Abstract
Harbour porpoises in the Iberian Peninsula form a genetically distinct, small (around 2900 animals) and isolated population. Their main prey are commercially important fish, hence overlap between porpoise occurrence and fishing activity is almost inevitable. We compile information on bycatch mortality, mainly collected over the last 15 years, based on on-board and land-based monitoring of fishing activity, analysis of cause of death and mortality rate based on strandings, and interview surveys with fishers. All these sources provide data of questionable reliability, for example due to low and incomplete coverage of fleets by on-board observers (indeed, essentially an absence of such data for the north coast of Spain (ICES area 8e). Nevertheless, all available estimates appear to suggest that the number of porpoises killed annually is likely to be unsustainably high. Despite some apparent incompatibility between abundance data, estimated bycatch mortality rates and genetic data, we suggest that both new mitigation action to reduce bycatch and improved monitoring are needed to secure the future of this population.