Large Australian fish stocks have declined by a third, a new decade-long study has revealed.
The study, looking at nearly 200 species at 544 sites, found the main cause of decline was overfishing, but climate change also contributed.
It compared areas where fishing was allowed to marine park areas where there was either limited fishing or no-take zones, and concluded that on fished reefs, the number of large fish declined by 36 per cent.
This was compared to 18 per cent in zones where there was limited fishing.
In no-take zones, stocks remained stable.
A single marine reserve can provide insurance against population decline for hundreds of species if well designed, the study by the University of Tasmania and University of Technology Sydney said.