Fears last week that a new species of Asian shore crab may have arrived were momentarily quelled when the specimen collected turned out to be Hemigrapsus sanguineus, which has been found in Jersey since 2009.
But the second species, Hemigrapsus takanoi or the brush clawed crab, is expected to arrive imminently, and very little can be done, Paul Chambers, the States coastal manager, has said.
‘We have the normal Asian shore crab, which has come up from the south,’ he said. ‘The other species has been spreading steadily down from the north.’
The crab already found in Jersey is a native of the Pacific which has spread rapidly worldwide and is aggressive with a voracious appetite.
There were concerns it would drive out the local shore crab but Mr Chambers said a study of its activity in Jersey found that has not been the case.
‘We were worried because in some parts of the world it has competed with our shore crab,’ he said. ‘But actually. for some reason here, these ones have stuck themselves right to the top of the shore where we don’t get many shore crabs.
‘Even though,there are hundreds and hundreds of them, they don’t seem to interact with our shore crabs.’
But other invasives have caused problems such as wireweed, which arrived in 1980 and within years was choking entire rock-pools. ‘It takes up a lot of oxygen,’ Mr Chambers said. ‘It’s an absolute nuisance.’
And an invasive bryozoan – a sedentary filter feeder, sometimes called a moss animal– has almost driven out its local counterpart.
‘We are perfectly in the wrong location for invasive species because we pick up an awful lot from Biscay, where there was a big oyster industry in the 70s,’ Mr Chambers said.
‘We also get the ones which are coming down the English Channel from big ports and we have ferries running backwards and forwards. An awful lots of things like barnacles cling to the underneath of the boat, get dropped off in St Helier and then spread out more widely.’
Mr Chambers did a comprehensive study of marine invasive species which was published earlier this year. The report estimates the number of invasives could double over the next 20 years.
