Windermere has arctic charr, brown trout, pike, perch, roach and eels. Salmon and sea trout pass through the lake to spawn in the tributaries. Smolts (young trout or salmon) migrate downstream through the lake in spring, on their way to the sea.
Traditional boats are still used to fish for charr, a local delicacy.
Alien species compete with native plants and fish for space, light and food and may alter the ecological balance of the lake.
Canadian pondweed was the first to have a major impact, dominating depths greater than one and a half metres. In the 1970s Nuttall's pondweed replaced it as the major threat. And now Australian swamp stonecrop, also known as New Zealand pigmyweed, is spreading.
On river banks Himalayan balsam is a particular problem.
Lake users must clean equipment and clothing after using any lake or river to prevent the spread of alien species to other waterways.
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After the glacial waters of the last Ice Age receded, the arctic charr became land-locked in Windermere. There are at least four distinct and separate populations, with spring and autumn spawning populations in the north and south of the lake. Autumn spawners lay their eggs in relatively shallow water, while spring spawners use much deeper water.
Related to salmon, charr taste like a delicate version of sea trout and are popular potted or in pies. They are still caught on the lake today, in season from July to October.
The most successful method of catching charr is bright metal spinners being trailed on long lines deep into the water. Charr fishermen row along the lake to keep the lures moving continually.
To see the unusual colouring of these fish for yourself - silver, olive green and even scarlet - visit the Lakes Aquarium (opens in new window).
Check out the Environment Agency's River Levels web page (opens in new window)
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