Thunderstorm believed responsible for kill of bass, crappie, bream and baitfish.
A fish kill that was reported on the LouisianaSportsman.com forum yesterday (July 7) is believed to have been caused by a heavy thunderstorm the previous day, the Louisiana Department of Wildlife and Fisheries said.
“The instant addition of cold rainwater into channels like the one between McGee’s Landing and Whiskey River landing and The Boulevard caused the water to turn over,” LDWF’s Mike Walker said. “This brought low oxygen to the surface, and the resulting net oxygen level was not enough to sustain fish life.”
The kill included threadfin shad, freshwater drum, largemouth bass, some bream and a few crappie in the Whiskey River channel next to McGee’s landing, Walker said.
In the channel known as The Boulevard were found thousands of dead threadfin shad that appeared to have turned belly up sometime on Thursday (July 7), he said.
“There (also) were hundreds of freshwater drum, and they looked to have died at the same time as the shad,” Walker said. “There were a few white bass, some largemouth bass and some bream.”
Click here to see other photos of the kill taken by LouisianaSportsman.com user Lane Frost.
Walker said the dissolved oxygen level in The Boulevard was 4.45 mg per liter at the surface. LDWF personnel also found dissolved oxygen levels of 5.86 and 6.72 mg per liter.
All of those readings are considered normal and could not have caused the kills, LDWF’s Melissa Kaintz said.
This led the biologists to believe the water turned over, bringing to the surface water with dissolved oxygen levels as low as 1 mg per liter after the storm. They also concluded that the water had remixed and returned oxygen levels to normal.
“We observed no pipping fish anywhere along this route,” Walker said.
The kill didn’t surprise biologists, who have known that oxygen levels have not been “very high as a whole in” Henderson since the waters in the Atchafalaya Basin began receding as the Morganza Spillway was closed off.
“Water in the northern end of the Henderson Water Management Unit has been sitting over much organic material in high temperatures of the months of May and June,” he said. “The decay of this organic material has decreased the oxygen levels in the water draining through Henderson to the only outlet.”
That apparently wasn’t a huge issue until the heavy storm of July 6.
“The primary productivity oxygen by plankton and aquatic vegetation has been able to keep oxygen levels from becoming lethal up until the thunderstorm cause the water to turn …,” Walker said.
And Walker said there could be other kills as water levels return to normal.
“There may be other fish kills occur in Henderson until all of the water to the north have drained through the lake and the primary production of oxygen does not have to overcome low oxygen levels moving through the lake,” he explained.