OSPAR request on indicator assessment of coastal bottlenose dolphins

• Main Author: ICES
• Format: Report
• Language: unknown
• Published: ICES Advice: Special Requests 2022
• Subjects: Atlantic, Northeast ICES Ecoregion; FAO area 27; Fisheries and aquaculture; Oceanic Northeast Atlantic ICES Ecoregion; Northeast Atlantic
• Online Access: https://dx.doi.org/10.17895/ices.advice.18686933.v1; https://ices-library.figshare.com/articles/report/OSPAR_request_on_indicator_assessment_of_coastal_bottlenose_dolphins/18686933/1

ICES has collated all available relevant data on coastal bottlenose dolphins, Tursiops truncatus , in the OSPAR Regions II, III, and IV. Most data are from small-scale surveys at particular sites within the bottlenose dolphin assessment units (AUs). A large variation in the intensity and coverage of survey effort leads to strong spatial biases in data availability, making assessment at an AU scale challenging. Only five sites have sufficient data to allow assessment of trends in abundance. One of the sites withsufficient data showed a decline beyond the target threshold. Abundance estimates for bottlenose dolphins typically have wide confidence limits, and the power to detect even relatively strong trends may be limited. If the abundance of coastal bottlenose dolphins is to be used as an indicator, then either monitoring will need to increase to cover the entirety of each assessment unit at frequent intervals, or the relationship between the abundance of local groups and that of the assessment units would need to be determined. Both of these options would require the investment of further resources.