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Climate in uncharted waters as hundreds of millions of anchovies and sardines arrive off Irish coast


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Last year was the warmest in the past 100,000 years – and it’s getting warmer

The Irish Marine Institute survey shows levels of anchovy schools have increased fivefold in the Celtic Sea in the last three years.

The scientific expedition to gauge levels of the traditional species of herring in the waters off Ireland’s south coast by RV Tom Crean last autumn used sound waves to identify the size of fish schools under the surface.

The Celtic Sea Herring Acoustic Survey (CSHAS) 2023 estimated that over 769 million individual anchovies were swimming under the surface compared to over 143 million in 2020, and over 93 million in 2011.

“This is a dramatic increase. They are phenomenal numbers,” said marine biologist Kevin Flannery, the director of Dingle Oceanworld.

Marine biologist Dr Kevin Flannery from Dingle Oceanworld. Photo: Domnick Walsh

“The fishermen working on the ground believe the levels are even higher. They are finding them in such numbers that some fishermen discovered them in shrimp pots.

“It’s obviously global warming. There is a northward movement of all species.

“What the Irish people were eating on the beaches of Portugal and Spain are now off the coast of Cork, Kerry and Waterford. A major fishery for this species has been developed off Cornwall, and we need to do the same.”

Today’s News in 90 Seconds – April 23rd

The survey also estimated that the same expedition recorded 767 million individual sardines, another species usually found in this abundance in more southern waters.

A spokesperson for the Irish Marine Institute said anchovies and sardines are small, relatively short-lived, pelagic species well known for boom and bust fluctuations in abundance.

“While the abundance of anchovy and sardine observed on the CSHAS 2023 was the highest in the survey’s time-series, both these species have been found in the Celtic Sea at varying abundances over a longer time frame.”

They said the long-term trends discussed in a recent climate report concluded there is evidence of increases in warm-water species to the south of Ireland this century, with an increased abundance of European anchovy noted in both scientific surveys and commercial catches.

Ireland experienced a marine heatwave off the Kerry coast which saw temperatures rise four or five degrees

At present, the current world sea-surface temperature is 21.1C, compared to 21C at this time last year, and 20C in April 1985. Off Irish shores, this month’s sea temperatures range from 10C to 10.6C, and this is about 0.5C higher than historic averages.

The ocean heatwaves are colliding with the warmest conditions ever observed on land, with data from the Copernicus Climate Change Service showing the Earth’s average temperature last year was 1.48C hotter than the preindustrial average. But the warming seas are causing even more concern as it takes more energy to heat the ocean than the air.

Last summer, Ireland experienced a marine heatwave off the Kerry coast which saw temperatures rise four or five degrees.

Gavin Schmidt, director of the Nasa Goddard Institute for Space Studies, saw sea-surface temperatures in the North Atlantic begin to shoot up, starting last March. Schmidt, one of the world’s leading climate experts, said last week he was not surprised to see last summer’s marine heatwaves off the coast of Kerry.

“I’m not at all surprised. As for the causes… there are lots of possible causes, all of which may be playing a role,” he said.

“There are the greenhouse gas-driven long-term trends of course, but also wind patterns, the North Atlantic oscillations, Saharan dust or the lack of it…

“I haven’t yet seen any reasonable synthesis of all this that would allow us to attribute recent changes to any of these with any confidence.

“If this is a ‘blip’ — a combination of many unlikely co-incidents — it will fade, but if it’s the impact of something systematic, then it will have more persistence.

“Right now, there is a lot of work going on to examine this, but no answers as yet.”

Writing a column in the journal Nature, the climatologist said climate models cannot explain 2023’s huge heat anomaly.

“If the anomaly does not stabilise by August — a reasonable expectation based on previous El Nino events — then the world will be in uncharted territory.

“We need answers for why 2023 turned out to be the warmest year in possibly the past 100,000 years. And we need them quickly.”

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