Non Native Species

Signal Crayfish are a North American species non-native to the Tweed but in recent years they have been found in several locations throughout the Tweed catchment.

The Bullhead is a species native to the South of England but not to the Tweed.  It has recently been found in a tributary to the Tweed.

Pink Salmon (native to the Pacific Ocean) were introduced to the Atlantic Ocean and are now occasionally found in rivers across Scotland, including the Tweed.

Giant Hogweed, native to the Caucasus Mountains and Central Asia, is an invasive species of plant found on the banks of the River Tweed.

Japanese Knotweed, native to East Asia, is one of the more common invasive non-native species throughout Europe and North America.

Himalayan Balsam is native to the Himalayas but has successfully spread throughout much of the Northern Hemisphere.

Gyrodactylus salaris is a freshwater external parasite of Salmon.  It is not yet found in the Tweed but if it does reach Scotland it could have a catastrophic impact on Salmon.

Killer Shrimp are a voracious predator and can do serious harm to freshwater ecosystems.  Killer Shrimp have not been found in the Tweed system but they have now been found in England.

The Chinese Mitten Crab reached Europe in the 20th Century and is now found in rivers throughout England, including the River Tyne.  This species poses a high risk if introduced to the Tweed.