BEIJING, April 27 (Xinhuanet) -- Fish living in
warmer, shallow waters are growing faster and fish growing in deep ocean waters
are growing slower, according to an Australian study. Why? Climate change.
The research by Australia's Commonwealth Scientific
and Industrial Research Organisation (CSIRO) found fish were growing faster in
waters above a depth of 250 meters (825 feet) and had slower growth rates below
1,000 meters (3,300 feet).
"These observations suggest that global climate
change has enhanced some elements of productivity of shallow-water stocks but at
the same time reduced the productivity and possibly the resilience of deep-water
stocks," said CSIRO oceanographer Ron Thresher.
"Growth rates in the deep-water fish are slowing
because water temperatures down there have been falling, apparently for the last
several hundred years," Thresher told Reuters on Friday.
"Fish growth rates are closely tied with water
temperatures, so warming surface waters mean the shallow-water fish are growing
more quickly, while the deep water fish are growing more slowly than they were a
century ago."
Populations of large marine species are subject to
two major stress factors, commercial fishing and climate change, and the heavy
exploitation increases the sensitivity of species to environmental effects, said
Thresher.
Thresher's team studied 555 fish specimens, such as
Banded Morwong, Redfish, Jackass Morwong and Orange Roughy, from waters around
Maria Island off the east coast of Australia's island state of Tasmania. The
fish were aged 2 to 128 years and had been born between 1861 to 1993.
Changes in sea temperature were obtained from a
60-year-long record at Maria Island and by using 400-year-old deep-ocean corals
to measure temperature at depth.
The study found sea temperatures off east Tasmania
had risen nearly two degrees Celsius, while a southerly shift in South Pacific
winds had strengthened the warm, southerly flowing East Australian Current which
runs down Australia's east coast.
(Agencies)
Print
