More mutant fish have been found at a Noosa fish hatchery, including mullet embryos with two and three heads.

The discoveries come after seven mullet - four females and three males taken from the Noosa River, were given to the Sunland Freshwater Fish Hatchery at Boreen Point for breeding this month.

Two-headed fish eggs.

Fifty per cent of embryos found during two separate spawning events on July 5 and 6 had some form of cell abnormality, including some with two heads. A single mullet fry was found with three heads.

Some of the mutant eggs and embryos have been preserved for scientific testing, while authorities will attempt to retrieve seven mullet and other abnormal material after Sunland staff disposed of them.