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.
AG600 developed for use in emergency operations has max cruising speed of 500 km per hour, max flight range of 4,500 km
Vast quantities of rare gas hint at Earth’s past, could power planet’s future
Global temperatures at record highs; Arctic sea ice levels at record lows
23-year-old researcher to create computer models of brain structures in world's largest particle physics laboratory
New mobile game already used by 5 percent of Android users in US
The $180m radio telescope with size of 30 football fields is expected to be operational by September, state media says.
The 41st Committee on Space Research (COSPAR) Scientific Assembly will take place between July 30 and August 7 at the Istanbul Congress Center
India launches largest successful satellite mission as it continues focus on space reseach
Court-ordered payout comes on same day company pulls fake refugee rescue app
Driverless minibus called Olli, capable of carrying up to 12 people, released by IBM and Local Motors
Popular social media network Twitter has broken, with the network's website and mobile apps inaccessible for users worldwide
In April, Germany officially announced a new incentive and investment program to accelerate the adoption of electric cars in the country.
Findings based on laser technology challenge previous theories on urban, water systems around temple complexes
With clean energy, ‘you can reconcile ecology and economy’, says Solar Impulse navigator