A few days ago, the first sightings of fin whales this year were reported on the Catalan coast.
The fin whale (Balaenoptera physalus, Linnaeus, 1758) is the second largest animal in the world, after the blue whale. It is the only species of baleen whale that commonly inhabits Mediterranean waters and can measure up to 25 metres in the Mediterranean, although the average adult length is 18-22.5 m, with a weight of 90 tonnes.

In the Mediterranean basin, we can find individuals from two distinct subpopulations, the Atlantic and the Mediterranean. The latter is a resident population that uses opportunistic movement strategies within the central and north-western Mediterranean Sea (Geijer et al. 2016). While individuals of the Atlantic subpopulation enter the Mediterranean Sea through the Strait of Gibraltar between November and April and leave towards the Atlantic between May and October (Gauffier et al., 2018).

The fin whale in our waters

Every year, the fin whale visits the waters of the Catalan-Balearic Sea, between the coast of Catalonia and the Balearic Islands, mainly from March to June, where it feeds and migrates to other feeding areas, and later in autumn when it is mainly observed with travelling behaviour. Fin whales in this area are observed both feeding and migrating to other feeding areas. Later in autumn, they can be observed again, although in this case, more occasionally using the area as a staging area.

Migration of the fin whale

The fin whale is a species with seasonal movements.

Historically, minke whales have been described as making latitudinal migrations between areas of high productivity at higher latitudes in summer, where they feed, and areas at lower latitudes in winter, where they breed (Kellogg 1929). But as knowledge about these species increases, exceptions or doubts appear as to whether this theory is too simple for some of them.

This is the case of the fin whale in the Mediterranean.

The meteorological conditions and temperate climate of the Mediterranean Sea may have provided fin whales in the Mediterranean with a longer feeding period than in other oceans (Notarbartolo-di-Sciara et al. 2003). In the Mediterranean basin, feeding areas for this species have been detected throughout the year. Thus, in summer the waters of the Ligurian Sea and Gulf of Lions become aggregation areas for fin whales where they feed mainly on small invertebrates (krill and copepods).

After the summer months, the number of fin whales in northern Mediterranean waters starts to decrease, and they disperse throughout the Mediterranean Sea (Notarbartolo-diSciara et al. 2003, Panigada et al. 2017) for feeding, breeding and calving. In the case of other whale species, this movement would be understood as a movement towards breeding areas, but specific breeding areas haven’t been found at this time. In addition, calves have been observed throughout the year, so it is thought that they may use the whole Mediterranean basin for breeding and calving (Notarbartolo-di-Sciara et al. 2003).

For the Atlantic population, it is unknown how far into the Mediterranean they go, with authors believing that Atlantic individuals after entering the Mediterranean are distributed in the western region as far as the Balearic basin, while others believe they may go as far as the northwestern basin (Giménez et al. 2013, 2014). They are known to feed in the Mediterranean and it is believed that part of this community could also breed in this sea (Castellote et al. 2012) as juveniles have been observed leaving the Mediterranean between May and July (Gauffier et al., 2018).

Although knowledge about this species has expanded in recent years, many questions remain, such as the use and distribution areas by each subpopulation, winter distribution, the extent of interactions between Mediterranean and Atlantic resident whales, the importance of the Mediterranean habitat for whales from the Atlantic, as well as the movements of fin whales in the Mediterranean (Notarbartolo et al., 2016).

Respectful whale watching

During the next few months, these animals will be present in Catalan waters where they will feed and continue their journey to other areas. It is important to remember that in the event of an encounter with any species of cetacean, no boat may approach closer than 60 metres from the animal or group of animals. If an approach is made to observe them, it should be made gently at an angle of 30º, never head-on, from behind or perpendicular to their trajectory and always without cutting off the animals’ path. During observation, a constant speed should be maintained, and the course should be parallel to the direction of the animals. If possible, it is recommended to turn off the boat engines to reduce the impact on the animal.

In the same way, a special permit is required to fly over the animals with a drone. Royal Decree 1727/2007 of 21 December 2007, which establishes measures for the protection of cetaceans, contains general rules of conduct during cetacean-watching activities.