Dealing with Molting Mudbugs on the Farm

By Patrick D. Bonin

Branch, LA. – Unlike people, crawfish can’t run out and get a new pair of pants or a brand new shirt to compensate for holiday overeating.

As crustaceans with a hard shell, or exoskeleton, the only way they can grow is by shedding their existing shell and then forming a new one, a process called molting.

“They physically grow until their existing hard shell becomes too small,” said Mark Fruge’, co-owner of Frugé Aquafarms. “It’s like us growing out of a pair of shoes. They run out of room so they kick off the old hard shell, and they come out with a soft shell that’s larger and hardens over time. That process keeps repeating itself until the crawfish reaches maturity.”

According to the Louisiana Crawfish Production Manual published by the LSU Ag Center, crawfish can increase up to 15 percent in length and 40 percent in weight in a single molt! Approximately 11 molts are necessary for a young crawfish to become mature, according to LSU.

Molting is a great sign on the farm, as it’s a solid indication the mudbugs are continually growing to a marketable size. The only potential problem occurs when a large percentage of the crawfish molt at the same time.  According to LSU, molting is hormonally controlled but can be affected my water temperature, food quality and quantity, population density, oxygen levels and other factors.

“The main issue with a molt is that crawfish typically get weak during the process of shedding their shells,” he said. “They’re not as hardy as they regularly are, because they’ve gone through a lot of stress in shedding that shell. There’s a window when they’re weak, and we need to monitor that when we harvest because their shelf life can be greatly diminished in that condition.

“There’s nothing we can do to control it, but you have to manage the situation and use the crawfish quickly when they’re in that weakened state,” Fruge’ said.

Crawfish harvested on the farm are regularly monitored for signs of a major molt, especially early in the season. Frugé said mudbugs about to molt have a darker shell and a distinct line on their bodies. Right after a molt, they’re tender and greenish or light-colored, until their new shell hardens completely, he said.

“Crawfish molt throughout the year, but you typically only have mortality issues early on in the season,” he said. “After you reach a certain point, a large percentage of crawfish are mature and are no longer growing, so the risk greatly diminishes.”