No easy answer to August flooding effect on crawfish season

(10/19/16) BASILE, La. – There is no easy answer to how the August flooding may have affected the upcoming crawfish season, LSU AgCenter experts told crawfish farmers at a meeting on Oct. 18 attended by 60 people at Toups Crawfish.

“I can’t tell you across the board if your field is going to be affected or not,” said Ray McClain, LSU AgCenter aquaculture researcher.

He said backwater flooding, with poor water quality that persists for more than a week, is more harmful than short-duration flooding from rainfall.

McClain said he is hopeful that the wet summer before the flooding gave a boost to the crawfish broodstock survival that could offset losses from the flood.

He said flooding that overtopped levees brought small fish into the fields that will eat young crawfish. A small sunfish can eat a sack of crawfish, McClain said, but the fish can be eliminated by draining fields. Prompt draining also helps maintain forage plants needed to feed crawfish, he said.

Mark Shirley, LSU AgCenter and Louisiana Sea Grant fisheries agent, said a 10-inch flood of good quality water is adequate now, but fields should be partially drained and refilled if oxygen levels fall too low.

Greg Lutz, LSU AgCenter aquaculture specialist, said testing water for oxygen and surveying fields for young crawfish are essential. “You cannot manage what you don’t measure,” he said.

Shirley said he visited a field in Vermilion Parish recently that had different sizes of crawfish, which indicates the field should have a continuous supply of crawfish for harvest during the next several months.

He said crawfish that burrowed into the levees above the water line to lay their eggs cannot emerge from the ground in the fall until rain softens the soil.

McClain said the August flooding may have forced crawfish to leave their burrows earlier than usual, interrupting the spawning process. “All kinds of bad things can happen if those females are forced out of the burrow prematurely,” he said.

Young crawfish could die in low quality water from backwater flooding, he said, although mature females can survive for a while by exiting the bad water.

McClain said a field with a large population of crawfish is undesirable. “The more crowded those crawfish are, the slower they are going to grow and reach market size,” he said.

Shirley said a field with a medium population of crawfish should have 10-15 traps per acre, while a high population of crawfish will justify 18-22 traps an acre.

McClain said any crawfish caught after Jan. 1 will not have enough time to produce marketable offspring, so harvesting should not be suspended or delayed if a few females with eggs are caught.

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Water is pumped onto a field for crawfish near Krotz Springs. Crawfish producers are eager to find out the effects of the August floods on their crop. Photo by Craig Gautreaux

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Greg Lutz, LSU AgCenter aquaculture researcher, far left, talks about the need to monitor oxygen levels in crawfish ponds. Lutz was among LSU AgCenter crawfish experts who spoke at a meeting near Basile on the possible effects of the August flooding on this year’s upcoming crawfish season. Photo by Bruce Schultz

10/19/2016 8:23:00 PM
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