Fin whale (Balaenoptera physalus) population identity in the western Mediterranean Sea

Abstract

Archival bottom‐mounted audio recorders were deployed in nine different areas of the western Mediterranean Sea, Strait of Gibraltar, and adjacent North Atlantic waters during 2006–2009 to study fin whale (Balaenoptera physalus) seasonal presence and population structure. Analysis of 29,822 recording hours revealed typical long, patterned sequences of 20 Hz notes (here called “song”), back‐beats, 135–140 Hz notes, and downsweeps. Acoustic parameters (internote interval, note duration, frequency range, center and peak frequencies) were statistically compared among songs and song notes recorded in all areas. Fin whale singers producing songs attributable to the northeastern North Atlantic subpopulation were detected crossing the Strait of Gibraltar and wintering in the southwestern Mediterranean Sea (Alboran basin), while songs attributed to the Mediterranean were detected in the northwest Mediterranean basin. These results suggest that the northeastern North Atlantic fin whale distribution extends into the southwest Mediterranean basin, and spatial and temporal overlap may exist between this subpopulation and the Mediterranean subpopulation. This new interpretation of the fin whale population structure in the western Mediterranean Sea has important ecological and conservation implications. The conventionally accepted distribution ranges of northeastern North Atlantic and Mediterranean fin whale subpopulations should be reconsidered in light of the results from this study.

Potential feeding habitat of fin whales in the western Mediterranean Sea: an environmental niche model

“…6), which were both classified by Notarbartolo di Sciara et al (2003) as regions of intermediate importance. The Alboran Sea was recently suggested to be a wintering ground for the north-east North Atlantic population (Castellote et al 2012a). This is consistent with the observation of fin whales migrating through the Strait of Gibraltar towards the Mediterranean Sea in November/December and back from May to July (Gauffier et al 2009(Gauffier et al , 2011.…”

“…Similarly, particular observation effort should focus on the Strait of Gibraltar area to further characterize this observed cross-basin route (Gauffier et al 2009(Gauffier et al , 2011 and to evaluate the mixing of populations. If the seasonal migration of Atlantic fin whales through the Strait of Gibraltar is established, it could be assumed that at least 2 subpopulations of fin whales may co-exist in the southern Mediterranean Sea from December to April/May (Castellote et al 2012a), presumably in relation with breeding (Notarbartolo di Sciara et al 2003). …”

Ocean ambient sound south of Bermuda and Panama Canal traffic

“…At the same time, our timing is consistent with the recordings from the Gulf of Maine where songs with 15 s IPI were also recorded during the winter and early fall of 2006 (Delarue et al, 2009). Higher frequency components in North Atlantic fin whale calls have been reported previously in the Mediterranean and northeastern Atlantic, but also to the north of the Greater Antilles (Folkow and Blix, 1991;Castellote et al, 2012). Further investigation of these patterns may provide insights into the regional fin whale population structure.…”

Isotopic niches of fin whales from the Mediterranean Sea and the Celtic Sea (North Atlantic)

“…(Bentaleb et al, 2011) and from individuals caught off north-western Spain (Gim enez et al, 2013) suggest that, while the two subpopulations generally forage in well-differentiated areas, some individuals with characteristic North Atlantic values do penetrate into the Mediterranean Sea (Gim enez et al, 2013). Spatial and temporal overlap may exist between this subpopulation and the Mediterranean subpopulation (Castellote et al, 2012). However, connectivity between subpopulations or management units of whales inhabiting the eastern North Atlantic and the Mediterranean Sea is the subject of ongoing debate (Gimenez et al, 2014).…”

“…Genetic analyses based on both mitochondrial and nuclear DNA indicated differences between fin whales in the Mediterranean Sea, largely resident in the basin, and fin whales sampled in the Atlantic (B erub e et al, 1998;Palsbøll et al, 2004). However, acoustic analyses have demonstrated some interpopulation movements, prompting debate on the extent to which the two putative populations are geographically isolated (Castellote et al, 2014(Castellote et al, , 2012Gimenez et al, 2014). Stable isotope analyses of baleen plates from stranded whales suggest that whales from the Mediterranean and North Atlantic are largely discrete but with occasional exchange (Bentaleb et al, 2011;Gim enez et al, 2013;Ryan et al, 2013).…”