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  • Writer's pictureTees Rivers Trust

Migratory Fish: From Source to Sea

Around the world, numerous fish species are known to undertake migrations. Some fish, like salmon, migrate across vast distances covering thousands of kilometers, whilst others, like smelt, move between different locations in a relatively small area. Migratory fish use our rivers as pathways to reach their different required habitats, in order to complete their lifecycles.



Atlantic salmon migrating up a river


Migratory fish are either classed as catadromous or anadromous. Catadromous species primarily live in freshwater, such as the European eel. They will swim downstream as adults to the sea. Once there, they will continue to migrate across the sea to their preferred breeding place to spawn. When they have spawned, they will swim all the way back, returning to live upstream in a river. Alternatively, migratory fish can be anadromous. These species live in the sea, such as sturgeon. When they are grown-up and mature, these fish will swim to the shore and begin to ascend our rivers to breed upstream, before swimming all the way back down to live in the sea.


Over the last 40 years, it is now recognised that global migratory fish populations have continued to decline by 40% (World Fish Migration Foundation). Main factors that are causing this loss of these species are pollution, poor water quality and man-made barriers in our rivers. It is vital we look after and improve the health of our rivers to ensure that migratory fish can complete their full lifecycle so populations can survive and thrive.


European eel upstream


The Tees is home to a variety of different migratory fish species, particularly Atlantic salmon, trout and the critically endangered European eel! We are working hard to continue to improve our Tees Rivers to ensure migratory fish populations flourish.


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