Expertise from across the Tasman is being used to try and find out why rainbow trout in some parts of the Snowy, such as the Eucumbene and Thredbo Rivers, appear to be declining, while brown trout numbers are holding.

A similar problem is being experienced at New Zealand's Lake Taupo, which has prompted NSW Fisheries to tap into the research conducted at that lake.

Researcher Dr Michel Dedual is being brought to the Snowy by NSW Fisheries.

The department is working in conjunction with the Monaro Acclimatisation Society which has for many years been involved with the trout in the high country.

Tackle shops and other industries associated with the trout such as hatcheries are also involved.

Acclimatisation Society President Steve Samuels says by involving someone like Dr Dedual, it's hoped that there'll be some solid research and not just anecdotes.

"Basically we want to know why in anglers catch numbers have dropped off.

"We're not prepared to say that there is a problem at this stage, but if we don't conduct some science and some research into it, we'll never know."