Activity
Otter Survey - Northern Ireland

Started 1977. Stratified non random sampling of all 10km squares in alternate 50km blocks in Northern Ireland. 1km squares selected and 600m transects walked along waterways. Detects changes in distribution between surveys but not trends in abundance. In the most recent surveys, 622 sites were covered in Northern Ireland. Survey power: National level surveys not originally designed to provide population trend information, but to provide presence/absence data and measure the rate of change in the distribution of the species over time. The report by Brewer et al. (2002) recommended a stratified sampling approach for the fourth survey of Scotland that would detect a 25% decline in otter distribution with 90% power.