新托福阅读材料：Invasive 'killer' shrimp found at two sites in Wales

散养外来生物在本地生态环境是非常不负责任的行为

A "killer" shrimp that feeds on native counterparts, young fish and insect larvae has been found at two sites in Wales, says the Environment Agency.

The predatory Dikerogammarus villosus alters the ecology of habitats it invades, and can cause extinctions.

It was found in the UK at a reservoir in Cambridgeshire in September.

Environment Agency Wales said it has now been confirmed at Cardiff Bay and Eglwys Nunydd Reservoir in Port Talbot. It is not known how it arrived there.

Originally from the steppe region between the Black Sea and the Caspian Sea, D. villosus has spread across most of Western Europe during the last 10 years.

The alien invader can be as small as 3mm but may grow up to 30mm long, making it much larger than native freshwater shrimp.

Dubbed the killer shrimp by biologists for its appetite, it often kills its prey and leaves it uneaten.

Spreading

The Welsh Assembly Government has set up an all-Wales group to contain the species as much as possible.

It includes Environment Agency Wales, the Countryside Council for Wales, Cardiff Harbour Authority and the owners of Eglwys Nunydd.

People using the waters are urged to clean and dry equipment when leaving the water to prevent the species from spreading.

Environment Agency Wales director Chris Mills said: "Despite the fearsome name, these are not a threat to people, but the damage they can cause to our environment here in Wales is a very real danger.

"Because of what they eat and the rate that they eat it, it can alter the food chain and our ecosystem by increasing the competition for food and the native species that rely on the insects could go elsewhere.

"We will continue with our monitoring work across Wales to identify any other water recreation spots where they could be to see how widespread the problem has become."