Woırld Bulletin / News Desk
Fish are likely to get smaller on average by 2050 because global warming will cut the amount of oxygen in the oceans in a shift that may also mean dwindling catches, according to a study on Sunday.
Average maximum body weights for 600 types of marine fish, such as cod, plaice, halibut and flounder, would contract by 14-24 percent by 2050 from 2000 under a scenario of a quick rise in greenhouse gas emissions, it said.
"The reductions in body size will affect whole ecosystems," lead author William Cheung of the University of British Columbia in Canada, told Reuters of the findings in the journal Nature Climate Change.
His team of scientists said a trend towards smaller sizes was "expected to have large implications" for ocean food webs and for human "fisheries and global protein supply."
"The consequences of failing to curtail greenhouse gas emissions on marine ecosystems are likely to be larger than previously indicated," the U.S. and Canada-based scientists wrote.
They said global warming, blamed on human burning of fossil fuels, will make life harder for fish in the oceans largely because warmer water can hold less dissolved oxygen, vital for respiration and growth.
"As the fish grow bigger and bigger it will be difficult to get enough oxygen for growth. There is more demand for oxygen as the body grows. At some point the fish will stop growing," Cheung said of the study, based on computer models.
As water gets warmer, it also gets lighter, limiting the mixing of oxygen from the surface layers towards the colder, denser layers where many fish live. Rising water temperatures would also add stresses to the metabolic rates of fish.
The scientists said fish stocks were likely to shift from the tropics towards cooler seas to the north and south.
Average maximum sizes of fish in the Indian Ocean were likely to shrink most, by 24 percent, followed by a decline of 20 percent in the Atlantic and 14 percent in the Pacific. The Indian Ocean has most tropical waters of the three.
The study said a computer model projected that ranges for most fish populations would shift towards the poles at a median rate of 27.5 km to 36.4 km (17.1-22.6 miles) a decade from 2000 to 2050.
Adding to climate change, other human factors "such as over-fishing and pollution, are likely to further exacerbate such impacts," they wrote.
Cheung said the shrinking of fish would have big but unknown effects on marine food chains. Predator fish like cod that swallow prey whole would become less fearsome, perhaps allowing smaller species to thrive.
"Cod ... can only eat fish that can fit into their mouth. They are not like lions or tigers" that can attack animals that are larger than they are, he said.
The climate scenario used in the study would mean an increase in world temperatures of between 2 and 5.4 degrees Celsius (3.6 to 9.7 Fahrenheit) by 2100, the second biggest gain of six scenarios used by the U.N. panel of climate experts.
"The results will be quite similar," using other scenarios, Cheung said.
Facebook will appeal a date privacy ruling in Belgium that forces the social media giant to stop collecting digital information about people who are non-members
Japanese, Chinese, Irish scientists win 2015 Nobel prize in medicine for malaria and parasite research
Discovery could have major implications for pursuit of life on the red planet
Lawsuit sheds light on no poaching policy at Silicon Valley’s biggest companies
Searches for oncoming storms will display information such as maps, forecasts, reminders and preparedness instructions
New service unveiled as survey finds Americans having hard time navigating smartphone etiquette
Turkcell, Vodafone and Avea bid total of over €1.14 billion for the right to use frequencies on the new network
Petition 'will present at least two substantial questions concerning design-patent liability and damages'
The Istanbul Electric Tram and Tunnel Company plans to launch one solar-powered bus on Thursday and several more in the coming days
Roughly 70 million tonnes of fibres are traded globally per year, but nearly two thirds are made from non-renewable products like petroleum and natural gas.
Researchers havfe said that the flaw leaves data stored by apps vulnerable with almost every category of app considered vulnerable
SpaceX revealed Monday that it is building a test track for the Hyperloop, a concept for ultra-fast ground transport the company’s CEO, Elon Musk, unveiled.
Biologists have created chicken embryos with dinosaur-like faces by tinkering with the molecules that build the birds' beaks.
Product available for pre-order in nine countries but devices won’t ship for weeks.
Nobel Prize-winning scientists' discovery can be manufactured cheaper thanks to Nanografi process.
Most industry experts expect the first product of 5G technology in the run-up to the Tokyo Olympics in 2020.