Australia's fish populations are moving southward because the waters around Australia are becoming warmer, a new report says.

The "2012 Marine Climate Change in Australia Report Card" from Australia's national science agency, the Commonwealth Scientific and Industrial Research Organization, shows that climate change is having significant effects on Australia's marine ecosystems.

"Although there are some concerning findings in the 2012 report card, the information we've compiled is helping to ensure that ocean managers and policy makers are best placed to respond to the challenge of managing the impact that climate change is having on these systems," project leader Elvira Poloczanska of CSIRO said in a statement Friday.

While species now found in tropical and temperate waters are likely to move south, the report says, the researchers also found that some tropical fish species are better able to adjust to rising water temperatures than previously thought.

More than 80 Australian marine scientists from 34 universities and research organizations contributed to the report, led by CSIRO. It is the second such report card since 2009.

"Australia has some of the world's most unique marine ecosystems," Poloczanska said.

"They are enjoyed recreationally, generate considerable economic wealth through fisheries, aquaculture, and tourism, and provide irreplaceable services including coastal defense, oxygen production, nutrient recycling and climate regulation."

Climate change is also resulting in a decline in some temperate fish stocks and ocean acidification is beginning to affect shellfish, the study indicates.

Separately, research also led by CSIRO and published in Nature this week, says that South Pacific island nations will face almost twice as many droughts, floods and extreme tropical cyclones over the next 80 years because of climate change.

The study attributes the expected changes to the reaction to greenhouse warming by the South Pacific rain band, which spans the Pacific from below the equator south-east to French Polynesia. The band's location determines rainfall levels and the frequency of cyclones in the South Pacific.

"Understanding changes in the frequency of these events as the climate changes proceed is therefore of broad scientific and socio-economic interest," said CSIRO oceanographer Wenju Cai who led the study.

The researchers said that while the rain band shifted northward toward the equator about once every 11 years from 1891-1990, the frequency is now once every seven years.

That means there will be more natural disasters in affected areas, the researchers say.

"A central issue for community adaptation in Australia and across the Pacific is understanding how the warming atmosphere and oceans will influence the intensity and frequency of extreme events," a CSIRO release stated. "The impact associated with the observed extreme excursions includes massive droughts, severe food shortage and coral reef mortality through thermally induced coral bleaching across the South Pacific."

Countries, such as Vanuatu, Samoa, and the southern Cook Islands, in the rain bands' average position can be expected to see forest fires and droughts as well as increased frequency of tropical cyclones, whereas countries to which the rain band moves may experience extreme floods, the release said.