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Anchovies, herring and pilchard could face extinction due to warming waters – study

By Nina Massey, PA Science Correspondent

Commonly eaten fish including anchovies, herring and pilchard could face extinction as warming oceans increase pressure on their survival and hamper their ability to adapt, new research suggests.

The study indicates that the fish will struggle to keep pace with accelerating climate change as warmer waters reduce their size, and therefore their ability to relocate to more suitable environments

Researchers say the study is the first to counter the scientific theory that decreased movement will result in more species, by suggesting the opposite is true.

This suggests many species will also be less able to evolve to cope with warmer temperatures, increasing their risk of dying out.

Professor Chris Venditti, an evolutionary biologist at the University of Reading, and co-author of the study, said: “Warming waters are a double whammy for fish, as they not only cause them to evolve to a smaller size, but also reduce their ability to move to more suitable environments.”

He added: “Our research supports the theory that fish will get smaller as oceans warm under climate change, but reveals the worrying news that they will also not be able to evolve to cope as efficiently as first thought.

“With sea temperatures rising faster than ever, fish will very quickly get left behind in evolutionary terms and struggle to survive.

“This has serious implications for all fish and our food security, as many of the species we eat could become increasingly scarce or even non-existent in decades to come.”

The study published in Nature Climate Change comes as a report from the UN’s Intergovernmental Panel on Climate Change warned the world will reach or exceed temperature rises of 1.5C – a limit countries have pledged to try to keep to in order to avoid the most dangerous consequences of warming – over the next two decades.

The new research, led by the Centre for Advanced Studies in Arid Zones (CEAZA) in Chile and the University of Reading in the UK, used statistical analyses of a large dataset of globally distributed fish species to study their evolution over 150 million years.

Scientists suggest it provides the first solid evidence of how historical global temperature fluctuations have affected the evolution of these species.

The study focused on Clupeiformes – highly diverse fish found all over the world. This group includes important species for fisheries, such as anchovies, Atlantic herring, Japanese pilchard, Pacific herring, and South American pilchard.

But the researchers say the findings have implications for all fish.

Until now, fish have only had to deal with a maximum average ocean temperature rise of around 0.8C per millennium.

This is far lower than warming rates reported by the National Oceanic and Atmospheric Administration of 0.18C per decade since 1981.

The findings support the expectation among scientists that fish will generally get smaller and move less as the world warms.

This is due to having to increase their metabolism and therefore needing more oxygen to sustain their body functions.

Researchers suggest this will have an impact on fish species as larger fish are able to travel longer distances owing to their greater energy reserves. Smaller fish are less able to seek out new environments with favourable conditions as the climate changes.

The findings contradict the assumption that an increase in smaller fish will see more new species emerging because of concentrating genetic variations within local areas.

Instead, the scientists found warmer waters would lead to fewer new species developing, robbing fish of another of key weapon to cope with climate change.

Overfishing has also been linked to fish smaller in size, so the new study adds to the list of pressures they face as a consequence of human actions.

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