'They are homebirds and stay put' - 90pc of Sea bass return to Cork Harbour for summer
THERE’s no place like home for sea bass, with a new study showing that more than 90pc return to Cork Harbour after wintering in the Celtic Sea, and then confine themselves to an area of just 3kms.
Researchers led by NUI Galway have discovered that Cork-based fish, officially named Dicentrarchus labrax L., are “highly resident”, and remain within 3kms from where they were originally caught and tagged, a behaviour previously unknown.
Some 30 fish were caught and fitted with an electronic transmitter before being released back to the harbour. A series of listening posts dotted around the area identified individual fish when they swam within 500 metres of a listening post.
The study, published in ‘Scientific Reports’, was led and co-authored by Dr Tom Doyle from the Ryan Institute and MaREI Centre at NUI Galway with researchers from UCC’s MaREI Centre and expert angler, Jim Clohessy from Cork Harbour Angling Hub.
Dr Doyle said that the fish, which can live for up to 25 years and grow to 80cms in length, confined themselves to neighbourhoods within the harbour. Those living on the east of the harbour didn’t travel west, and vice versa,
“They would have been born in the Celtic sea somewhere, and it’s a lot to do with chance that they end up in Cork harbour,” he said. “They must imprint at some point in Cork Harbour and decide to call it home.
“We showed when you caught a fish, they really are localised. They are homebirds and stay put in this area over a number of months. Those tagged in the east of Cork Harbour came back to the east, and those tagged in the west went to the west.”
One fish in particular displayed this homing instinct.
“It basically went the wrong way and ended up on the east side (after returning after wintering). For two weeks it was moving up and down and didn’t seem to be settling anywhere, as if it wasn’t quite happy. Eventually, it just took a beeline to the westside where it found home and stayed there.”
Sea bass is found in Irish and UK waters and south into the Mediterranean and along North Africa. It cannot be caught commercially in Ireland, but is an important fish for recreational anglers who can catch one a day and is worth up to €70m a year to the economy.
Populations in northern European waters have been declining since 2010. The International Council for the Exploration of our Seas (ICES) has advised the EU Commission that there should be no catch of sea bass in 2017.