The Asian shore crab, from the Far East, was last spotted in Guernsey in 2009.
However, it has suddenly started breeding at an alarming rate in Jersey.
The species – Hemigrapsus sanguineus – can cut the number of common shore crabs due to its high reproductive rate and opportunistic nature.
Guernsey Biological Records Centre manager Jane Gilmour said there had not been any recent records of Asian shore crabs locally.
'As far as we know our shore crabs are safe, but now we know they're in Jersey they will be monitored.
'The biggest problem is that we don't know what we will do if they are seen here.
'We just have to hope that we're not going to see them, but it is a very difficult situation when something is that invasive.'
