Salmon make a fast return in restoration
AS promised, here’s another good news story from the natural world; a river restoration project at Haweswater in the Lakes, which was aimed at helping breeding salmon, has spawned success only a few months after it was finished.
During the summer a one-kilometre stretch of Swindale Beck, which had been artificially straightened around two centuries years ago, was filled in and replaced with a more natural curving course through a partnership project between the RSPB, the Environment Agency, United Utilities and Natural England. This slowed the flow of the river, creating habitat more suitable for spawning salmon and trout, and in December 16 salmon were spotted in the new stretch of river.
Eggs are laid by female fish in gravel depressions called ‘redds’. As the eggs are released by the female, they are immediately fertilised by an accompanying adult male, and often by mature juvenile males (often referred to as ‘precocious’ parr).
The fertilised eggs are then covered with gravel by the female. Spawning occurs between November-December but in some localities, particularly in larger rivers, this may extend from October to late February. After spawning has taken place about 90-95 per cent of all Atlantic salmon die. Some do, however, survive and some may spawn twice or more.
Generally speaking, eggs usually hatch during early spring. These young fish, which still have a yolk sac attached, are called ‘alevins’.
These fish remain in the redd for a few weeks and emerge from the gravel in April or May, when they have absorbed the yolk sac and are about three centimetres in length.
The fish establish territories and compete with each other to feed on a range of items within the stream.
As these ‘fry’ get larger, they develop prominent markings on their sides and are then known as ‘parr’. Depending on the water temperature and the availability of food, they will live in the river for two to three years. Once they reach a size of up to 12cm, the parr undergo a physiological transformation which allows them to survive in marine environments.
The young fish, now called ‘smolts’, change in physical appearance, becoming silver, and start to leave the rivers during the late spring. Most of these fish will be gone by June.
Atlantic salmon already spawn in other areas of Swindale Beck, migrating from the sea via the Solway Firth and the River Eden.
However, the old straightened part of the river was too fast flowing for salmon to spawn, so the project has created new habitat by putting the curves back in this stretch of Swindale Beck.
The salmon eggs will hatch in spring, eventually emerging from the gravel after another four to six weeks. They will remain in the river for the next two to four years before migrating to the sea in spring time.
In addition to creating improved wildlife habitat, the restoration of Swindale Beck will have many other benefits, including helping to improve water quality as well as contributing to reducing the risk of downstream flooding.
Lee Schofield, RSPB Site Manager at Haweswater, said: “Habitat restoration is often a slow process and we normally don’t see the benefits of our work for years and sometimes even decades.
“It’s really uplifting and inspiring to work on a project where we get the chance to experience success so soon after we’ve finished.”
Oliver Southgate, River Restoration Project Manager at the Environment Agency, said: “This project demonstrates the true essence of partnership working. Everyone contributed throughout the project to ensure we delivered the maximum of benefits. It really does show that nature will find a way if you allow it to.
“It’s a brilliant project and another one for the UK River prize-winning Cumbrian river restoration programme.”