Scientists and the Marine Stewardship Council (MSC) have warned that this year’s heatwave in the North Atlantic could be disastrous for fish stocks that people depend on for food and livelihoods.
The ocean surface temperature has risen above the previous record since early March with a rise of up to 5 degrees Celsius above the long-term average, and the US National Oceanic and Atmospheric Administration has classified it as “beyond extreme” – the highest category.
Human-induced climate change is further warming the oceans, which have absorbed 90% of the excess heat generated by greenhouse gas emissions.
Meanwhile, scientists said natural events such as changes in wind patterns have pushed the temperature of the North Atlantic Ocean to record levels.
El Niño, a naturally occurring warming phenomenon in the eastern tropical Pacific Ocean, has also had an impact, raising average ocean and air temperatures worldwide, but its effects are not thought to be related to the North Atlantic heatwave.
Experts say climate change is shifting the temperature baseline, making heat waves more frequent and more extreme and potentially as devastating to some marine life as those on land.
Dr Christopher Frye of the Marine Institute at the University of California, Santa Barbara, said: “In the past decade, marine heatwaves have disrupted fisheries around the world.
“If conditions in the North Atlantic remain hot, similar disasters could loom.”
Fish in the ocean, sandwiched between the east coast of North America, the UK and western Europe, depend on cold waters to breed, with one species – the spring spawning Norwegian herring – down 40% since 2009, which is thought to be due to warming oceans.
MCS is concerned that a combination of warming oceans and poor international governance could lead to a collapse in fish stocks that would put thousands of people out of work.
Dr Olaf Sigurd Kjespo, from Norway’s Institute of Marine Research, said: “We know that marine fish stocks are sensitive to changes in temperature.
We have already seen that climate affects their distribution, their ability to reproduce and their mortality rates.
Rapid warming of the seas could accelerate these changes. It could also have a significant impact on the ability of herring and blue whiting to reproduce based on recent analyses.”
Many species are moving north towards the North Pole, replacing native species there in a process known as atlantification, said Professor Geraint Tarling, an oceanobiologist with the British Antarctic Survey.
Dr Craig Donlon, head of the Earth’s Surfaces and Interiors division at the European Space Agency, described the warming of the North Atlantic this year as a “frightening situation” but added that the ecosystem would adapt, with species migrating north being replaced by others arriving from the south.
He said: “We can expect to see changes in the structure of neighborhoods, and the ecosystem will adapt.
“Some species will migrate north to the waters they feel most comfortable in, temperature-wise, and of course, other species will migrate north to our waters from the south, which brings more diversity.”
Last week the UK government announced plans to start a large-scale monitoring program for surface trawlers over 24 metres, with cameras and GPS to record the size and types of catches in English waters in a bid to manage stocks more sustainably.
Irene Bridle, Regional Director for Europe at MSC, said: “Policy makers must find a way to incorporate stock shift changes, such as changing pelagic distributions in the Northeast Atlantic, into long-term and robust fisheries management plans.
“Without joint and effective planning, our fisheries resources could be at risk of overexploitation, overfishing and even stock collapse.”