A rescue operation has cleared thousands of fish and a small colony of birds from the main reservoir at the Corus Rail site in Workington.
The reservoir, the size of a football field, had been a wildlife sanctuary in the middle of heavy industry for generations, but is redundant after steel rolling operations ceased five months ago.
The fish, mainly perch and roach, were removed by an Environment Agency team working under the supervision of River Derwent fisheries officer Denis McCartan and taken in tanks of oxygenated water for release at Mirehouse Pond, the Haig Anglers fishing water in Whitehaven.
The birds, including Muscovy ducks, a goose and a pair of peacocks, were captured by RSPB volunteers on the same day and taken to the wildlife sanctuary which is part of Silloth Holiday Centre.
They were transported in a cage which was built by Corus engineers and has now been given to the Knoxwood Wildlife Rescue centre at Aikton, near Wigton.
Other birds which made the reservoir home, including mallard and swans, have now relocated themselves naturally, though not without a hiccup.
A pair of swans landed on the reservoir shortly after it had been emptied and went into the mud rather than into the water.
Both were rescued uninjured, given a thorough cleaning and then released.
Estimates of the number of fish removed vary between 600 and 2,000. All were in superb condition and are thought to have been inadvertently pumped in to the reservoir as tiny fry from the River Derwent.
There were no signs of the carp introduced to the reservoir as algae eaters more than 30 years ago.
Mr McCartan said: “This was certainly a very different kind of operation from our normal work.
“The team tried at first to catch the fish by wading into the reservoir and catching them with seine nets but there was so much hidden debris on the floor of the reservoir that we had to abandon that idea and pump out the water.
“As the fish pooled we caught them in hand nets. We were happy to donate the fish for coarse angling to Haig Anglers because they have a well-run facility and they do a lot of good work in encouraging youngsters to fish.â€
