Thousands of young salmon are to be released into the River Taff in an attempt to reinstate the fish back into the south Wales valleys.
The fish was virtually wiped out in the area
Salmon were almost wiped out in the area because of industrial pollution.
Heavy industry and mining in the area affected many of the rivers and by the early 1980s salmon were at very low numbers in the River Taff.
Around 5,000 young salmon will be put into the river which experts hope will swim as far north as Merthyr Tydfil.
Since the 1980s the rivers have been cleaned up and fish stocks introduced as well as fish passes built to encourage them upstream.
Although the affect of the Cardiff Bay barrage since its construction in the late 1990s is still being monitored, it is thought that as many as 300 salmon now enter the Taff every year.
Some are reaching as far as Merthyr Tydfil to spawn for the first time in 200 years.