JELLYFISH appear regularly in Jersey’s waters, but some Islanders say they have seen more than usual this year…
Chris Isaacs, a marine expert with the Société Jersiaise and member of the government’s Natural Environment team, said he too had heard ‘reports of high numbers of jellyfish at the moment’ – a rise which could be caused by increasing sea temperatures and ocean acidification.
However, he added: ‘Most summers we get lots of jellyfish turning up in our waters.
‘We know very little about the numbers in our waters or how they are behaving, so it’s difficult to provide clear answers.’
Explaining the reasons for this summer’s increased number of reports, Mr Isaacs said: ‘Jellyfish are weak swimmers, so their dispersal is strongly influenced by currents and weather conditions. Once they arrive in our waters, we have a gyratory current which is likely to keep them circulating around Jersey.
‘They can accumulate in sheltered bays which are not swept by strong currents, but these areas are also prime swimming and diving spots, so there are more people present to report them.’
He continued: ‘An onshore wind and swell can concentrate them in one area and push them up onto the beach, so stranding reports can also give a false impression of numbers.
‘Jellyfish swarms are being reported more frequently worldwide. The reasons why they swarm are complex and cases have been linked to warming seas, overfishing, and ocean circulation patterns.
‘We may well be getting more this year and it may be linked to the same factors, but there is insufficient data from local waters to form any conclusions. If more people reported their sightings, this may give us more insight into what’s happening.’
