Risk factors for cetacean species in western Mediterranean Sea through fixed-line transects monitoring
Author(s)
Campana, Ilaria
Date Issued
June 15, 2017
Type
Doctoral Thesis
Abstract
The Mediterranean Sea represents a particularly sensitive ecosystem for the coexistence of biodiversity richness and high levels of anthropogenic pressure, that can affect marine species in several ways. Cetaceans are considered good indicators of the status of marine waters, therefore monitoring their populations, together with their interactions with anthropogenic factors, are key elements in a conservation perspective.
Continuous research effort is effective to investigate temporal changes in species distribution together with impact factors, in order to highlight potential risk situations at early stage. The Fixed Line Transect Mediterranean Monitoring Network conducts regular surveys across the Western Mediterranean basin, using ferries as platform of research; the shared methodology provides standardised information about cetacean presence and potential threats, even in remote offshore areas and all year round. My PhD project aimed to improve knowledge about cetacean seasonal patterns of distribution and movements within the Western Mediterranean basin, and to investigate their relationships with maritime traffic and marine litter, considered among the major threats for these species. Using data gathered from the FLT Network, it was possible to explore these topics at large spatio-temporal scales, addressing several conservation issues within the current legislative framework.
Seasonal movements across the Sardinian-Balearic Sea were detected for the most frequent cetacean species (i.e. fin whale, striped dolphin and sperm whale) and significant hot spots and sensitive areas were identified in this basin mainly in spring/summer, due to the combined effect of high species diversity, abundance, clustering and presence of juveniles. Maritime traffic in the Sardinian-Balearic Sea showed the lowest intensity with respect to the Ligurian and Tyrrhenian Sea, and its influence on cetacean sightings seemed to have a minor effect, following a general decreasing pattern from spring/summer to autumn/winter, due to the combination of different intensity and composition of maritime traffic. Conversely, the identification of accumulation areas of floating litter (i.e. plastic) in all seasons suggested the presence of high pollution loads, representing a more relevant risk for many cetaceans species living in these waters.
On the other hand, this study showed the constant risk conditions which cetaceans face in the Ligurian Sea, due to the high density of maritime traffic and plastic pollution. In fact, these highly productive waters, included in the marine protected area of Pelagos Sanctuary, attract all cetacean species, that are sharing at the same time their favourable habitat with a strong anthropogenic pressure.
These results underlined the importance of improving research all year round to complete information about habitat use and movements of cetacean species at large scale, together with the trends of major risk factors through the basin. This study showed the effects of human activities on cetacean species, influencing their distribution and, presumably, their behaviour. In particular, in areas where the combined effect of different risk factors can impair the regular presence of the species with probable consequences at population level, this information represents a support for the implementation of adaptative conservation measures, even in offshore regions.
Additional information
Dottorato di ricerca in Ecologia e gestione sostenibile delle risorse ambientali