Scots wildlife at risk from alien crayfish breeds

A VORACIOUS alien predator has been found in Scotland for the first time after they were bought into the UK illegally.

The National Wildlife Crime Unit has recovered about a dozen marbled crayfish from home aquariums at three properties in the Central Belt, Scotland on Sunday can reveal.

Marbled crayfish, thought to be native to North America, are banned in the UK because of the severe threat which they pose to native wildlife and the environment. They are the only crayfish capable of reproducing asexually, meaning that it only takes the introduction of a single female to cause a devastating outbreak.

Sign up to our daily newsletter

The i newsletter cut through the noise

Their unusual and prolific breeding method requires huge amounts of energy which they obtain by feeding on a vast range of flora and fauna, jeopardising a wide variety of native plants and insects. The discovery in Scotland follows suspicions among experts that the lobster-like crustaceans are being purchased and kept illegally in fish tanks.

There are still no sightings of the creatures in the wild in Scotland or the rest of the UK, but the case highlights the danger to ecosystems and wildlife-related tourism.

Another non-native crayfish, the American signal, which was introduced by restaurateurs in the 1970s and later escaped into lochs and rivers where populations exploded, costs the economy around £500,000 a year, mainly through loss of income to businesses which rely on angling.

Dr Colin Bean, science and policy advisor on freshwater biology at Scottish Natural Heritage, formally identified the recovered species in the current case.

He said: “Your heart stops really because American signal are bad enough. The biggest difference between marbled crayfish and other crayfish species is that the others need a male and a female to reproduce, but marbled crayfish are parthenogenic [reproduce asexually] which means you only need one to establish a population.

“They are smaller than American signal but they can reproduce when they are only 14-22 millimetres long and as adults, which are about 10-13 centimetres, they can produce 400 [offspring] at a time.

“That in itself is likely to lead people who may buy them on sites like eBay or Gumtree to liberate them by disposing of them in lochs and rivers or chucking them down the drain, which is the danger.

“Unlike signals, marbled crayfish aren’t big enough to eat fish but they can feed on invertebrates such as mayflies which are really important in terms of biodiversity.

“If you introduce something which removes these invertebrates you will have a significant ecological and economic impact.

“In Galloway the signal crayfish has had a serious effect on fishing and the businesses which rely on that, including hotels.”

Marbled crayfish are mottled blue-green in colour. They first appeared in the aquarium trade in the mid 1990s in Germany where they were released, deliberately and accidentally, and are now found in the wild in large numbers.

In 2003 they were introduced in Madagascar as a food source and again bred prolifically to cause serious environmental issues.

The crustaceans can survive in temperate water, making the UK another suit­able location for them if they find their way into rivers and lakes.

Introducing crayfish deliberately or accidentally is seen as being on a par with polluting the environment in wildlife crime offences. Anyone caught in possession of non-native crayfish in Scotland can be jailed for up to six months and fined £40,000.

However, the NWCU said that in the cases in Scotland the offenders did not seem to know they were breaking the law and prosecutions are unlikely at this stage.

Charles Everitt, the NWCU’s Scottish investigations officer, said: “Everyone we have recovered the crayfish from has said they were unaware that they had committed an offence.

“One lady bought them online from someone in England. She kept one, which died, and gave about half a dozen each to two other people, one of whom passed some on again, so a chain developed quickly. We don’t think any have bred or escaped.”

The NWCU was alerted to the potential for illegal trading by UK government agency the Centre for Environment, Fisheries and Aquaculture Science (CEFAS), which noticed an advertisement for marbled crayfish online.

“I think the more people get into it the more crayfish will be sold online, but people in Scotland need to be aware that if they buy or sell crayfish they are breaking the law,” Everitt said. “It only takes one person to start a chain like this to create a serious risk that these creatures will escape into the wild.”

Twitter: @ScotsmanJulia