River restocked after mystery pollution

Thousands of coarse fish were killed in the incident

A river in north Wales which was devastated by a major pollution incident last year has been restocked more than 50,000 fish.

The Environment Agency has announced it has added a further 1,800 mature coarse fish to the River Dee, which was hit by pollution last July.

More than 100,000 fish were killed, but the cause of the deaths remains a mystery.

The river had an excellent reputation for fishing

The river - a stretch of water which plays a number of important roles - is one of the most closely-regulated and controlled in Britain.

Not only is it regarded as one of the outstanding natural features of north Wales which provides excellent fishing, it is also a source of drinking water for almost three million people.

The restocking exercise, which began on Wednesday, is the second to take place since the disaster.

Pollution theories

Earlier this month, around 10,000 dace were put into the river to help replenish stocks, and this week 1,000 chub and 800 barbel were added.

The fish came from the Environment Agency's Calverton coarse fishery near Nottingham.

Experts say they stand a good chance of survival and reproduction due to their maturity, the good river conditions, and the fact that it is currently the closed season for coarse fishing.

Theories for last year's incident included industrial pollution or even deliberate poisoning - but investigators failed to find evidence of either.

Scientists are still not sure what was responsible although it was thought possible that the fish died from lack oxygen when a plug of deoxygenated mud was stirred up by heavy rain.