North Sea fish hit hardest by climate change
March 22nd 2019
The surprise discovery this month that climate change has decimated key North Sea fish populations means fishing quotas must be reconfigured to take account of global warming, experts say. A groundbreaking study has found that the North Sea is being hit much harder by climate change than any other major fishery in the world. It found that seven major North Sea species, including cod and haddock, have collectively tumbled by 34.6 per cent since 1930, soley as a result of ocean warming. When other factors such as overfishing are included the over declines are much higher still.
Role of climate change largely unnoticed
But while the crisis facing our seas has been long been blamed on overfishing, climate-change induced ocean warming has been playing a considerable – but largely-unnoticed – role in declining fish populations, the study finds.
This discovery suggests that, even if quotas were strict and successfully enforced, fish stocks face the threat of further major declines in the future as the oceans continue to warm. As such, the institutions responsible for setting quotas – which in the case of UK fishing waters is the EU – should explicitly factor in the impact of climate change in their calculations, according to environmental law firm ClientEarth.
“We are alarmed by reports that climate change is impacting North Sea fish stocks and particularly concerned about the additional strain this puts on vulnerable stocks that are already struggling due to overfishing,” said Jennifer Reeves, fisheries lawyer at environmental law firm ClientEarth. “EU decision-makers must start considering how climate change will impact fish stocks when setting quotas and fisheries management policies,” she said.
Non-fishing factors like climate change need to be taken into account when deciding how much fishing can take place, to ensure the overall cumulative impact is not unsustainable. Otherwise at some point quotas will no longer reflect the reality of species distribution across the EU, she said.
After Brexit
If the UK leaves the EU with no deal, responsibility for quotas would switch to the UK government whereas if it leaves with a deal it is likely the UK would be subject to EU quotas for at least two years, experts say.
Chris Free, the University of California Santa Barbara researcher who led the study, is calling on fisheries managers all over the world to “account for climate change” in their management decisions. His research, conducted while he was at Rutgers university, separated out the effects of warming water from overfishing and other factors.
It found that North Sea fish stocks declined by almost twice the level seen on the Iberian Coast, the next biggest casualty of climate change of the world’s fisheries – which saw stocks decline by 19.2 per cent between 1930 and 2010.
Major fish stocks suffer
Over that period, the volume of cod, haddock, whiting, herring that can be sustainably fished in the North Sea every year has fallen by about a quarter as the warming water kills off huge volumes of plankton, the tiny organisms that lie at the base of the marine food chain, the study found. This has drastically reduced food supplies for fish – some of which eat the plankton and others which eat other marine organisms that rely on them for their food.
The North Sea has been hit particularly hard because, due to the quirks of global warming, temperature rises are distributed unevenly around the globe – and the North Sea has risen considerably more than most other seas. It has increased by 0.8C from an average of 9.8C in 1930 to 10.6C in 2010.
Sandeels also being hit
North Sea Sandeels are also suffering, with climate change dragging down populations by around 30 per cent over the period.
Euan Dunn, the RSPB’s Principal Policy Officer said, “There is now compelling scientific evidence that rising sea temperatures are reducing the abundance of sandeels on which so many of our seabird species rely to feed themselves and raise young. This is likely to be a key reason behind the major recent declines in seabird populations such as the kittiwake and puffin.”
The 34.6 per cent decline in fish stocks recorded in the North Sea as a result of climate change compared to a 5.3 per cent drop in the South Atlantic Ocean and a 4.7 per cent drop in the North Atlantic Ocean. Only the tiny Sea of Japan, situated within the Japanese archipelago, was higher, at 34.7 per cent
Overall, fish stocks around the world fell by 4.1 per cent between 1910 and 2010 as a result of ocean warming, according to the first study to comprehensively quantify the effect of climate change on fish stocks worldwide.
Experts say the study is groundbreaking because it finds the effects of climate change are already upon us.
“We were stunned to find that fish around the world have already responded to ocean warming. These aren’t hypothetical changes sometime in the future,” said Malin Pinsky, of Rutgers’ University.
The study
The research examined 235 fish populations made up of 124 species in 38 regions of the world. It used a standard measure of fish stocks calculated by determining the number that could be sustainably fished each year if the fishery was perfectly managed – meaning no overfishing, no disease, oil spills or other negative factors.
Known as the maximum sustainable yield (MSY), any changes in this level is soley governed by ocean warming.
In reality, despite widespread efforts to use quotas to put a lid on it, overfishing does occur – putting further pressure on fish populations, many of which are already under siege from climate change.
A fisherman’s tale:
Graham Doswell, a small-boat fisherman based in Eastbourne, has definitely noticed a change in fish distribution in his decades as a fisherman in the English channel and thinks global warming is likely to be a major factor.
“There are lots of difference, for sure. Three or four years ago there was tons and tons of cod in channel and this year its been very scarce, almost non existant,” he said. “Meanwhile, the herring are changing their patterns. They come out of the North Sea and round into the channel – but they seems to be a month later than it used to be,” Mr Doswell added.
Bass moved into North Sea
“The bass have moved further up into the North Sea – whereas you didn’t use to catch bass in the north sea.”
Mr Doswell said there is no doubt that the sea is getting warmer. “When I was fishing with my father, we used to measure the water temperature – and in the winter used to be far, far cooler than it is now,” said Mr Doswell, whose boat is 9.8 metres long – classing it as small.
“I am concerned about global warming. Being a small boat fisherman, we haven’t got the capacity to say ‘Oh the fish have moved up into the North Sea, we can follow them round’. We’re stuck with what we’ve got here and if it carries on changing it could be a problem,” he said.
How North Sea compares to others
To put the climate change effect into perspective, the North Sea haddock population fell by 59.9 per cent overall between 1990 and 2010 as a result of overfishing and other factors – as well as ocean warming. North Sea Whiting declined by 39.8 per cent, cod by 39.2 per cent and sole by 38.9 per cent over the same period.
“Overfishing provides a one-two punch to fisheries facing warming waters. It not only makes fisheries more vulnerable to ocean warming, but continued warming will also hinder efforts to rebuild overfished populations,” said Dr Free.
Debbie Crockard, senior fisheries policy advocate at the Marine Conservation Society, said: “The combination of climate change and overfishing is problematic as the cumulative impacts are often much more severe than individual ones.”
The oceans that have benefitted from global warming
While most fish species in most seas are suffering from ocean warming some are benefitting. The Mediterranean Sea and the Norwegian Sea, saw increases of 0.6 per cent and 1.1 per cent, in major fish stocks respectively, between 1930 and 2010, as they benefitted from warming waters. Meanwhile, the South Pacific saw a 4.2 per cent rise and the Baltic Sea an 11.2 per cent jump.
The winning fish
Likewise, while some fish are suffering at the hands of global warming, others were flourishing. The Greenland Halibut, living in the Gulf of St Lawrence between the US and Canada, for example, have seen their stocks rise by 53.6 per cent in 80 years as a result of climate change.
In the same waters, the Atlantic Cod is up by 45.9 per cent while the Atlantic Herring of the Bothnian Sea, between Sweden and Finland, have increased by 30.6 per cent.
Experts suggested any benefits due to climate change could be relatively short lived, however. “Fish populations can only tolerate so much warming. Many of the species that have benefited from warming so far are likely to start declining as temperatures continue to rise,” said Olaf Jensen, also of Rutgers.
How global warming is decimating some fish populations and helping others
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