Coastal seabirds and marine mammals are good indicators of the health of marine ecosystems and high mortality events of these species can signal changes in oceanic conditions, such as those caused by oil spills, fisheries, habitat loss, lack of food supply and extreme weather conditions possibly resulting from climatic changes. Surveys of beached birds and mammals are thus highly informative and provide a valuable tool to address the causes and rates of marine animal mortalities. Information collected from those surveys helps understanding local patterns in mortality, the time of the year when mortality is most severe, which species are most vulnerable, and allows quantifying the number of animals affected. When conducted routinely, beach surveys provide baseline information against which any exception al mortality event can be quantitatively assessed (e.g. due to oil spills or extreme weather conditions) and, for instance, to address whether human activities are hazardous for seabirds and marine mammals (e.g. oil spills and entanglement in fishing gear).
In early 2014 massive seabird mortality was reported along the coasts of southern England, SW France and northern Spain, where thousands of live and dead birds were found ashore by the end of February. This seabird wreck is amongst the worst ever recorded and was possibly caused by severe and continuing storms in the Atlantic Ocean . Unusually high numbers of dead seabirds were also reported in the Portuguese coast in late February (Van Nus & Moreira 2014a,b). Task-force work to rescue live birds and to record the magnitude of the event was promptly put in place in many European countries but, to our knowledge, Portuguese authorities and NGOs did not organize any surveying of its beaches. Upon knowing about the seabird wreck we decided to voluntarily survey beached seabirds near Aveiro so as to provide information for a stretch of the Portuguese coast . The beach extending from São Jacinto to Torreira (10 K m) located in NW Portugal suited our goal because it is not regularly cleaned and is partly closed off to the public. When receiving permission from the Reserva Natural das Dunas de São Jacinto to include the reserve’s beach in the study we conducted two surveys on March 14 and 27, 2014 (Van Nus & Moreira, 2014a,b). The reporting of our findings contributed to a better understanding of the geographical magnitude of the 2014 seabird wreck (http://www.oiledwildlife.eu/news/final-update-2014-european-seabird-wreck).
Following our surveys at the aftermath of the 2014 seabird wreck, we continued surveying the same beach transect on a regular basis, aiming to provide a year round picture of the mortality of marine birds and mammals. Here, we report the findings from twelve surveys conducted from March 14, 2014 to March 23, 2015.