The 25-mile long stretch of the Avon from Christchurch, Dorset, to Salisbury, Wiltshire, is now teeming with roach, to such an extent the project is being scaled back as there is now a sustainable population.
And the scheme has been hailed such a success by the Environment Agency and Natural England that is being rolled out to rivers in other parts of the country – the Kennet in Wiltshire, the River Severn and the Suffolk Stour.
Mr Harrop, from Ringwood, Hampshire, said: “We have put back thousands and thousands of young roach into the Avon. We think we have now tripped it back into a much more healthier state.
“You can now walk over bridges on the Avon at places like Ibsley and see huge shoals of fish in areas that were all but devoid of fish 10 years ago.
“People are catching roach up and down the river. One man caught 49 in one afternoon and that hasn’t been heard of in decades.
“We are going to do one last spawn collection and then let the project wind down over the next three to five years because the population will carry on recovering.