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.
Apple denied creating any “back doors” for intelligence agencies.
The fetuses’ heart rates were monitored at 32, 33 and 34 weeks as they listened to a recording of a female stranger recite the rhyme.
On July 23, 2012, the Sun experienced the most powerful in 150 years, NASA revealed on Wednesday.
Tech giant Apple reported Tuesday a 6 percent increase to $37.4 billion in quarterly revenue after selling 35.2 million iPhones.
The total number of online access devices projected to rise to 50 billion in 2020 and 100 billion in 2030.
Tasmania is currently the only Australian state that bans genetically modified food crops and animal feed.
U.S. Magistrate Judge Gabriel Gorenstein said Friday he had authorized a warrant to be served on Google Inc for the emails of an unnamed individual who is the target of a money laundering investigation.
The freighter was loaded with more than 3,660 pounds (1,660 kg) of food, science equipment and supplies for the space station, a $100 billion research laboratory
The remains include two Tyrannosaurus bataar skeletons, a fossilized egg and a well-preserved 'nest' of several Oviraptor skeletons.
The MindRDR software monitors high levels of concentration, allowing users to take photographs and post it online without even having to move.
Angara rockets are a key to President Vladimir Putin's effort to reform a once-pioneering space industry hobbled after years of budget cuts and a brain drain in the 1990s.
It is hoped that by 2040 drones will be able to use 3D printers to print out mini-drones and repair themselves.
Russian Presidnt Vladimir Putin denied he was restricting web freedoms, saying his main concern was protecting children from indecent content.
Producing stem cells has become fast, easy, and inexpensive.
It's believed that a collision of two asteroids out in space caused a shower of meteors to rain down on Earth during the Ordovician Period some 470 million years ago.
Scientists discovered that wild chimps communicate 19 specific messages to one another with a “lexicon” of 66 gestures.