Sydney - Sharks are being driven towards beaches by extraordinary rises in ocean temperatures, fish experts said on Sunday.

The West Australian Department of Fisheries is investigating whether a marine heatwave, in which areas of ocean water reached 30 degrees Celsius in the last few years, caused fish stocks in those regions to almost disappear. This would have driven predators like sharks closer in to shore because fish collect in cooler waters.

Five people have been killed in shark attacks at western Australian beaches in the past two years and there have been far more sightings of large shark packs near to shore.

“It may be the sharks are coming in with the colder water or it may be that the things they're feeding on are coming in with the colder water and the sharks are following them,” Fisheries director general Stuart Smith told the West Australian newspaper.

Smith said the rise in ocean temperatures in some areas to as much as five degrees above normal was at first considered an aberration, but it is now believed to be part of a broader environmental change.

Rising water temperatures have devastated the region's rock lobster industry. - Sapa-dpa