Reference points for assessing significant adverse impacts on deep sea vulnerable marine ecosystems

• SAI thresholds for 7 Vulnerable Marine Ecosystems are proposed. • Bottom trawling impact-risks are assessed for 7 Northwest Atlantic VMEs. • Large differences in VME sensitivity to bottom trawling activities are quantified. • Conservation targets to protect 60–70 % of deep-sea VME biomass are proposed. • Rapid loss in VME biomass is observed at a bottom trawling intensities of about 0.10 km·km −2 ·y -1 . Biodiversity loss due to human activities is a critical issue, particularly in the High Seas where bottom-contact fishing poses a significant threat to Vulnerable Marine Ecosystems (VMEs). Deep sea VMEs, tend to be composed of slow-growing, long-lived benthic organisms such as deep-sea corals and sponges. The United Nations Food and Agriculture Organization (FAO) has developed guidelines to protect these ecosystems from Significant Adverse Impacts (SAI) caused by bottom trawling activities. This study focuses on the Northwest Atlantic Fisheries Organization (NAFO) Regulatory Area, utilizing fishery-independent surveys and fishing Vessel Monitoring System (VMS) data to map fishing intensity and VME functional type biomass. Seven VME types have been assessed, e.g., large-sized sponges, sea pens, sea-squirts, bryozoans, black corals, large and small gorgonian corals, to determine the risk of impact. Results indicate that sponges, black corals, and large gorgonians are the most sensitive VME types to bottom trawling activities, with significant biomass loss occurring at very low fishing intensities. The study defines bottom trawling biomass impact thresholds for each VME type in the range of 0.12–9.43 km·km −2 ·yr −1 and 0.01–0.11 km·km −2 ·yr −1 for upper and lower impact thresholds, respectively. The study determines that rapid losses in VME biomass occurs at bottom trawling intensities of about 0.10 km·km −2 ·y -1 for fisheries operating in the NAFO Regulatory Area. The study concludes that modest reductions in fishing effort in sensitive areas could substantially mitigate SAI whilst having little or no impact on fishing opportunities. The findings also support the target of protecting at least 60 % to 70 % of VME biomass to likely ensure good seabed status; and the importance of implementing spatial fisheries management measures, such as defining a fishing footprint and establishing fishery closed areas, to protect VMEs.