Assessing sperm whale (Physeter macrocephalus) movements within the western Mediterranean Sea through photo‐identification

Abstract

ABSTRACT1. The Mediterranean sperm whale sub-population is considered 'Endangered' by both ACCOBAMS and the IUCN. Conservation policies require protected species populations to be monitored, but the distribution and movements of sperm whales across the Mediterranean Sea are still poorly understood.2. To provide insight into sperm whale movements, the photo-identification catalogue from the Strait of Gibraltar was compared with seven other collections: (a) the North Atlantic and Mediterranean Sperm Whale Catalogue (NAMSC), and with photo-identification catalogues from (b) the Alboran Sea, Spain, (c) the Balearic Islands, Spain, (d) the Corso-Provençal Basin, France, (e) the Western Ligurian Sea, Italy, (f) the Tyrrhenian Sea, Italy and (g) the Hellenic Trench, Greece.3. Of 47 sperm whales identified in the Strait of Gibraltar between 1999 and 2011 a total of 15 animals (32%) were photographically recaptured in other sectors of the western Mediterranean Sea in different years. None of the Strait of Gibraltar sperm whales were resighted in Atlantic waters or in the eastern Mediterranean basin.4. These results indicate long-range movements of the species throughout the whole western Mediterranean Sea, with a maximum straight-line distance of about 1600 km. The absence of any photographic recaptures between the Mediterranean Sea and the North Atlantic Ocean supports the genetic evidence of an isolated sub-population within the Mediterranean Sea.5. Long-term photo-identification efforts and data sharing between institutions should be further encouraged to provide basic information necessary for the implementation of effective sperm whale conservation measures in the whole basin.

An integrated approach for cetacean knowledge and conservation in the central Mediterranean Sea using research and social media data sources

“…Higher relative abundance was found at 800 m depth in the waters surrounding Ventotene island, between Ponza and Ventotene, and in a northern zone bordering the highly suitable area for fin whales. This seems consistent with previous studies reporting that sperm whales select for two main habitats: one where complex topographical features (escarpments, canyons, seamounts) characterize the sea floor and one where downwelling or upwelling water movements are associated with frontal zones in higher seas (Aïssi, Fiori, & Alessi, 2012;Arcangeli et al, 2017;Carpinelli et al, 2014;Fiori, Giancardo, Aïssi, Alessi, & Vassallo, 2014;Gannier & Praca, 2007;Mussi, Miragliuolo, Zucchini, & Pace, 2014;Pace, 2016;Pace et al, 2018). In this way, sperm whales would be able to capitalize on the food resources (cephalopods) available in both areas by shifting between different prey targets (Gannier et al, 2002).…”

Occurrence and spatio‐temporal distribution of sperm whale (Physeter macrocephalus) in the submarine canyon of Cuma (Tyrrhenian Sea, Italy)

“…In particular, three individuals (all immature males), showed transfers from north to south and vice versa, being recorded in both seas 1–2 months apart during a summer. This is analogous to other findings (Frantzis et al ., ; Carpinelli et al ., ), involving only males, thus suggesting that Mediterranean sperm whales behave in a similar way to those in other places, where males move between feeding and breeding grounds whereas females with their calves are more sedentary. Comparison between photo‐identification databases is still quite rare in the Mediterranean Sea, but the few recent attempts (Carpinelli et al ., ; Rendell et al ., ) have demonstrated that it could help to reveal new important information about sperm whale movements.…”

Abundance and movements of sperm whales in the western Mediterranean basin

“…The analysis of continuous movement showed diffusion rates (a quantification of the rate a population spreads spatially) dropping to zero over time scales >1 year (Figure (a)) and displacements stabilizing at 400–600 km over similar time‐scales (Figure (b)), indicating home range sizes in the order of 1000 km across, very similar to estimates derived for sperm whales in the Pacific. Noting that maximum straight‐line distance between any pair of identification locations reported here is 970 km, these results suggest that individuals use the entire western basin (see also Carpinelli et al ., ). The lagged identification rate analysis across areas supported this qualitative assessment in that there were non‐zero probabilities of re‐identification in different areas over time lags ranging up to >9 years (Figure ), but also indicated that the probability of an individual being re‐sighted in an area different from its first sighting was lower than the probability of being re‐sighted in the same area, suggesting some restriction of movement between the two areas.…”