Freshwater Crayfish Found In Devonshire Marsh
We apparently have some new residents on the island, as several freshwater crayfish were found in the Devonshire Marsh area.
In a recent edition of the Envirotalk newsletter, Dr Mark Outerbridge said, “A novel species appears to have established itself on Bermuda, further adding to the list of non-native plants and animals who now call our island their home. 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.
“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 mailed to taxonomic specialists overseas who have confirmed this identification. 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 [e.g. Paget Marsh and Pembroke Marsh].
Freshwater crayfish trapped from Devonshire Marsh in November 2024. Photo courtesy of Envirotalk/M. Outerbridge
“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.
“Mature males and females were trapped from several different locations along Vesey Street, Middle Road, and Pond House Lane. Furthermore, dismembered pincher claws and pellets containing shell fragments have been found on grassy areas adjacent to the marsh, suggesting that the crayfish are being eaten by another animal – likely yellow crowned night herons.
“These herons prey on local crabs and are very adept at dismembering their more dangerous parts [the claws] before eating them. The herons also regurgitate pellets to get rid of the indigestible bits of their prey [e.g. shells, bones, and fur]. Crayfish burrows have also been discovered adjacent to a drainage 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. Some of the trapped males were in breeding form [F1], leaving no doubt that this colony is reproducing.
Discarded pincher claws from crayfish believed to have been preyed upon by yellow crowned night herons hunting in Devonshire Marsh. Photo courtesy of Envirotalk/M. Outerbridge
“It is too early to tell what impacts the crayfish may have on the local environment. A closely related species, the red swamp crayfish Procambarus clarkii, is a known invader in many other countries and for that reason was included in the 2021 Invasive Alien Species Act, thereby prohibiting their importation to Bermuda.
“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. Discussions about possible control methods are currently underway between DENR and the various landowners of Devonshire Marsh.
“Over the past 500 years Bermuda has experienced a continual procession of non-native invaders introduced by humans [either accidentally or deliberately] which have found themselves in an advantageous environment with few [or no] natural enemies. Those that become naturalized [i.e. self-sustaining in the wild] can displace native species, alter ecosystems, and create problems for us.
“Everyone has a part to play in protecting the environment from the impacts of invasive non-native species. Here are three simple things that you can do:
- 1. Be plant wise and do not let your garden, pond, or aquarium plants enter the wild.
- 2. Take care of your pets, never release them, or allow them to escape into the wild. It is cruel to them and could harm other wildlife.
- 3. Report any unusual animal or plant sightings to environment@gov.bm [good quality photographs are particularly welcome].”
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