Boat users and anglers across Ireland were put on alert for killer shrimp which threaten local wildlife.
Insects such as damselflies and water boatmen could be at risk, with knock-on effects on species which feed on them, conservationists said.
The shrimp, which has spread rapidly through western Europe in recent years and was discovered in England this month, pose no risk to drinking water supplies, but anglers and boat owners were being urged to make sure they do not transfer the species.
Northern Ireland Environment Agency spokesman John Early said: "We are asking water users to be vigilant and protect our lakes and rivers from new introductions.
"The recent arrival of the killer shrimp in Britain has highlighted the need for water users to clean equipment and boats before moving to another water body."
The shrimp, known as dikerogammarus villosus, were found by anglers at Grafham Water reservoir in Cambridgeshire.
It is a voracious predator, killing a range of native species, including freshwater invertebrates and even young fish.
The crustacean, which kills its prey and leaves it uneaten, tends to dominate habitats, sometimes causing the extinction of native species, experts said.
Invasive Species Ireland has advised that all water should be drained from boats, equipment and kit before leaving any water body.
They also advise that boats and equipment should be disinfected between each use as this will help to keep the killer shrimp and other aquatic invasive species out of Ireland.