Oslo  - The illegal release of fish in a Norwegian lake has caused a Nepalese graduate student a severe headache and angered biologists, reports said Thursday.

Bishnu Regmi, who is studying insects in waters with and without predator fish for a doctoral dissertation, has to his dismay discovered that perch have been released illegally into the Myravann lake.

"This is really bad. I only get a study grant for three years," Regmi told the Bergens Tidende newspaper, saying that his 18 months of work may have been in vain.

"At worst, I will have to start with a different subject," he added.

Bergen University in western Norway has used the Myravann lake for various studies over the past 30 years.

The discovery of perch was unwelcome news, since there previously were only pike and eels among the fish species in the lake.

The perch were likely released some two, three years ago, according to biology professor Petter Larsson who said researchers have suspected the presence of perch due to an increase in plankton in the lake waters.

The special conditions in the Myravann lake have been used in numerous doctoral studies and other research papers.

Larsson said researchers feared an increase in algae blooming in the lake, adding that the release of the fish was "an ecological crime of the worst kind," the report said.

Local authorities said they were to investigate the matter and could possibly consider using poison to kill the unwanted fish species. (dpa)