Dead and sick baby turtles are washing up on Capricorn Coast beaches in numbers never seen before by researchers, after swallowing plastic.

The Department of Environment (DES) said an "unusually large number" of weeks old flatback turtles have been found on the west coast of Keppel Bay.

Chief Scientific Officer Col Limpus said fragments of floating hard plastics and soft plastics had been found in the post-hatchling turtles.

"The concern is that several of these turtles that have washed in have actually been compromised because they have been swallowing plastic debris.

"These little turtles feed at the surface and feed on plankton and they don't discriminate between plankton and our floating rubbish."

International study underway

Dr Limpus said many of the turtles had been tagged as hatchlings before they left a nearby major flatback nesting area.

"The Peak Island nesting population has been declining for some years and we haven't been able to understand why, and this may in fact be giving us some clue as to what is happening," he said.

Marine Parks staff and volunteers had been recording, photographing and collecting the turtles.

"These little post hatchling flatbacks and those that are dead are being stored frozen so we can do detailed analysis," Dr Limpus said.

Those found alive are being rehabilitated and released.

"We had one little turtle that's 8 centimetres long and it [had consumed] a piece of plastic film, glad wrap type of film, that was 5cm by 2cm," he said.

"But after it had been able to pass that piece of plastic it perked up and we were able to release it."

DES said those who come across sick or dead turtles should contact the wildlife hotline on 1300 130 372.

"We have a collaborative study with researchers in England that are looking at plastic problems in the Mediterranean, Caribbean and here in Australia," he said.

"Unfortunately the public are not aware of the study and so quite often they are burying the hatchlings on the beach or putting them out to sea immediately."

Impact on future numbers

Dr Limpus said plastic problems had increased in recent decades and no "solid solutions" had been found.

"It wasn't an issue back 40 to 50 years ago when we were in our early years of research, now it's a major problem globally," he said.

"This won't impact the next breeding season, it will impact the season when they are due to come back as adults.

"We are talking a couple of decades … this is going to impact breeding numbers in the future."