Quote: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)