Fish and chips could be off the menu as global warming threatens to wipe out cod and haddock stocks, study warns
- Rising temperatures reduce oxygen in the oceans, which makes fish smaller
- Over last 50 years, oxygen in oceans has already reduced two to five per cent
- Larger marine species, such as cod and haddock, could shrink or go extinct
Fish and chips could be off the menu permanently due to global warming, a study has warned.
Scientists say larger marine species – including cod and haddock – face being wiped out as rising temperatures reduce oxygen in the oceans.
The findings were based on an analysis of different sized crustaceans found in abundance in the Antarctic.
When the gas in the water they were in was cut they got smaller – supporting the theory bigger sea creatures are more vulnerable to climate change.
Previous studies have suggested portions of the British pub classic will be up to a fifth smaller by 2050.
Rising sea temperatures has reduced the amount of oxygen in the oceans, which means larger marine species could shrink in size or go extinct (file photo)
Study coauthor Dr Simon Morley, an ecophysiologist with the British Antarctic Survey, said: ‘Marine animals thrive in the Southern Ocean but life in these freezing waters has led to the evolution of many distinct characteristics.
What are the threats facing cod and haddock?
Overfishing has decimated cod and haddock stocks a number of times. Most recently, haddock from three North Sea and west of Scotland fisheries were removed from sustainable seafood lists because stocks had fallen below acceptable levels in 2017. During the 1990s, Newfoundland in Canada was forced to ban cod fishing because stocks were nearly wiped out.
While rising sea temperatures reduces the size of cod and haddock, it also forces the fish further north in search of cooler waters. Other fish not traditionally found in UK waters will appear more frequently too – with mixed consequences. For example, cuttlefish and sardines are being caught in increasing numbers, but researchers have warned slipper limpets could ruin oyster and mussel beds.
‘These “strategies”, which allow animals to survive in the cold, are expected to make many Antarctic marine invertebrates and fish vulnerable to the impact of climate change.
‘Understanding these impacts will not only help us to predict the fate of marine biodiversity at the poles but will also teach us much about the mechanisms that will determine the survival of species across the world’s oceans.’
The study suggests failure to control greenhouse gas emissions will have a greater impact on marine ecosystems than previously feared.
Co-author Professor John Spicer, a marine zoologist at the University of Plymouth, has spent more than 30 years examining the effect of climate change on ocean organisms.
He said: ‘Over the last 50 years, the oxygen in our oceans has decreased by around two to five per cent and this is already having an effect on species’ ability to function.
‘Unless they adapt, many larger marine invertebrates will either shrink in size or face extinction, which would have a profoundly negative impact on the ecosystems of which they are a part. This is obviously a major cause for concern.’
Over the past 50 years, the oxygen in our oceans has already decreased by around two to five per cent. Previous studies have suggested portions of cod or haddock could shrink by up to a fifth by 2050 (file photo)
Professor Spicer said it was one of the most important changes occurring in an ocean becoming increasingly modified by human activities – making the water warmer.
The gigantic animals of polar waters exist because more oxygen dissolves there than in the warmer seas of temperate and tropical regions.
As our ocean warms and oxygen decreases, it has been claimed this will have a greater impact on large marine invertebrates and fish.
Professor Spicer and Professor Morley looked at four types of crustacean, known as amphipods, abundant off coast of the western Antarctic Peninsula.
They are named Paraceradocus miersi, Shraderia gracilis, Probulisca ovata and Prostebbingia brevicornis.
Interestingly, the study also identified ‘evolutionary innovation’ – such as the presence of special pigments in their body fluids to boost the transport of oxygen.
These can help offset any respiratory disadvantages of large body size, explained Professor Spicer.
He added: ‘Our research also shows some species have evolved mechanisms to compensate for reductions in oxygen, and so it is not always as simple as drawing a link between size and future survival.
‘But it would be foolhardy to pin our hopes on such “evolutionary rescue”. Many large species will almost certainly be the first casualties of our warming, oxygen-poor ocean.’
The full findings of the study were published in the journal Philosophical Transactions of the Royal Society B.