DNA samples have been taken from North East sea trout to try to follow its migration patterns and boost stocks.
The aim of the Living North Sea project is to discover why fish stocks are in decline.
Scientists from the Environment Agency are hoping to track individual stocks through their lifecycles.
Fish DNA has been collected for analysis from the rivers Coquet, Wear, Tyne and Tees.
The project involves 15 partners from seven countries including the Association of Rivers Trusts, the Norwegian Institute for Nature Research and the Dutch Angling Association.
Phil Rippon, project manager for the North East Living North Sea project, said: "Our work is part of a bigger genetics project which involves taking samples from sea trout stocks throughout the North Sea area, from countries such as Norway, Sweden, Denmark, and Scotland.
"It is believed sea trout stocks in different rivers are genetically different and it should be possible to track individual stocks throughout their lifecycles once a genetic fingerprint is established.
"The information will help us to identify where individual river stocks migrate to in the North Sea and whether they stray back to different rivers."
The DNA samples have been sent to Living North Sea partners in Denmark to be analysed.