Pointe Coupee Parish residents have no reason to be alarmed by the hundreds of thousands of dead fish that washed ashore last month, and again this week, in False River, officials from the state Department of Wildlife and Fisheries say.
Brian Heimann, a department biologist, said the fish kill was just a natural occurrence primarily caused by the recent cold fronts and not an indication the oxbow lake's water quality has been compromised by contamination or isn't improving due to ongoing restoration efforts.
"This happened because of a low dissolved-oxygen situation," Heimann explained Thursday on the banks of False River, where a foul stench from the decomposing carcasses of hundreds of threadfin shad permeated the air.
Threadfin shad are tiny, grayish in color, bait fish prone to die in large numbers due to drastic changes in water temperature and dissolved-oxygen levels. Thousands of their lifeless bodies floated to False River's surface late last month and again this past weekend after overnight temperature drops from cold fronts caused the lake's stratified water to mix and deplete oxygen levels for its aquatic life.
"What you have is good (oxygen-rich) water on top and bad (oxygen-poor) water on the bottom," Heimann said. "A cold front will come through and cause the good water to sink to the bottom, pushing the bad water to the top."
The situation was further impacted by the overabundance of sediment that's now exposed because of the man-induced drawdown of False River's water level. Heimann said the exposed sediment also sucks up the lake's dissolved oxygen, making it even tougher for the threadfin shad to breathe.
"Even with the significant fish kill, they rebound dramatically," Heimann said. "We try to control their numbers anyway because we have an overabundance of them in the lake."
False River, once a premier spot for trophy bass fishing, has been in a state of decline for several decades due to heavy silt buildup at the bottom of the lake that impeded vegetation growth and curtailed fish-spawning habitats.
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Since 2012, state and local officials have dedicated millions of dollars into a wide array of restoration efforts to improve the lake's water quality and return it to its glory. The man-induced drawdown has been the most controversial effort, drawing ire last year from property owners along the lake's 22-mile shoreline who claimed the lower water levels were damaging their bulkheads.
The Pointe Coupee Parish Police Jury has implemented drawdowns twice since restoration efforts began. The events usually begin in September and end around March. This year, the Police Jury was allowed to lower the lake's water level by a maximum of 5½ feet. As of Thursday, False River's water level sat at 11 feet. It's normal pooling stage is around 16 feet.
Reducing the water level every so often reduces turbidity and exposes more of the lakebed to sunlight, helping dissolve the heavy build-up of sediment beneath the water. Drawdowns, which Wildlife and Fisheries commonly use in many lakes across the state, also increase sports fish reproduction and aquatic vegetation growth, officials say.
But parish leaders say the recent fish kill did serve as another bullet point this year for those opposed to the drawdowns.
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"I got some calls from folks asking why the fish are dying and is it due to the drawdown?" said state Rep. Major Thibaut, D-New Roads. "No one likes to look at mud off their piers and out their windows, but False River is not what it used to be, and we're trying to make it better.
"Everybody is going to have to sacrifice for a short period of time," he said. "This is about the long-range betterment of False River."
And that scenario is just around the corner.
Heimann said the scads of pelicans feeding in the lake lately are a sign things have improved.
"Normally, pelicans don't show up in such large numbers on False River," he said Thursday. "That means they're here feeding on the feeder fish, which is good."