Otters were once hunted for their fur and were thought of as a pest, competing with fishermen for fish. In spite of these pressures, otters were widespread throughout Britain and the population remained steady until the 1950s when it declined rapidly. Otter-hunting was banned in England and Wales in 1979 and in Scotland in 1982. They are now rare or absent from lowland areas of England such as the midlands and the south.
The main reasons for the dramatic reduction in the number of otters has been disturbance and pollution. Since the 1950s riverside habitats have been drastically changed by farming and building techniques in addition to clearing for drainage. In other words, riverbanks have become far too tidy for the secretive otter. Watersports have also added to the disturbance of waterways.
Pollution of freshwater habitats has probably had the greatest impact on otters. The use of pesticides was greatly increased during the 1950s, particularly aldrin and dieldrin. These were washed off the land into rivers etc. and contaminated fish with tiny amounts of poison. Even though the fish may not be affected, the poison gradually accumalates in an otter eating a lot of fish, resulting in its death. Though most of these pesticides have been restricted since 1962, but residues still remain in the environment today. New chemical threats come from the build-up of substances like polybrominated dipehnyl ethers (PBDEs), which were commonly used as flame retardants in a wide range of household items including furnishings. PBDEs don't break down in the environment easily and have been shown to reduce fertility in humans. Though production of PBDEs is now controlled, they have been found at increased levels in a range of marine mammals.
In 2011 it was declared that the otter was again present in all of England's counties - a massive success as they had become very rare indeed. This success is due to better pollution control in our waterways and increased protection for this beautiful animal.
However, otters still face many threats to their survival, including chemical pollution (see above) roads, disturbance to their habitat and the fact that eels (one of their main foods) have declined by around 90%.