I have received a flood of emails lately from people complaining about the sudden explosion of crayfish in their yards this year. The worst cases seem to be in yards that flooded last year, either from nearby construction, which altered drainage, or from Tropical Storm Imelda.
The most common complaint: the mud chimneys make mowing yards nearly impossible. And, “You can twist an ankle without even trying,” says Gretchen Dunlap Smith, one of the affected homeowners. On an even more serious note, they can also undermine earthen dams. “What to do?” people ask.
Be Thankful You Don’t Live in Tasmania!
Crayfish, crawfish, crawdads, mudbugs, whatever you call them, they’re all essentially the same thing. More than 550 species exist worldwide. They range in size from less than an inch in Louisiana to more than 8 POUNDS in Tasmania. There are 390 species in North America, 338 in the United States. Texas alone has 40 species according to Texas Parks and Wildlife. Counties in the north Houston area even have their own unique breed.
Attracted to Water, Danger to Pond Dams
Louis A. Helfrich, Extension Specialist; Jim Parkhurst, Extension Specialist; and Richard Neves, Extension Specialist; Department of Fisheries and Wildlife Sciences, at Virginia Tech published a study called “The Control of Burrowing Crayfish in Ponds.” They say that burrowing animals such as crayfish “construct their homes or ‘burrows’ by digging into soil banks along the shorelines of waterbodies. Tunnels dug below the water level provide channels through which water can escape. Tunnels dug above the water level can decrease structural support of the embankment and increase the risk of washout during flood conditions. These hazards are multiplied in waters where burrowing animals are abundant and where water levels fluctuate.”
Chemical Treatments Not Recommended
The breeding season peaks in early spring, say the authors. “Complete elimination is usually not possible … Control is successful when the balance between the predator (fish, birds, mammals) and the prey species (crayfish) is reached, and excessive burrowing damage is reduced to an acceptable level.”
The Virginia Tech study does not recommend chemical treatments because they: (1) threaten water quality, (2) kill beneficial plants and animals as well as pests, and (3) can be widely distributed by wind and water movements.
No chemicals are currently registered for crayfish control. Never apply toxic chemicals directly to waters or near shorelines where they can seep into waterways.”
Another homeowner, Susanne Kite says, “Places in my yard have not completely dried up since Imelda. A lot changed after that flood. I don’t understand what was so different and caused so much to change.”
Crayfish Love Wetlands
Suzanne Simpson, a wildlife biologist with the Bayou Land Conservancy, may have an explanation. “Crayfish love wetlands. So much so that the presence of crayfish mounds is considered a secondary indicator of wetland habitat on wetland delineation sheets for the Corps of Engineers.”
“Crayfish feed on detritus and mostly make their mounds during the rainy season,” says Simpson. “I’m sure the floodwaters brought in some detritus with them, and flooding leaves traces that likely lead the crayfish to identify these yards as good habitat. They’re not too easy to get rid of, but it can be done.”
Drainage Improvement and Traps: Your Best Bet. Puppies? Not So Much
You best bet: terrascaping to improve drainage, say the experts. Failing that, “traps are humane and non toxic. You don’t have to worry about poisoning other animals or leaving persistent residue in your soil,” says the web site Gardening Know How.
“My littlest schnauzer had puppies Dec 30th,” said Gretchen Dunlap Smith. “The puppies are DIGGING them up at a rapid rate and EATING them! It is GROSS hearing them crunch!! Sounds like they are chewing gravel. So, no chance for étouffée…the dogs are having sushi.”
Posted by Bob Rehak on March 30, 2020 with help from Suzanne Simpson, Gretchen Dunlap Smith and Susanne Kite
944 Days after Harvey and 193 since Imelda