Red swamp crayfish arrive: Invasive species vexes residents

DOVER — At home, minding his own business in the wake of a recent rainstorm, Chris Kelsch’s attention was grabbed by a sudden “click-clack” noise coming toward him up his driveway.

“It was the clacking sound of a shell on the concrete, so I looked up and it was a crayfish coming toward me,” he said. “So, I took out a shovel — I wasn’t going to hit it or anything — and put it down in front of him to scoop him up. But when I did, he raised up his claws and charged the shovel. Then he climbed up it and was trying to jump up the handle and attack me. I shook it off and stepped back a couple feet. Never in my wildest dreams would I think I’d be attacked by a crayfish in my driveway.”

Over the past six months, Mr. Kelsch has been having similar run-ins with these crayfish near his home in the Fieldstone Village development north of Dover. Quick to note that he’s not complaining or claiming an infestation, he said he finds it comical, albeit slightly alarming, how aggressive these particular cantankerous crustaceans are.
“I pulled into my driveway in my car one day and one of them actually charged at my car,” Mr. Kelsch laughed. “I saw him jumping at and trying to pinch my tires multiple times, then he was flipping himself over repeatedly with his tail. I was like: ‘What the heck is up with these guys?’”

Reporting the sightings and submitting photos to a Kent County commissioner and the state’s Department of Natural Resources and Environmental Control, the critters were quickly identified as red swamp crayfish — an invasive species well-known for its pint-sized aggressive antics. With the ability to get up to about 5 inches long, the red swamp crayfish — which looks to some like a miniature lobster — can be easily identified by the raised bright red spots that cover their bodies and claws, said DNREC wildlife biologist Edna Stetzar. According to the agency, DNREC had received reports of the crayfish in that development in 2014 and 2015 as well.

Rick Otis, a neighbor who’s lived in the development longer than Mr. Kelsch, says he’s seen the crayfish multiple times as well, specifically since the county did some sewer line work in the area a year ago.
“We haven’t seen too many, not like they’re overrunning the place,” he said. “But the neighbors who live closer to the retention ponds and marshy land see them more often.”

For his part, third district Kent County Levy Court commissioner Allan Angel was surprised.
“I’ve lived here since ’64 and this is the first time I’ve ever seen or heard of one in Delaware — it was pretty interesting to see,” he said.
According to Ms. Stetzar, the species originally hails from the Southern U.S. and has a bit of a mysterious history in Delaware.

“The Division of Fish & Wildlife first started receiving reports of red swamp crayfish from the public about eight years ago, but they likely already had established populations at that time,” she said. “I believe that rainfall and flooding cues them to move — possibly because their burrows get flooded or it’s an instinct to disperse. We have noticed that when there are heavy rainfall events, public sightings of this species increase. It is more likely that the crayfish populations were already established but people notice them more when they are moving around. The rainfall and flooding also gives them the avenue to invade new areas.”

Though it’s unknown how and when exactly they hitched a ride to the first state, the fact that they’re widely available as seafood, aquarium stock and even bait has helped them spread to many states (and even Europe) where they’re not a native species.

The red swamp crayfish’s arrival poses a number of unique threats to native flora and fauna, explained Ms. Stetzar.
“They are able to out-compete native crayfish because they are more territorial and aggressive and more tolerant of poor water quality,” she said. “They can also be vectors for fungus and viruses that infect native crayfish, although we do not have any data on this occurring in Delaware.”
Assessing the impact to native crayfish has been difficult though because little is known about these populations.

“I’m not certain that a complete inventory of the state has ever been conducted, but the most well-known native species is the White River crayfish,” Ms. Stetzar said. “Other Delaware native species that have been documented include: devil crayfish, Appalachian Brook crayfish and spinycheek crayfish. I am not aware of any targeted research in Delaware evaluating the distribution, abundance or health of these populations. I’m also not aware of ongoing research on Delaware’s native crayfish populations that would allow us to assess the impact of the red swamp crayfish invasion.”

Though the main concern is their potential impact to native crayfish and the “aquatic food web,” their burrowing activities can also contribute to “bank erosion” in the bodies of water they live in, said Ms. Stetzar.
As far as red swamp crayfish population and distribution in the state, little is known beyond the documented reports of residents.

“Most of what we know about their distribution is from public sightings and incidental encounters with red swamp crayfish by Division of Fish & Wildlife staff while conducting fieldwork (targeting other species),” said Ms. Stetzar. “We can’t really confirm based on that information that they are spreading. Public sightings are valuable but they are biased because not everyone who encounters a crayfish will report it, and red swamp crayfish could occur in remote areas not frequented by people. It is also possible that people are just more aware of this species now than they were eight years ago. However, based on their ability to disperse, it is likely that they have spread — especially during wet periods with flooding.”

DNREC reports that there have been sightings in all three counties in the state, but they seem to cluster toward the bay.
“We have not received reports of red swamp crayfish in water bodies or tributaries that are part of the Chesapeake Bay watershed, so all of the confirmed occurrences as of now are in the eastern half of the state,” said Ms. Stetzar.

What to do?
At present, DNREC is only able to monitor the situation, Ms. Stetzar explained.
“Controlling the invasion in the first place (and then the spread) is the ultimate goal,” she said. “Prevention is really the best defense with any of these species, and that is why educating the public is so important. Once red swamp crayfish invade an area, it is extremely difficult and costly to eradicate them, especially an aquatic species. It is also near impossible to conduct a controlled eradication effort that would only kill red swamp crayfish.”

To some degree, this deputizes residents to both report sightings and even dispatch the invaders if possible.
“Killing them is one way of removing them, and a person can consult a veterinarian for advice on humane disposal,” said Ms. Stetzar. “If a person is not comfortable with that scenario they can leave them where they found them. The main issue is that people do not move them around from water body to water body. The Division of Fish & Wildlife appreciates the reports that we receive from the public, and the information is added to our statewide database designed to track the occurrence and spread. This information is shared among jurisdictions in the Mid-Atlantic region via the Mid-Atlantic Panel on Aquatic Invasive Species. It’s important to share data and research any emerging threats with surrounding states.”

One rather creative response would be to eat them. But, Ms. Stetzar said some forethought would be required in this instance.
“They are commercially cultured in the southern U.S. as food and there are no laws in Delaware that I am aware of that makes it illegal to possess them or keep them to eat,” she said. “However, if a person wants to trap them, they would have to follow the regulations that pertain to baited traps. In some cases they can easily be picked up (carefully, of course) off the ground or netted. There is no official recommendations about whether or not to eat ‘wild’ caught red swamp crayfish, but common sense should prevail. If they come out of a water body that has a fish consumption advisory or that has a potential to be contaminated, then I personally wouldn’t eat them.”

Mr. Kelsch, for one, won’t be eating any crawdaddy jambalaya anytime soon.
“You couldn’t pay me to eat one,” he said. “When I posted a picture on Facebook, all my friends said ‘Let’s have a party and eat them.’ — No, not me. These things are living in the gross water in the retention ponds with runoff from the parking lot and all kinds of lawn chemicals and probably sewage. No, thanks. I’ll pass.”

He will be keeping his eyes open for the critters though, lest they sneak up on him.
“If you’re an elderly person just walking your dog and you come across one of these guys, they’re not walking away from you — they’re coming at you,” he said. “It’s no joke, because they might be small, but they’re lightning fast and they mean business. If you get within a few feet of them, they’ll put up their claws and they’re ready to rumble. They charge.”

To report red swamp crayfish sightings or concerns, call 302-735-8654 or email For an authoritative identification, a photo should be provided.

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