Razorbill Alca torda mortality in the Portuguese west coast

This study presents data on mortality events of the species Alca torda in the central region of Portugal and data was also used to improve reporting of species biometrics in wintering grounds. A total of 646 razorbills were collected between Aveiro and Praia de Santa Rita (central coast of Portugal) from January to April of 2012, 2013, 2014 and 2016. This species is listed as Near Threatened and population estimates are declining. The present study revealed an important bycatch-based mortality of razorbills in good body condition and evidence indicating entanglement in fishnets and drowning as the birds’ main cause of death. This study also revealed a significant increase over the years in wing length of sub-adults in their wintering range. Further long-term studies are necessary to verify the significance at population levels of the high bycatch mortality in this area (mainly due to IUU fisheries) and of the possible wing length increase of migratory razorbill sub-adults.