Yasi the green sea turtle has made a long-awaited return to Fitzroy Island off Cairns, laying seven nests of eggs from which more than 700 baby turtles have hatched.

Cairns Turtle Rehabilitation Centre marine biologist Jen Moloney said Yasi was believed to be between 60 and 80 years old, and last came to nest on the island in 2011 just before Cyclone Yasi struck.

"She made nine nests that year, 2011, but all but two were destroyed," she said.

The turtle was christened for the cyclone that destroyed her eggs, and scientists at Fitzroy Island had been hoping she would return ever since.

"We'd been waiting for her a couple of seasons ago, and even last season thinking, oh maybe, maybe, but she never made an appearance," Ms Moloney said.

"We started worrying that something had happened to her, but then lo and behold, she just had a snooze year, decided to wait a little bit longer before she came back."

Yasi finally returned to the island late last year and dug seven nests in the same places she laid her eggs seven years ago.

"Right at the end of November was when she made her first appearance, and then it was every one to two weeks after that she was popping up and digging another nest," Ms Moloney said.

While the scientists were not allowed to assist the hatchlings to the water, they fenced off the nests to ensure people did not disturb Yasi or trample her eggs.

Yasi is believed to be between 60 and 80 years old. ( Supplied: Cairns Turtle Rehabilitation Centre )

Perfect conditions for hatchlings

More than 700 hatchlings have since emerged and made a dash for the Great Barrier Reef.

"Because it's been awhile since the last time she came, there were no predators, there were no birds, the goannas didn't even find the nest," Ms Moloney said.

"We were worried about that, but it was perfect, they just all hatched and made a beeline for the ocean.

"We had the tree frogs chirping in the background, we had fireflies dancing around us, some of the nights the sky was just amazing.

"It was just lit up with stars as far as you could see, and then to top it all off, just hatchlings racing down the beach around us. It was just amazing."

Ms Moloney said only one in 1,000 turtles reached the age of 30, when they started breeding, and Yasi herself had almost certainly been born on Fitzroy Island.

"She's got to be one of ours, because they always come back to the same area they hatched in to nest, so she's definitely hatched here on the island and it's her turn to come back and make the next generation," she said.

Yasi is the only turtle to nest on Fitzroy Island in recent years.

"There used to be a lot more back in the 1980s, so we have seen a decrease, but we are hoping now with a bit more stability that we are going to get a few more adults coming back, especially with her new ones," Ms Moloney said.