Thousands of green sea turtle hatchlings swim to sea in conservation win

The project to move eggs from one island has allowed for more males to develop. (Supplied: Queensland Parks and Wildlife)

It's believed 82 per cent of the northern Great Barrier Reef green sea turtle eggs relocated between two islands have hatched.

The species has faced increasing threats nesting on Raine Island, its main rookery.

Researchers say future testing will be needed to determine if the successful hatchlings are also the same fitness.

More than 9,100 northern Great Barrier Reef green sea turtle hatchlings have begun their journey to sea after a project relocating eggs between two islands achieved promising results.

It is the second time eggs have been moved from Raine Island to Sir Charles Hardy Island, about 600 kilometres north of Cairns in the north-east Coral Sea, in an attempt to boost hatchling numbers and produce more males.

Queensland Parks and Wildlife Service senior project officer Katherine Robertson said the latest results were encouraging.

"Of those eggs, 82 per cent of them hatched and the hatchlings made it to the water," she said.

Researchers collect eggs straight away as they are laid by female turtles. (Supplied: DETSI)

Raine Island, a tiny coral cay, is the world's largest nesting site for 90 per cent of the endangered species, and can attract up to 100,000 nesting females in a year.

However, rising sea levels, warming temperatures and climate change have created major threats at the rookery.

The turtle eggs are being destroyed by higher sea levels, and rising tides are creating steep slopes that hatchlings struggle to climb, which can cause them to flip and sometimes die.

Researchers collecting green sea turtle eggs on Raine Island. (Supplied: DETSI)

Sand temperature also affects the sex of the hatchlings, with warmer sand meaning fewer males.

"This population is almost entirely female," Ms Robertson said.

During the first relocation trial in 2024, teams moved 3,000 eggs from 38 nests, with 70 per cent of them successfully hatching.

This summer, researchers dramatically expanded the program, moving almost 9,000 eggs from more than 100 nests.

The eggs are placed in dug out nests under a shade on Sir Charles Hardy Island. (Supplied: Queensland Parks and Wildlife)

The eggs were carefully collected by researchers on Raine Island before being placed into oxygen-free vacuum-sealed bags, temporarily pausing their development.

Teams then took the eggs about 80 kilometres by boat to Sir Charles Hardy Island, where they were reburied beneath a custom shade structure.

It lowered sand temperatures by about 1.5 degrees