Improvements in water quality and subsequent fish stocks, in combination with the ban on the use of certain persistent pesticides have meant that otters have now returned to the Trent system, having been absent as recently as the 1980s. A survey in 2003 showed a doubling in the number of sites where evidence, such as spraints and footprints of these elusive animals were found. They have also now been sighted at locations such as Wolseley, Willington, and Attenborough. Seals have been reported up to near the head of the tidal section at Newark.