Keep your eyes peeled for alien invaders
Animals and plants that have been introduced to a place where they do not naturally occur are known as non-native species. Many of these live happily in the UK without causing a problem but a few become what’s called invasive.
Invasive species upset the balance of the ecosystem as they may be bigger, faster growing or more aggressive than the native species. They may also have fewer natural predators to control numbers. The native species are often unable to compete and fairly quickly the invasive species take over.
Wireweed (a seaweed from the Pacific) and Slipper Limpets (from the western Atlantic) are already well established within Cardigan Bay SAC but there are more threatening species on the horizon. The Carpet Sea-squirt (Didemnum vexillum) is a highly invasive non-native marine animal that could threaten conservation, fishing and the shellfish industry and has triggered a rapid response species alert.
Thought to be originally from Japan, it has become a pest in other countries by smothering native species and interfering with fishing, aquaculture and other activities. It has recently been found in some marinas in England, Wales and Ireland and there are strong concerns that it will spread more widely, as it travels easily on the hulls of boats. The government’s risk assessment states:
“If introduced into Special Areas of Conservation (SACs), Didemnum vexillum could have a disastrous effect on species diversity leading to habitat destruction.”
As well as the risk to the environment and fisheries, the fast-growing carpet sea squirt can cause problems for boat owners too, fouling hulls, engines, moorings and other structures.