Trends in summer presence of fin whales in the Western Mediterranean Sea Region: new insights from a long-term monitoring program

Paola Tepsich; Ilaria Schettino; Fabrizio Atzori; Marta Azzolin; Ilaria Campana; Lara Carosso; Simone Cominelli; Roberto Crosti; Léa David; Nathalie Di-Méglio; Francesca Frau; Martina Gregorietti; Veronica Mazzucato; Clara Monaco; Aurelie Moulins; Miriam Paraboschi; Giuliana Pellegrino; Massimiliano Rosso; Marine Roul; Sébastien Saintignan; Antonella Arcangeli

doi:10.7717/peerj.10544

Trends in summer presence of fin whales in the Western Mediterranean Sea Region: new insights from a long-term monitoring program

PeerJ. 2020 Dec 14:8:e10544. doi: 10.7717/peerj.10544. eCollection 2020.

Authors

Paola Tepsich¹, Ilaria Schettino², Fabrizio Atzori³, Marta Azzolin^{4

5}, Ilaria Campana^{6

7}, Lara Carosso⁷, Simone Cominelli⁸, Roberto Crosti⁹, Léa David¹⁰, Nathalie Di-Méglio¹⁰, Francesca Frau³, Martina Gregorietti¹¹, Veronica Mazzucato⁷, Clara Monaco^{12

13}, Aurelie Moulins¹, Miriam Paraboschi⁷, Giuliana Pellegrino^{7

12}, Massimiliano Rosso¹, Marine Roul¹⁰, Sébastien Saintignan⁵, Antonella Arcangeli⁹

Affiliations

¹ CIMA Research Foundation, Savona, Italy.
² Department of Biology, University of Padua, Padova, Italy.
³ Capo Carbonara Marine Protected Area, Villasimius, Italy.
⁴ Life and System Biology Department, University of Turin, Torino, Italy.
⁵ Gaia Research Institute Onlus, Torino, Italy.
⁶ Department of Ecological and Biological Sciences, Ichthyogenic Experimental Marine Center (CISMAR), Tuscia University, Tarquinia, Italy.
⁷ Accademia del Leviatano, Maccarese, Italy.
⁸ NorthernEDGE Lab, Memorial University of Newfoundland, Newfoundland, Canada.
⁹ ISPRA, Rome, Italy.
¹⁰ EcoOcéan Institut, Montpellier, Francia.
¹¹ Department of Earth and Marine Science, University of Palermo, Palermo, Italy.
¹² Marecamp Association, Aci Castello, Italy.
¹³ Department of Agriculture, Food and Environment (Di3A), University of Catania, Catania, Italy.

Abstract

Background: The Mediterranean subpopulation of fin whale Balaenoptera physalus (Linnaeus, 1758) has recently been listed as Vulnerable by the IUCN Red List of threatened species. The species is also listed as species in need of strict protection under the Habitat Directive and is one of the indicators for the assessment of Good Environmental Status under the MSFD. Reference values on population abundance and trends are needed in order to set the threshold values and to assess the conservation status of the population.

Methods: Yearly summer monitoring using ferries as platform of opportunity was performed since 2008 within the framework of the FLT Med Network. Data were collected along several fixed transects crossing the Western Mediterranean basin and the Adriatic and Ionian region. Species presence, expressed by density recorded along the sampled transects, was inspected for assessing interannual variability together with group size. Generalized Additive Models were used to describe density trends over a 11 years' period (2008-2018). A spatial multi-scale approach was used to highlight intra-basin differences in species presence and distribution during the years.

Results: Summer presence of fin whales in the western Mediterranean area showed a strong interannual variability, characterized by the alternance of rich and poor years. Small and large groups of fin whales were sighted only during rich years, confirming the favorable feeding condition influencing species presence. Trends highlighted by the GAM can be summarized as positive from 2008 to 2013, and slightly negative from 2014 to 2018. The sub-areas analysis showed a similar pattern, but with a more stable trend during the second period in the Pelagos Sanctuary sub-area, and a negative one in the other two sub-areas. Our findings further confirm the need for an integrated approach foreseeing both, large scale surveys and yearly monitoring at different spatial scales to correct and interpret the basin wide abundance estimates, and to correlate spatial and temporal trends with the ecological and anthropogenic drivers.

Keywords: Assessment; Distribution; Fin whale; Mediterranean sea; Trends.

Grants and funding

The project was supported in 2011 by the French part of the Pelagos Sanctuary (Convention 11-011-83400), for the monitoring along routes in Pelagos. The project was supported in 2013 by ACCOBAMS, for the monitoring along routes between Italy and Tunisia. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.