Fish stocks in the Huddersfield river were hit two years ago following a pollution incident, which damaged fish populations.
To help with the recovery of the river fisheries officers will be stocking it with grayling at several locations from below Marsden down to Milnsbridge.
Peter Mischenko, fisheries technical officer at the Environment Agency, said: “Grayling are an important species in a watercourse. They require water with a high oxygen content, and so their presence is usually a sign of good water quality.
“Anglers have come from as far afield as Holland to fish for them in the River Colne. This stocking should help to boost numbers in the river as part of an exercise that was started the year after the pollution incident.”
The young grayling are nearly five months old and have been bred and grown at the Environment Agency's fish farm at Calverton in Nottinghamshire.
The eggs come from adults caught from West Yorkshire’s River Calder back in March 2012, and the young fish, known as fry, have been grown in a specially designed system that ensures they can thrive in the River Colne.
The fry will continue to grow in the river and some of them will begin to spawn in the spring of 2014. It is hoped that by stocking these young fish over the next few years, the population of grayling in the river will return to healthy numbers.
