More than 7,000 young salmon are being released into ponds near the River Axe in east Devon on Thursday.
The young salmon will be released into Devon rivers in the spring
It is the latest move by the Environment Agency to help boost stocks in river in the region.
The young salmon, which are only a few inches long, are being brought down from Wales where they have been reared at the agency's hatchery.
Known as fingerlings, the fish were born from adult salmon which were trapped last autumn.
The salmon will be kept in the fish-rearing ponds where they will continue to grow and develop throughout the winter.
The Environment Agency says the measure will increase the salmons' chances of survival when they are released into the river next spring.
The River Otter and the River Culm, also in east Devon, will receive any surplus young salmon.
Andrew Locke, of the Environment Agency, is confident the attempt will work.
He said: "The survival rate of young fish reared at the hatchery in Wales has been very good this year."