AN UNLIKELY INVADER
We have the chestnut leaf miner, ash die-back fungus, and now the unlikeliest invader of all, the demon shrimp! Its name may sound like a contradiction in terms, but this tiny crustacean, first found in Britain last October in the River Severn in Worcestershire, is a voracious predator of other small creatures. There are worries about the effects it will have on fish eggs and fry, and on aquatic plants upon which it also feeds. Once established (and it is spreading) it is likely to have profound and unwelcome impacts on other wildlife.
Demon shrimps (their real name is the more prosaic Dikerogammarus haemophaphes, but that's never going to grab any headlines) are related to crayfish but are much smaller. They are about 18mm long, various shades of brown, are curved and flattened from side to side. They breed prolifically, females laying up to 300 eggs per year.
So how did this tiny shrimp get to, amongst other places, the River Severn and the Grand Union Canal from its native waters around the Caspian Sea? Two factors are implicated. The first is a canal opened in 1992 connecting two of Europe's great rivers, the Main (a tributary of the Rhine) and the Danube. This enabled the shrimp to spread into Western Europe apparently faster and more successfully than its natural enemies. It is a prime example of unintended consequences arising from a major transport infrastructure project.
The second is the practice of discharging ballast water in ships' tanks from one part of the world in another, thus providing free and easy transport for potentially harmful plants and animals. The Angling Trust is calling for the Government to immediately ratify an existing international convention designed to prevent this happening. I have referred several times in this column to David Cameron's desire to head the 'greenest Government ever' - well this is an easy thing to do that will contribute to that. No doubt vested interests in the shipping industry will persuade him otherwise, businesses do not like environmental regulations affecting trade.
In the meantime it is up to boaters and anglers to fight a rear-guard action to limit the shrimp's spread by cleaning and drying their equipment and clothing after visiting rivers and canals. Environment Agency Central Region Fisheries and Biodiversity Head Dr Ian Hirst, quoted in Total Coarse Fishing News, said: "It (the shrimp) can cling to wet nets and waders and, in cool damp conditions, still be alive a week later. We are asking everyone to follow our Check-Clean-Dry code: checking their equipment for strange organisms, wherever they've fished, cleaning them off, and DRYING the kit thoroughly. (See www.nonnativespecies.org/checkcleandry for more information.)
Demon shrimps are tiny, and may or may not be demonic, but they demonstrate why proper environmental impact studies are needed for major civil engineering work like the canal mentioned above. They are not red tape, they are a necessary precaution.