Too hot to handle? Ocean warming pushes Atlantic tuna north

A new study warns that ocean warming is impacting giant Atlantic bluefin tuna migrations, which could impact their annual visits to Ireland in the future.

A new Irish-led study suggests tuna are migrating further north each year as a result of the climate crisis, which could have significant consequences for Ireland in the future.

The study looked at giant Atlantic bluefin tuna, which are normally seasonal visitors to Ireland during the summer and autumn months. These fish swim thousands of kilometres every year for their annual migrations.

But the research suggests these fish are migrating further north to higher latitudes each year. Grace McNicholas, a PhD candidate at Trinity College Dublin and lead author of the study, said the team believes this is due to “warming seas”.

“Understanding how climate change may alter the conditions they encounter along their journey is really important as it helps us to predict future migration routes and ultimately guide management decisions for this ecologically and economically important species,” McNicholas said.

This particular tuna species had a global population crash in the past, but has been reestablishing itself in feeding grounds across Ireland – but this may be threatened by warming oceans in the future, the researchers warn.

To assess the issue, the Irish Marine Institute worked with Irish anglers to put satellite tags on more than 50 tuna, which allowed researchers to track their route for up to 12 months once they left Irish waters.

The team then modelled the oceanographic conditions experienced by the tagged tuna, to better understand their preferred marine habitats. The results suggest that the fish moved to more northerly seas as the temperatures increased.

“This study is yet another clear example of the massive impact climate change is having on marine habitats,” said Trinity assistant professor Dr Nick Payne, one of the study’s co-authors. “Atlantic bluefin are a hugely important species for lots of reasons, and it’s looking like they might move further north in the near future. This could have significant impact on various coastal communities, including some of those in Ireland.”

There were several marine heatwaves reported last year, with the average sea surface temperature for the European ocean being the warmest on record. In June, the marine heatwave in the Atlantic Ocean around Ireland and the UK was classified as “extreme” and even “beyond extreme” in some areas, with temperatures as high as 5 degrees Celsius above average.

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