SWARMS of spider crabs – being fuelled by rising sea temperatures – have decimated Jersey’s mussel crops and are threatening stocks of brown crabs and lobster.
The ‘prolific and aggressive’ crustaceans have recently destroyed shellfish farms in Normandy and Brittany, and caused such a problem locally last summer that the Jersey Oyster Company has decided not to seed mussels this year.
Chris Le Masurier, from the company, which is the only producer of mussels in the Island, said that he wanted to see how French farms cope with the predatory threat of spider crabs before trying to grow mussels again.
He said: ‘On the basis that spider crabs are migratory – they came into Grouville Bay in huge numbers last year, did damage and then moved off – I’ve made the decision not to-reseed the mussels.
‘There’s different techniques and measures being trialled by the French mussel farmers, so I’m leaving the French fishermen to do the trial work.’
Mr Le Masurier added that he hoped the reduction in food for them this summer would mean that the spider crabs were less likely to return next year.
‘I’m hoping that they won’t bother coming back to Grouville Bay again,’ he added.
Mr Le Masurier said that mussels were highly popular among his customers and the decision to not plant seeds would mean two years without sales of the shellfish.
Currently all mussels which are sold in Jersey are imported from Scotland with the Jersey Oyster Company’s stock being exported to France.
Gabby Mason, of Jade-S Fisheries, said: ‘In the past they were more seasonal but we’re seeing them throughout the year now. It’s meant to be their off season now, but they’re still around. We are really seeing an increase in spider crabs.’
Meanwhile, environmentalist Bob Tompkins confirmed it was highly likely there were a growing number of the species in Jersey waters as a result of warmer waters caused by climate change.
Mr Tompkins added: ‘As sea temperatures have increased, spider crabs have moved north. As a result, chancre crabs have decreased with one of the reasons being they are a colder water species.’
Jersey Fishermen’s Association president Don Thompson said that spider crabs can be an issue for fishermen due to their ability to ‘move rapidly and eat all day’.
‘Everything competes for food at sea. We’re seeing an unprecedented level of spider crabs on the ground and they’re having a negative impact on other species such as [brown] crabs and lobster. Anecdotally, as spider crab stock increases, crab and lobster stocks have decreased.’
Mr Thompson added: ‘There’s a lack of a good market for spider crabs in Jersey and we’re throwing back 200 to 300 kilograms of spider crabs into the ocean per day. They are quite a valuable commercial species, but we don’t have any good markets for them.
‘The sheer volumes of spider crabs caught in the Brittany fleet was around 4,500 to 5,000 tonnes in 2021.’
In Jersey the market for spider crab is limited to small summer markets, according to Mr Thompson, who added exporting the species would create an ‘unbelievable hassle’ due to the financial and administrative implications of Brexit.
Mr Le Masurier added that his oysters – which are protected from crab attacks – were ‘looking extremely healthy this year’.
He added: ‘They are not accessible to spider crabs because they are protected by mesh sacks.
‘Its been very encouraging and we hope that excess oyster production will compensate for the loss of mussels.’
