Biological recording underpins the conservation assessment of designated species: the recent case studies of the endangered white-clawed crayfish and near threatened otter

Biological recording underpins conservation of protected species, providing essential evidence for long-term trend assessment. Two recent studies demonstrate the value of combining field surveys with records held and curated by the Centre for Environmental Data and Recording (CEDaR) and the National Biodiversity Data Centre (NBDC).<br/><br/>The endangered white-clawed crayfish (Austropotamobius pallipes) and near threatened otter (Lutra lutra) were originally designated under the EU Habitats Directive, with UK reporting now under Habitats Regulations Reporting (HRR), requiring conservation status assessment every six years.<br/><br/>In 2024, crayfish were detected at 45% of 110 Northern Ireland sites using an environmental or eDNA survey. Integration with 1,336 CEDaR species records suggested its distribution was largely stable but strongly restricted by calcareous geology. Crayfish were more frequent at sites with recent records (suggesting vulnerability to local extirpation), rivers over lakes, and habitats with cobble or boulder substrates. They were vulnerable to agricultural pressures on water quality with occurrence significantly reduced by livestock access to watercourses, lowering detection probability by one-third. No crayfish plague was detected, but several designated sites showed evidence of population loss or decline, raising concerns for their long-term viability within Areas of Special Scientific Interest (ASSI) where crayfish are a designated feature.<br/><br/>In 2023-24, otter were detected at 65% of 919 sites in the Republic of Ireland and 66% of 144 sites in Northern Ireland using a tracks and signs survey. Analysis suggested a long-term decline of on average 24-27% since the 1980s, with losses of up to 40% in the Neagh-Bann River Basin District. Otters were associated with large, fast-flowing rivers with rocky substrates, riparian woodland, and unmaintained banks, and angling (salmonid prey availability) but negatively associated with peatlands. Combining survey results with species records held by CEDaR and the NBDC generated a database of 10,509 otter records with analysis suggesting a largely stable distribution over time despite apparent population decline.<br/><br/>Together, these studies highlight the indispensable role of long-term biological recording and curation by CEDaR in documenting species status, guiding survey design, validating eDNA detections, and contextualising results across space and time. With continuing pressures on water quality, robust networks linking citizen science, data repositories and professional surveys through research remain central to statutory biodiversity reporting and effective conservation.