Bonito first appeared here around 15 years ago and are now being caught in ever-increasing numbers by fishermen during the summer months.
It is thought that the species, which have around 50 sharp teeth and can grow up to 8 kg in weight, are being brought to Jersey’s waters by rising sea temperatures as a result of climate change.
Paul Chambers, marine and coastal manager for the Environment Department, said that the fish were of scientific interest and any captures should be logged with Jersey Biodiversity Centre or the Marine Biology Section of the Société Jersiaise.
‘The bonito is just one of several southern European species that have entered local waters in the past couple of decades and are now becoming common,’ he said.
‘Prior to the Second World War only a handful of bonito records were known from British waters. Specimens started to be caught locally about 15 years ago and within a decade this fish was being caught by anglers every summer.
‘The bonito is considered to be a vagrant to British waters but for the Channel Islands it is now a regular summer visitor. Bonito caught locally average around 1.8 kg but this is increasing with time and further south bonito have been known to reach 8 kg.’
Mr Chambers added that some fish which preferred cooler temperatures could now be leaving the Island’s waters and moving further north. He also explained why he thought bonito were choosing to come to Jersey.
‘Fish like the bonito are probably arriving here because they are migratory fish that can swim long distances annually. The geographic range of most animals is rarely fixed and will change with time and also because local sea temperatures have risen by about 1°C since the 1960s – especially during the winter months – making the islands more favourable for southerly species.’
Earlier this summer a number of bluefin tuna were caught off Jersey’s coast.
However, Mr Chambers said: ‘Conversely, some colder water species may be decreasing in abundance as their geographic range moves northwards.’
Anyone who catches a bonito should record it by visiting jerseybiodiversitycentre.org.je or societe-jersiaise.org/sections/marine-biology.
