“In some fields, there has been more than a 50% reduction in the overall crawfish catch.”

By Meghan Overdeep
April 29, 2021

A slimy new stranger that experts say could threaten this year's crawfish season has taken up residence in St. James Parish, Louisiana.

LSU AgCenter entomologist Blake Wilson called the masses of invasive apple snail eggs popping up in the area "the densest he's ever seen."

He became aware of the situation last week after receiving a call from a St. James crawfish farmer who was concerned by the appearance of the apple snail's dreaded bright, pink eggs.

Wilson believes severe weather and flooding over the last year could have contributed to its eastward spread from Texas and other western Louisiana parishes.  

"It's likely they may have shown up on new farms following the hurricanes last year," Wilson, who specializes in agriculture pest management research, said in a release issued by LSU AgCenter. "Any type of flooding can create an easy way for them to get into isolated ponds."

Apple Snail Eggs Louisiana
Credit: Blake Wilson/LSU AgCenter

It's currently estimated that fewer than 3,000 of Louisiana's 200,000 acres of crawfish farms have been affected, but those that are have reportedly been hit hard.

"They're catching half the normal crawfish due to mature snails both clogging trap entrances and consuming the bait," Wilson said of the impacted farmers. "In some fields, there has been more than a 50% reduction in the overall crawfish catch."

Introduced to the Louisiana ecosystem by irresponsible pet owners around 2016, apple snails were previously sold as "Mystery Snails," "Island Snails," and "Giant Apple Snails." These mollusks reproduce quickly and can wreak considerable damage on natural systems.

Crawfish Boat with Apple Snail Eggs
Credit: Blake Wilson/LSU AgCenter

Fortunately, mature apple snails aren't all that good at moving across land without accidental help from humans or the aid of natural flooding occurrences.

"A main point I'd like to emphasize is not to move boats and equipment from infested bodies of water to those that are not infested," Wilson said. "Anything near the surface of the water can get an egg mass on it and they can be introduced that way."

The bodies of adult apple snails can be two inches wide to three inches tall with the shell extending up to six inches—comparable in size to an apple, which is how they got their name. Their bright reddish-pink eggs are easy to identify and are laid in glob-like in groupings of 200 to 600.

Jacoby Carter, a wildlife ecologist at the U.S. Geological Survey Wetland and Aquatic Research Center in Lafayette, said that the best way to destroy the eggs in their first, bright pink stage is by scraping them into water, where they cannot survive or hatch. Once they have started to develop and turn white, it's best to crush them.

"Eventually, we might be able to identify a solution, but it's not going to be a silver bullet," Wilson said. "The best method of prevention is for farmers to remain aware, use controlled flooding with well water when possible and to clean their equipment thoroughly before transferring it from pond to pond."