Sharp decreases in survival probabilities in the long‑fnned pilot whales in Strait of Gibraltar

Pons, Miquel; De Stephanis, Renaud; Verborgh, Philippe; Genovart, Meritxell. Marine Biology 169 : 44 (2022)  DIGITAL CSIC  

The Strait of Gibraltar has some of the highest maritime activity in the world. Its populations of cetaceans are threatened by noise, chemical pollution, and collisions by the many boats crossing the strait. One of the greatest threats identifed in cetaceans in the Mediterranean are epizootics that severely afect the most sensitive vital rate in long-lived species: adult survival. By a multi-event analysis of a 16-year database of long-fnned pilot whale photo identifcation capture–recapture data, we analysed adult survival in the Strait of Gibraltar’s resident population and evaluated the possible efects of epizootics on this vital rate. We identifed the large efect of a morbillivirus epizootic that occurred in 2006–2007, but we also revealed a second collapse in survival in 2011, probably due to another morbillivirus epizootic. These episodes seem to afect sexes diferently, with females being less afected than males. Interestingly, the morbillivirus epizootic not only sharply decreased survival after the episode, but the efect extended over time, probably showing post-epizootic sequelae. These disease outbreaks have increased during the last decades worldwide and could be linked to anthropogenic threats such as organochlorine contamination. This may explain the high frequency of epizootics in the Gibraltar area. We warn about the conservation status of this long-fnned pilot whale population and recommend the application of measures to reduce contamination on this nutrient-rich area to improve conditions for many marine species inhabiting this area.