Extinction fears as salmon disappear
By Western Daily Press | Friday, December 30, 2011, 09:00
Atlantic salmon that travel thousands of miles to swim up a West river could become extinct there within three years, environmentalists have warned.
The Wiltshire Avon, which drains most of south Wiltshire through Salisbury and on through Dorset, is one of the most important rivers for salmon in England, but a combination of milder climate and a loss of suitable breeding grounds has badly affected the numbers.
The Wiltshire Wildlife Trust said the number swimming back up the Avon has halved in the past five years, and there could be no salmon left in the river within three years.
The trust is now embarking on a new survey to discover what the problem is, and what can be done to help the epic swimmers.
The salmon hatch from eggs in the upper reaches of the Avon, often as much as 40 miles from the sea, in shallow gravelly stretches of the river and its tributaries like the Nadder, Wylye, Bourne and Ebble, which all meet at Salisbury.
Once a year old, the salmon then swim out to sea and spend their lives thousands of miles away in the north Atlantic, off the coast of West Greenland. There they live for years, before returning for a final journey back across the Atlantic, up the English Channel and into the mouth of the Avon in Dorset. They then have to find the exact tributary where they were born to spawn.
But Wiltshire Wildlife Trust director Gary Mantle said that surveys of the numbers accessing the mouth of the Avon at Christchurch, near Bournemouth, show that numbers have halved in just five years. Tests on stretches of the Wylye tributary which the wildlife trust owns and manages have also shown that the temperature of the water and other habitat information has changed and appears to be badly affecting the Atlantic salmon.
Oxygen levels, and the pH level of the water has changed, and the river appears to be a less salmon-friendly environment.
The trust is actively restoring sections of the river to create more gravelly shallows that the salmon prefer.
"We want to get into the river and clean the gravel so we provide a much better spawning area for the fish," said Dr Mantle.
"It's a range of activities that we can do and we need to make sure we conserve the fish so that the few that remain are protected as well," he added.
"In the next three years, salmon could be extinct from the river," he warned.
Salmon numbers took a nose dive in recent decades as the river quality was damaged by pollution caused by agriculture. Dredging the river to aid flood defences also damaged habitats, and extraction by water companies created a less healthy environment.