The UK’s coastal city of Brighton is generally known for its open-armed attitude towards all walks of life, unless – that is – that walk is the sideways gate of the notorious Atlantic blue crab. A visitor most unwelcome to Britain’s southern shores, local authorities have been forced to issue beach-goers and fishers with a ‘high alert’ warning over recent sightings of this invasive species.

According to the Sussex Inshore Fisheries and Conservation Authority, this colourful, beautiful, yet meddlesome species was first spotted in Brighton’s waters this summer, when a solitary Atlantic blue crab was found washed up on shore, dead.

It wasn’t until months later, however, that a second sighting was recorded this October, when another Atlantic blue crab made its presence known – this time, very much alive.

The issue is, the Atlantic blue crab is a non-native species and while not all such non-native species are harmful, some have a tendency to become invasive non-native species. It’s species such as these that then pose major threats to local ecosystems and biodiversity. In fact, invasive non-native species are currently the second biggest global threat to biodiversity.

“These crabs, with their striking white and orange claws and blue legs, are stunning but seriously out of place,” said the Sussex Inshore Fisheries and Conservation Authority in a written warning issued to locals, urging beach-goers in the area to remain vigilant.

“They’re native to the western Atlantic Ocean and Gulf of Mexico – not the English coast.”

Non-native species like the Atlantic blue crab are often introduced to new waters through human activity such as ballast water transport or accidental release. Recognising the serious threat that invasive non-native species pose to local ecosystems, the UK Government and its Department for Environment, Food, and Rural Affairs are said to be ramping up efforts to tackle the issue through its 25 Year Environment Plan, as well as through a dedicated cross-governmental group.

Within that plan, the UK government has detailed its goals to reduce the number of established invasive non-native species by at least 50% by 2030 compared to population numbers in 2020. This will also include a number of safeguarding and response measures, including better educating people on the risks of invasive non-native species and how to avoid introducing them, developing a framework for rapid responses when invasive non-native species are detected, supporting research on cost-effective methods to address established invasions, and implementing activities to reduce the impact of invasive non-native species on protected sites.

While this plan is still being developed, local authorities around Brighton’s coastline have called for extra vigilance among beach-goers and sea-farers in the area, urging anyone that happens to catch an Atlantic blue crab not to release it back into the waters (citing the Wildlife and Countryside Act 1981), but instead to “hand it in to your local Marine Management Organisation”.

For those that may spot one of these colourful crabs during their own visit to Brighton’s coastline, the Sussex Inshore Fisheries and Conservation Authority has asked for all sightings to be reported to the iRecord platform.

This isn’t the first time the Atlantic blue crab has found itself in hot water. The species is now considered by the International Union for Conservation of Nature as one of the 100 worst invasive species of the Mediterranean ocean where, in recent years, its population has exploded with “devastating effect”.

As reported by Pietro Formis in issue 39 of Oceanographic Magazine, the invasion of the Atlantic blue crab across swathes of the northern Adriatic Sea has left in its trail “far-spread devastation” within local marine habitats where the species has not only been feeding on the local population of bivalve mollusks, impacting upon local biodiversity, but impeding on the local fishing industries, too. 

Researchers believe that frequent flooding events in recent years have “played a crucial part in the crab’s demographic explosion”, with increases in fresh water flowing into river estuaries, combined with rising sea temperatures, providing “an ideal habitat for the species”. 

The Mediterranean has faced several invasions by non-native species over the decades, from lionfish in the Aegean Sea to various mollusks disrupting local ecosystems. These invasions, it is noted, have often historically led to “significant ecological shifts and economic challenges for local communities”.

Reports such as these set a precedent for understanding the impact of the Atlantic blue crab.

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