A colony of crayfish has been discovered in Devonshire Marsh, sparking fresh warnings about invasive species.

In the latest edition of the Envirotalk Newsletter Mark Outerbridge, a senior biodiversity officer with the Department of Environment and Natural Resources, said that Florida crayfish were found in the wild this month.

“Acting on a sighting reported by a member of the public, baited traps were set in various locations around the periphery of Devonshire Marsh in late October,” Dr Outerbridge said.

“After a short soak the traps were hauled and found to contain several freshwater crayfish that have been identified as Procambarus alleni — the Florida, or Everglades, crayfish.”

Specimens were sent to specialists overseas, who later confirmed the identification.

Dr Outerbridge wrote: “Efforts are being made to determine how much of the marsh is inhabited by this new invader and if they have spread to other freshwater wetlands.

“Crayfish have been imported for many years by local pet shops, but this is the first time that any have been spotted in the wild.

“It is not known if they were deliberately released by an irresponsible pet owner or if the colony was founded by animals which escaped from a pond or aquarium tank, but regardless, there is strong evidence indicating there are quite a lot of them in the marsh.”

In the wild, Florida crayfish vary in colour from brown-tan to blue, but the species has been selectively bred in the pet trade to be a bright cobalt blue.

Dr Outerbridge said mature males and females were found in several locations along Vesey Street, Middle Road and Pond House Lane.

Dismembered pincher claws and pellets containing shell fragments were also discovered in grassy areas near the marsh, which suggested that local predators, most likely yellow crowned night herons, had been feeding on the invasive crustaceans.

“These herons prey on local crabs and are very adept at dismembering their more dangerous parts, the claws, before eating them,” Dr Outerbridge wrote.

“The herons also regurgitate pellets to get rid of the indigestible bits of their prey like shells, bones and fur.”

He added that crayfish burrows had been found adjacent to a draining ditch on the periphery of the marsh.

“These crustaceans create underground burrows to avoid predators, prevent drying out during droughts, and to raise their young inside,” Dr Outerbridge said.

“Some of the trapped males were in breeding form, leaving no doubt that this colony is reproducing.”

Dr Outerbridge said it was too early to tell what impact the crayfish may have on Bermuda’s environment but noted that another crayfish species, the red swamp crayfish, was included in the 2021 Invasive Alien Species Act, prohibiting its importation to the island because it was a known invasive species in many other countries.

“Given this most recent finding, DENR will be reviewing and amending the Act to limit any other freshwater species commonly found in the global pet trade from potentially establishing themselves in Bermuda,” he said.

“Discussions about possible control methods are currently under way between DENR and the various landowners of Devonshire Marsh.”

Dr Outerbridge said that a number of invasive species had been introduced to the island, both accidentally and deliberately.

“Those that become naturalised can displace native species, alter ecosystems and create problems for us,” he added.

“Everyone has a part to play in protecting the environment from the impacts of invasive non-native species.”

Dr Outerbridge urged the public to be careful with non-native pets and plants to make sure they are not released into the wild, and called on the public to report any unusual plant or animal sightings to environment@gov.bm, ideally with photographs.