Contemporary migration of fin whales through the Strait of Gibraltar

Abstract

Fin whales Balaenoptera physalus used to be abundant in the Strait of Gibraltar and nearby Atlantic areas until their rapid collapse due to intense whaling at the beginning of the 20 th century. Recent studies seem to indicate that some fin whales, believed to belong to the North East North Atlantic (NENA) stock, now use the area to travel between the Atlantic Ocean and the Mediterranean Sea. In this study, we analyzed 15 yr of direct observations combining vessel and land-based surveys with photo-identification to characterize the migration of fin whales through the Strait. These combined observations provide a temporal and spatial analysis of the whales' movement patterns and behavioral activity. Our main findings suggest a migration of a small community of fin whales through the Strait of Gibraltar, with remarkable seasonal directionality. All whales travelled towards the Atlantic Ocean between May and October, and 69% towards the Mediterranean Sea between November and April. Observations of young whales exiting the Mediterranean Sea mainly between May and July suggest that at least part of this community is likely to calve in the basin. Due to the special sensitivity of the species to ship strikes and underwater noise, and the intense maritime traffic in the Strait of Gibraltar, we urge Spain and Morocco to cooperate through the International Maritime Organization (IMO) to ensure a safe crossing of these whales by the effective implementation and year-round extension of the existing recommendation of a seasonal vessel speed reduction to 13 knots.

Fin whale acoustic presence and song characteristics in seas to the southwest of Portugal

“…II (Methods) were produced between September 2007 and April 2008, which matches the period of highest fin whale vocal activity described in the literature for the Northern Hemisphere (Watkins et al, 1987;Watkins et al, 2000;Stafford et al, 2007). It also matches the peak for the southwest Mediterranean Sea and Strait of Gibraltar, as described by Castellote et al (2012), and the peak presence in the Strait of Gibraltar as described by Gauffier et al (2018). Between May and August 2008, there were no days with high quality bouts, and automatic detections were reduced considerably.…”

“…They also observed 69% of the sighted fin whales moving from the NENA toward the Mediterranean Sea between November and April. Considering the directional movements found in Gauffier et al (2018) and the seasonal presence of the acoustic characteristics found in this study, the results suggest that fin whales from the NENA may travel more frequently between the NENA and the Mediterranean Sea than Mediterranean fin whales may swim to the NENA. From the 37 bouts that were manually analyzed in this study, only four showed acoustic characteristics associated with Mediterranean fin whales.…”

“…Cluster 1 was recorded during several months of the study-between September and December 2007and between February and April 2008. Gauffier et al (2018 performed an extensive study of the movements of fin whales between the Mediterranean Sea and NENA combining data from direct observations, vessel-, and land-based surveys with photo-identification over a period of 15 years.…”

“…However, scientists have debated whether Mediterranean fin whales are currently moving into the NENA or not (Castellote et al, 2012;Gim enez et al, 2013;Castellote et al, 2014). Mediterranean fin whales have been assumed to be resident (Notarbartolo di Sciara et al, 2003), but the evidence showing that some individuals from the Mediterranean Sea travel toward the NENA is growing (Geijer et al, 2016;Gauffier et al, 2018). However, the frequency and the range of these excursions to the NENA are not clear (Notarbartolo di Sciara et al, 2003).…”

Crossing the Pillars of Hercules: Understanding transoceanic migrations of seabirds throughout their breeding range

“…The Strait of Gibraltar (SoG hereafter; 36.14°N, 5.35°W; Figure 2) is the narrow and shallow oceanographic connection between the Mediterranean Sea and the Atlantic Ocean. It represents a migration bottleneck for most migratory land birds moving between the European and African continents (Miller, Onrubia, Mart, & Kaltenecker, 2016), but also for those diverse marine species moving between the Mediterranean and Atlantic water masses (Abascal, Medina, Serna, Godoy, & Aranda, 2016;Gauffier et al, 2018;Mateos-Rodríguez & Bruderer, 2012). From last century, many migratory studies used SoG as observatory point for studying spring and autumn passages of diverse marine species because individuals concentrate in a relatively small area for short periods of time, making them visible and countable on board, using radars or even using telescopes from the coast (Garcia, 1971;Hashmi & Fliege, 1994;Silvani, Gazo, & Aguilar, 1999;Stephanis et al, 2008).…”