Sardines are up to two-thirds smaller now than they were 12 years ago as warming waters caused by climate change are killing the plankton they feed on.

Researchers at the French oceanographic institute, Ifremer, have been studying the sizes of sardines in the Mediterranean sea and the Bay of Biscay in the Atlantic.

While the former has seen the largest reduction in average sizes, the team report that Atlantic sardines have also lost around half of their weight around a decade ago.

The changing sardine populations are having knock on-effects, the team also noted, with other species like cod and seabird also suffering.

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Sardines are up to two-thirds smaller now than they were 12 years ago as warming waters caused by climate change are killing the plankton they feed on

Researchers from Ifremer have been studying the state of the sardines in the Mediterranean since 2008, after fishermen drew their attention to the shrinkage. 

In this time, Mediterranean sardines have shrunk from an average length of 5.1 inches (13 cm) to 3.9 inches (10 cm) last year, while their counterparts in the Bay of Biscay have gone from around 7.1 (18 cm) to 5.5 (14 cm).

The team’s analysis has ruled out predation, overfishing and disease as the cause of these changes in the sardine populations —with climate change the likely culprit.

‘For sardines and anchovies in the Bay of Biscay and in the Gulf of Lion [in the Mediterranean], we are leaning towards environmental factors linked to the rise in temperature and the fall in the quantity of food available,’ said biologist Clara Ulrich. 

Sardines feed off of microscopic plankton — a food source which has grown less wholesome with rising sea surface temperatures.

The problem is that the nutrients that feed the plankton are not rising from the cooler deep waters as they once did, the researchers explained.

Alongside reducing their size, the diminishing food stocks also appear to be curtailing the lifespans of the sardines, which has fallen from three years around a decade ago to just one year today.

Researchers at the French oceanographic institute, Ifremer, have been studying the sizes of sardines in the Mediterranean sea and the Bay of Biscay in the Atlantic

Researchers at the French oceanographic institute, Ifremer, have been studying the sizes of sardines in the Mediterranean sea and the Bay of Biscay in the Atlantic

‘It’s very alarming to see fish so damaged,’ Foundation of the Sea institute president Sabine Roux de Bézieux — who regards the newly-released findings as amounting to a crisis — told Europe 1 radio.

‘It’s a sign of the very bad health of the surrounding environment.’

‘This must alert us to the disaster which is playing out in the oceans because of climate change.’

'For sardines and anchovies in the Bay of Biscay and in the Gulf of Lion [in the Mediterranean], we are leaning towards environmental factors linked to the rise in temperature and the fall in the quantity of food available,' said biologist Clara Ulrich

‘For sardines and anchovies in the Bay of Biscay and in the Gulf of Lion [in the Mediterranean], we are leaning towards environmental factors linked to the rise in temperature and the fall in the quantity of food available,’ said biologist Clara Ulrich

Experts are also reporting that the shrinking sardines are have a knock-on effect further up their food chain, with their predators — seabirds in particular — no longer receiving the same levels of nourishment they used to enjoy.

The cascading shrinkage is not confirmed to the Mediterranean and the Atlantic, however — similar trends have been see in the Baltic Sea, the Indian Ocean and in the Pacific Ocean off of the coast of South America.

‘The Baltic cod have become so thin that they look like sardines,’ Ms Ulrich said. 

Meanwhile, off of the coast of the Galapagos Islands, Nazca booby birds have changed their diet preference over the last ten years from sardines to less nutrient-rich flying fish in response to the falling sardine numbers.

According to the researchers, the fish may have moved into cooler waters — and could therefore vanish completely from around the archipelago within the century if ocean temperatures continue to rise unabated.

Off of the coast of the Galapagos Islands, Nazca booby birds (pictured) have changed their diet preference over the last ten years from sardines to less nutrient-rich flying fish in response to the falling sardine numbers

Off of the coast of the Galapagos Islands, Nazca booby birds (pictured) have changed their diet preference over the last ten years from sardines to less nutrient-rich flying fish in response to the falling sardine numbers

According to the researchers, the fish around the Galapagos Islands may have moved into cooler waters — and could therefore vanish completely from around the archipelago within the century if ocean temperatures continue to rise unabated

According to the researchers, the fish around the Galapagos Islands may have moved into cooler waters — and could therefore vanish completely from around the archipelago within the century if ocean temperatures continue to rise unabated

There was some good news in the results of Ifremer’s latest survey, however.

Researchers have found that — following drastic restrictions imposed on the catch sizes of fishing boats — red tuna populations in both the Atlantic and the Mediterranean are once again growing healthily.

Despite this, around a quarter of the fish caught by French vessels belong to species which are presently threatened by overfishing — these include sardines in the Bay of Biscay, haddock in the Irish Sea and cod in the northeast Channel and the Irish sea. 

‘TIME IS RUNNING OUT’: DAVID ATTENBOROUGH’S WARNING TO HUMANITY

Sir David urged action against global warming and called it a man-made disaster that poses 'our greatest threat in thousands of years'

Sir David urged action against global warming and called it a man-made disaster that poses ‘our greatest threat in thousands of years’

Your excellencies, ladies and gentlemen.

‘We the peoples of the United Nations’.

These are the opening words of the UN Charter.

A charter that puts people at the centre.

A pledge to give every person in the world a voice on its future.

A promise to help protect the weakest and the strongest from war, famine and other man-made disasters.

Right now, we are facing a man-made disaster of global scale.

Our greatest threat in thousands of years. Climate Change.

If we don’t take action the collapse of our civilisations and the extinction of much of the natural world is on the horizon.

The United Nations provides a unique platform that can unite the whole world.

And as the Paris agreement proved, together we can make real change happen.

At this crucial moment, the United Nations has invited the world’s people to have their voice heard, by giving them a seat.

The People’s Seat; giving everyone the opportunity to join us here today, virtually, and speak directly to you the decision makers.

In the last two weeks, the world’s people have taken part in building this address, answering polls, sending video messages and voicing their opinions.

I am only here to represent the ‘Voice of the People’: to deliver our collective thoughts, concerns, ideas and suggestions.

This is our ‘We the peoples’ message. 

The world’s people have spoken. Their message is clear.

Time is running out.

They want you, the decision makers, to act now.

They are behind you, along with civil society represented here today. 

Supporting you in making tough decisions but also willing to make sacrifices in their daily lives.

To help make change happen, the UN is launching the Act Now bot.

Helping people to discover simple everyday actions that they can take, because they recognize that they too must play their part.

The People have spoken.

Leaders of the world, you must lead.

The continuation of our civilisations and the natural world upon which we depend, is in your hands.

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