Dozens of dead fish, including threatened species, have washed ashore local Australian beaches, all attributed to a massive toxic algae bloom.

An Australian state has closed two beaches after surfers reported feeling unwell while dead fish and unusual foam washed ashore.

But the March 15 trip, eight kilometres off the coast of Batemans Bay on the NSW south coast, would become what the Canberra man called the worst day of fishing of his life. "When we stopped we [had] a million of these fish swarm the back of the boat,