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.
Asteroids have broken apart many times over the eons, but never before have scientists been able to witness it.
Should these ships become a reality, a total of 44% of expenses could be cut from operating cargo ships, according to industry consultant Moore Stephens LLP.
Earthuquake lights sometimes appear in the sky before an earthquake takes place and are often mistaken for UFOs.
Remains of the new species were unearthed in Portugal by an amateur fossil hunter in 2003 in the rock cliffs of Lourinhã
The females of an Asian swallowtail butterfly species known as the Common Mormon often mimic the appearance of another species of butterfly that is toxic for predators to eat
Scientists from Turkey designed 'the smart infrared cameras' to deal with dense fog related flight delays which cause thousands of flights to be postponed or cancelled each year.
Artificial muscles can bear 117 times more than natural muscles.
Scientific works by students aged between 11 and 15 in invention and design categories will take part in the olympiad.
GCHQ collected images from the webcam chats of more than 1.8 million users globally in a six-month period in 2008 alone
NASA'a Kelper telescope has discovered 715 new planets outside of our solar system.
The vault, which was designed to withstand all disasters, was opened in 2008 in order to store an adequate amount of seeds which would enable the human species to revive lost crops in the event of global disaster.
A cybersecurity firm said that it uncovered stolen credentials from some 360 million accounts that are available for sale on cyber black markets
NASA says about 100 tons of material from space enter Earth's atmosphere every day. The moon, with no protective atmosphere, is fair game for celestial pot-shots
"When or if the NSA blurs the line between its defensive and intelligence-gathering roles and exploits a position of trust, that's a problem," head of security pioneer RSA said
Co-founder of WhatsApp announces that telephone calls can be made via WhatsApp.
In the past, artificial muscles have been crafted out of materials including metal wires and carbon nanotubes, but they have proven to be costly to make and tricky to control.