Mink are not a native species. They were introduced to the UK where they were farmed for their pelts - skins, which were used to make fur coats. Something that would never happen today.  Unfortunately some of the mink escaped from farms, where they were kept in captivity, and can now be found on rivers and streams across the UK. They are a semi aquatic carnivorous mammal and are very damaging to British wildlife and can empty a river of fish in no time at all. To control their numbers mink traps are used and the standard tool is a Mink raft as shown here.