Sorry to disappoint but I am not in fact talking about the arrival of little green men from the far corners of the universe, but something altogether closer to home: the invasion of alien (or invasive) species which, most certainly, do not come in peace.
An alien species is a species that has been introduced or is found outside its native distribution, and as innocuous as this may seem, alien species are a destructive threat environmentally and economically.
For a start, their impact is estimated to cost the global economy up to £914 billion a year, and in the UK alone, £1.7billion. Alien species often predate or out-compete native species, or can introduce infectious diseases and parasites. The negative impact of alien species such as the Grey squirrel are more familiar, but few people are aware of the legacy of damage they have caused on the UK’s aquatic habitats.
In the UK alone, 117 non-native freshwater species are currently established, and some of the most notable may come as a surprise to seafood and shellfish lovers…non-native crayfish!
Six alien crayfish species are currently established in the UK: the Signal, Virile, Noble, Spiny-cheek, Red swamp and Turkish crayfish, largely from deliberate or accidental introductions from populations bred for the commercial (restaurant and food) and recreational trade.
These alien crayfish have devastated the once widespread populations of our native white-clawed crayfish species and represent an ever increasing threat to the UK’s aquatic biodiversity.
In a last ditch attempt to maintain native populations, conservationists are re-homing and relocating individuals to ‘ark’ sites, which are isolated, self contained sites (e.g. abandoned quarry pits) which will hopefully support small self sustaining populations of native crayfish for the future.
“It is the lesser of two evils, better to exist in small numbers, out of harm’s way, than not to exist at all”.
So next time you pop into your local seafood restaurant and sink your teeth into some delectable crayfish cakes or curry, I hope you would spare a small thought to our humble native white-clawed crayfish and its fight for survival!
By Tabitha Jones