Optimism is rising among scientists that parts of the Great Barrier Reef that were severely bleached over the past two years are making a recovery.

Scientists from the Australian Institute of Marine Science this month surveyed 14 coral reefs between Cairns and Townsville to see how they fared after being bleached.

The institute's Neil Cantin said they were surprised to find the coral had already started to reproduce.

Coral which has produced eggs near Fitzroy Island, in Queensland ( Supplied: Australian Institute of Marine Science, Neal Cantin )

"We're finding corals that are showing early signs of reproductive development, really visible eggs that we can see under the naked eye," Dr Cantin said.

"[It's] very surprising as previous studies have shown a two-to-three year delay in reproductive activity following bleaching events.

"It means they have enough energy, they've recovered the zooxanthellae and the symbiosis and they even have energy to invest in reproduction and egg development."

Nearly two thirds of the Great Barrier Reef was affected by bleaching in 2016 and 2017, killing up to 50 per cent of coral in those parts.

Sorry, this video has expired Severe coral bleaching hits two-thirds of Great Barrier Reef

Dr Cantin said scientists found eggs at most of the reefs in the Cairns region, including at Arlington Reef and Fitzroy Island.

"What it means is the corals along the entire Great Barrier Reef, are survivors that are going to reproduce earlier than expected which could help drive quicker recovery if we don't see another heat stress this summer," he said.

"This is a positive news story for a change for the Great Barrier Reef. We're seeing eggs and we hope those eggs will lead to somewhat of a successful spawning season this summer."

AIMS researchers will continue to monitor the reefs to assess if it will lead to a successful spawning season.

"What we really need to understand now is if these eggs that are produced will mature and lead to viable eggs that can form coral larvae," Dr Cantin said.

The mass coral spawning event on the Great Barrier Reef occurs between October and December.