and into buildings or trees. It's estimated that 4,000 to 5,000 birds fell before midnight.
Less is known about the fish kill. None of the tests conducted on fish or water samples from the area turned up anything conclusive, the agency.
Tests on the birds, meanwhile, revealed hemorrhaging consistent with blunt-force trauma. And the agency said radar images show flights of blackbirds on two occasions on New Year's Eve suddenly taking off from a roost at Beebe estimated to contain 1.6 million birds.
"In most instances, such traumatic injuries in wild birds are due to flying into stationary objects such as trees, houses, windows, power lines, towers, etc.," a report from the Southeastern Cooperative Wildlife Disease Study, which is part of the University of Georgia's College of Veterinary Medicine, said.
The tests ruled out bacteria, viruses, heavy metals, pesticides and chemicals used to kill birds as causes of death.
The fish kill stretched about 17 miles downstream from the Ozark-Jetta Taylor Lock and Dam, and included about 83,000 freshwater drum and 1,000 other fish, including yellow bass, white bass, bluegill and sauger.
"Fish kills are not that uncommon," said Game and Fish Commission district fisheries supervisor Bob Limbird. "But kills of this magnitude in Arkansas are rare."
Fish collected from the kill were sent to the aquaculture center at the University of Arkansas at Pine Bluff, which ran tests for diseases and parasites. "We can say conclusively that the drum were not killed from a bacterial or viral infection, or from parasites," said Game and Fish Commission fish pathologist Kelly Winningham.
The Arkansas Department of Environmental Quality also conducted tests on fish and water samples. 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, according to the agency. The drum sample did not show any toxins.
Winningham said fish kills can occur for many reasons – stress, starvation, water pollution, disease, parasites, toxic algae, and severe or extreme weather.
"Unfortunately, we probably will never know exactly what killed these fish," said Game and Fish Commission assistant fisheries chief 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."