Estimating cetacean density and abundance in the Central and Western Mediterranean Sea through aerial surveys: Implications for management

Abstract

Systematic, effective monitoring of animal population parameters underpins successful conservation strategy and wildlife management, but it is often neglected in many regions, including much of the Mediterranean Sea. Nonetheless, a series of systematic multispecies aerial surveys was carried out in the seas around Italy to gather important baseline information on cetacean occurrence, distribution and abundance. The monitored areas included the Pelagos Sanctuary, the Tyrrhenian Sea, portions of the Seas of Corsica and Sardinia, the Ionian Seas as well as the Gulf of Taranto. Overall, approximately 48,000 km were flown in either spring, summer and winter between 2009-2014, covering an area of 444,621 km 2 . The most commonly observed species were the striped dolphin and the fin whale, with 975 and 83 recorded sightings, respectively. Other sighted cetacean species were the common bottlenose dolphin, the Risso's dolphin, the sperm whale, the pilot whale and the Cuvier's beaked whale. Uncorrected model-and design-based estimates of density and abundance for striped dolphins and fin whales were produced, resulting in a best estimate (model-based) of around 95,000 striped dolphins (CV=11.6%; 95% CI=92,900-120,300) occurring in the Pelagos Sanctuary, Central Tyrrhenian and Western Seas of Corsica and Sardinia combined area in summer 2010. Estimates were also obtained for each individual study region and year. An initial attempt to estimate perception bias for striped dolphins is also provided. The preferred summer 2010 uncorrected best estimate (designbased) for the same areas for fin whales was around 665 (CV=33.1%; 95% CI=350-1,260). Estimates are also provided for the individual study regions and years. The results represent baseline data to develop efficient, long-term, systematic monitoring programmes, essential to evaluate trends, as required by a number of national and international frameworks, and stress the need to ensure that surveys are undertaken regularly and at a sufficient spatial scale. The management implications of the results are discussed also in light of a possible decline of fin whales abundance over the period from the mid-1990s to the present. Further work to understand changes in distribution and to allow for improved spatial models is emphasized.

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

“…While the limited survey effort in some part of the basin, does not allow for an effective abundance estimation, our dataset is catching an intra-basin variability, which can result from a redistribution of the species. The differences about rich or poor years found by our study reflect the different results in abundance estimates for the Pelagos Sanctuary obtained by Panigada et al (2017) and Laran et al (2017). Indeed, for the second assessment, surveys were performed in a peaking year (2012), while the aerial surveys dataset from 2009 and 2010 were used by Panigada et al (2017).…”

Abundance, activity and critical habitat of the striped dolphinStenella coeruleoalbain the Gulf of Taranto (northern Ionian Sea, central Mediterranean Sea)

“…The ordinary Kriging maps predicted for each activity were transformed into binary maps using the corresponding cut-off values (Table 5). Therefore, the binary maps generated within each activity The overall density value estimated for S. coeruleoalba in the present study (0.97 specimens/km 2 ) is the highest among those reported for both the eastern (Bearzi, Bonizzoni, Agazzi, & Gonzalvo, 2011;Panigada et al, 2017;Santostasi, Bonizzoni, Bearzi, Lavinia, & Olivier, 2016) and western Mediterranean regions (Cotté et al, 2010;Forcada et al, 1994;Forcada & Hammond, 1998;Forcada, Notarbartolo di Sciara, & Fabbri, 1995;Gannier, 1998;Gómez de Segura, Crespo, Pedraza, Hammond, & Raga, 2006;Gómez de Segura, Hammond, Cañadas, & Raga, 2007;Lauriano, Panigada, Cannieri, Zeichen, & Notarbartolo di Sciara, 2010;Panigada et al, 2017;Panigada, Burt, Lauriano, Pierantonio, & Donovan, 2009;Panigada, Lauriano, Burt, Pierantonio, & Donovan, 2011). However, in these latter studies, much larger areas were considered and different observation platforms and estimation methods were used, thus caution is required in any further comparative considerations.…”

Looking beyond the horizon: An early warning system to keep marine mammal information relevant for conservation

“…The Pelagos Sanctuary for Mediterranean Marine Mammals, located in the north‐west Mediterranean, represents a landmark tripartite agreement between France, Italy, and Monaco approved in 1999 and signed by key parties (Notarbartolo di Sciara, Agardy, Hyrenbach, Scovazzi, & Van Klaveren, ). The agreement to protect territorial waters of each country and the high seas beyond was designed to conserve marine mammals of the north‐west Mediterranean's Ligurian Sea, including fin whales, sperm whales, Cuvier's beaked whales, short‐beaked common dolphins, bottlenose dolphins, long finned pilot whales, Risso's dolphins, and striped dolphins (Panigada et al, ). The existing boundaries of the Pelagos Sanctuary for Mediterranean Marine Mammals presently intersect the main feeding areas for fin whales (Notarbartolo di Sciara & Agardy, ), but secondary production (euphausiids) important for fin whale feeding also occurs outside the boundary, as demonstrated by Druon et al () in model‐based analyses.…”