Under-threat fish which can be traced back to the Ice Age are to be airlifted to a new Lake District home.
The vendace fish are to be airlifted to cleaner waters
An RAF helicopter will be used to transport around 200 vendace from Derwentwater to nearby Sprinkling Tarn in the Borrowdale Valley, on Thursday.
The move was prompted by fears that poor water quality and pollution could wipe them out.
Vendace are small, white fish which live in cold water and are found in only two locations in the UK.
During the rescue mission, they will be caught in nets and placed in oxygenated tanks for the seven mile journey.
Large canvas bags, normally used to airlift rocks and materials for high Lake District footpath repairs, will be used to carry the tanks.
Environment Agency fisheries technical team leader Keith Kendall said: "Derwentwater has a population of around 15,000 vendace and will not miss the 200 we are hoping to move.
"We looked at three tarns, but went for Sprinkling because not only is it one of the closest to Derwentwater, but has the best environmental conditions for vendace."