THIS year has been the first when the stocking of diploid trout – fish farm brown trout capable of spawning – was banned on rivers and streams in England and Wales.

This was done in an effort to prevent the further dilution of the genes of natural trout and therefore strengthen the stock.

From the start of this century, evidence had been mounting that angling clubs had been wasting money on restocking each year and data was compiled from extensive fishing rights of the Manchester Anglers (MA) on the upper reaches of the River Ribble that confirmed the evidence.

The MA had been stocking about 800 to 1,000 brown trout each season and anglers catch records showed that over 90per cent of catches were being returned.

These figures should have shown that the river would be full of trout but it wasn’t. This prompted a few questions.

Where were these fish going? Were they overwintering? Why was the river not teeming with trout ? What impact, if any, was the high stocking rate having on the wild fish population?

MA members were asked to record their season catches and in 2004 this showed that 403 brown trout had been caught and 90per cent returned.

In 2005, the restocking fish were fin clipped – adipose fin removed – and returns showed that 454 fish were caught and of these, 222 were fin clipped stocked trout.

In 2006 no stocking was carried out due to disease at the suppliers but 290 fish were caught with just three fish being fin clipped.

The season was hit by a drought and angling frequency was low. In 2007 the MA took the decision not to stock but catch returns recorded 350 fish with just one fish fin clipped.

Since 2007, catches have returned to the numbers achieved when restocking was carried out and now anglers are reporting catching plenty of small trout in the 7.5 to 20cm (3 to 8 inch) range and some adults up to 1,360g to 1,800g (3 to 4 lbs). These fish are now successfully spawning judging from the range of fish sizes.

Other Ribble angling clubs are now following suit after reviewing the evidence obtained from the MA’s experience of ceasing stocking. The Settle Anglers ceased stocking following a decision at their in 2012.

River stocking with sterile triploid trout is still permitted but the fish tend to be more expensive due to the process involved with sterilisation and are believed to have a tendency to move about excessively from their point of introduction. On the plus side they fight well and grow quickly.