The following is a press release from the LSU Agcenter:
Over the next several days, Tropical Storm Lee will drench most of Louisiana's crawfish-producing parishes with rainfall ranging from several inches to possibly more than 20 inches in some isolated areas.
The time for fall flooding of crawfish ponds is fast approaching, but even though this is "free" water for crawfish farmers, with no pumping costs, it may cause many producers to lose crawfish due to subsequent poor water quality or require them to spend a small fortune to keep oxygen in their water for the next four to six weeks, according to LSU AgCenter crawfish expert Greg Lutz.
"Poor water quality is often a serious problem in crawfish ponds after tropical storms and hurricanes have passed," Lutz said. "A fundamental problem with flooding crawfish ponds this early in the fall is that the warmer water is, the less dissolved oxygen it can hold."
In the coming weeks, daytime temperatures will be hot once again, and trying to maintain suitable oxygen levels through pumping and flushing will be economically impossible, he added.
This time of year, it is better to drain storm water out of crawfish ponds as soon as possible, said LSU AgCenter aquaculture specialist Mark Shirley. If a field has rice or rice stubble, crawfish producers are encouraged to hold no more than a couple of inches of rain water to help the plants continue growing during September and early October.
"If crawfish producers have sorghum-sudangrass planted as a forage, those fields should be drained completely, and as soon as possible," Shirley said. "Ponds with wild vegetation like grasses and sedges should also be completely drained."
Both experts point out, however, that one problem with this strategy is that ditches, canals and bayous usually used for draining crawfish ponds can be filled by the same excessive rainfall that floods the ponds. In these circumstances, the best strategy for crawfish producers is to raise their standpipes before the water rises to keep wild fish and other predators from entering their ponds through the drainage system.
Once water levels begin to recede, crawfish producers should avoid the urge to hang on to all that "free" water, Shirley emphasized. "Ponds should be drained as quickly as Mother Nature will permit."
Mature crawfish spend the summer in underground burrows. According to Lutz, the majority of the female crawfish in burrows this time of year will lay their eggs later in September and on into October.
Typically, only a small percentage of female crawfish spawn in early September, so even if some crawfish are crawling around right now, the majority of the carryover or stock crawfish in most ponds should still be in the ground, Lutz said.