The DAERA Northern Ireland National Imposex Survey is a tri-annual (once every three years) assessment of the bio-effect of Tri-Butyl-Tin (TBT) on the dog whelk Nucella lapillus. Data is collected for the purposes of reporting to the EU Water Framework Directive (WFD), the EU Marine Strategy Framework Directive (MSFD), the Clean Safe Seas Evidence Group (CSSEG), and the OSPAR Commission.
