As part of a scheme to monitor the distribution of otters throughout the UK, four Welsh otter survey have been carried out covering the years 1977-78, 1984-85, 1991 and 2002 (funded by the Nature Conservation Council, The Vincent Wildlife Trust - 1984-5 & 1991 - and the Environment Agency respectively). This database is currently only made up of the 1991 and 2002 surveys. Sites were selected by accessibility and likelihood of finding signs of otter activity - typically road bridges and the confluences of watercourses. The number of sites visited per hydrometric region varied. No attempt was made to randomise the sampling effort, but there was some site variability due different issues when the surveys were undertaken - 1008 sites have been consistently monitored over the four surveys. The number of spraints was recorded. Mink were recorded in this survey.
There are also Otter Survey databases for Scotland, England and Northern Ireland following the same protocol at differing resolutions.
