Balaenoptera physalus physalus
Balaenoptera physalus quoyi
Common name: fin whale
HABITAT AND GEOGRAPHICAL DISTRIBUTION
The fin whale, scientific name Balaenoptera physalus of the Balaenopteridae family, is a cetacean found in all temperate waters (be they seas or oceans) of the world with the exception of tropical and polar waters. They are pelagic species but are sometimes also found in shallow waters at 30 m depth, near the coast.
It has been pointed out that there are two subspecies of fin whale according to the geographical distribution: the Balaenoptera physalus physalus which is found in the northern hemisphere and the Balaenoptera physalus quoyi in the southern hemisphere which differ not only in different genetic characteristics, but also in size, slightly higher in the southern whale than in the northern one. In consideration of the fact that the seasons in the two hemispheres are reversed, the two subspecies practically never meet as the epochs of migration have shifted in time.
The fin whale is a large gray-brown cetacean with a white belly, very elegant and very elegant, even in its movements.
They are whales of considerable size that reach 23 m in length with an estimated weight of 70,000 kg (estimated because they have never been weighed) making it the largest cetacean in the world after the blue whale.
Surely the most unusual feature of the fin whale is the asymmetrical coloring of the lower jaw (photo below), which is white or creamy yellow on the right side while on the left side it is dark in color. This asymmetrical coloring extends up to the baleen and the tongue (it seems that this different coloring helps in the capture of prey as a result of particular hunting techniques).
They have a V-shaped head, flat at the top, which has a sort of crest that goes from the blowhole to the tip of the rostrum (upper jaw). They have a series of grooves (about 85) running from the throat to the navel that serve the fin whale to expand the throat to hold more food.
Each side of the upper jaw has 350-400 baleen (photo on the side) which are dark-colored horny laminae made of keratin that replace the teeth of which they are devoid. The function of the baleen is to hold the fish and eliminate the water. Each baleen is about 30 cm wide and 76 cm long.
They have a very curved dorsal fin, about 60 cm high and very caudally displaced; the pectoral fins are small and tapered and the caudal fin is robust with powerful muscles that allow it to sustain a speed of 37 km / h.
It can descend to a depth of 250 m and remain submerged for an average of 15 minutes although it has been observed that it can remain submerged for longer periods.
CHARACTER, BEHAVIOR AND SOCIAL LIFE
The fin whale is a cetacean that can be found alone or in small groups, up to 6-7 individuals, although very large groups have been observed during migrations (up to 300 individuals).
They are migratory animals that migrate north in early spring, going towards high latitudes while in autumn they tend to return to lower latitudes.
They are cetaceans that stand out in powerful leaps out of the water.
COMMUNICATION AND PERCEPTION
The fin whale produces a great variety of low and high frequency sounds that can be heard at a considerable distance, in this way it is thought that groups of fin whales, even distant from each other, always remain in contact.
The fin whale eats numerous types of planktonic animals including crustaceans, squid and small fish. Its main diet is based on krill, small marine crustaceans similar to shrimps (in the Mediterranean it is its only food), belonging to the order of the Euphausiacea.
They can consume up to 2 t of food per day and the technique is to open their mouth wide and put a large amount of water and fish into their throat (the throat increases in volume according to the amount of food, thanks to the grooves): the water is eliminated thanks to the baleen (their function is to hold the fish) while the fish is swallowed with the help of the tongue (video on the side).
REPRODUCTION AND GROWTH OF THE SMALL
Fin whale is thought to be a monogamous species as male and female always travel together.
Mating takes place in winter and gestation lasts about 12 months at the end of which only one baby is born, 6.5 m long and weighing about 18 kg. The puppies are weaned when they reach 6-7 months of age which corresponds to a length of around 11-12m.
Sexual maturity is thought to be reached by females between the ages of 3 and 12 while in males between the ages of 7-8.
The fin whale, thanks to its size, has no natural predators except the large orcheosqualids that can prey on the young. Only man is the great predator of this mammal and has heavily hunted it (and continues to hunt it) until it almost reduces it to extinction.
STATE OF THE POPULATION
Balaenoptera physalus is classified in the IUNC Red list (2009.1) among animals at very high risk of extinction in the wild, ENDANGERED (EN).
The IUNC has estimated that in the last three generations (78 years) the population has dropped by 70% due to heavy commercial hunting carried out mainly in the southern hemisphere. In practice, it was the second most hunted whale species, in the twentieth century, after the blue whale. In the past, this whale has enjoyed some protection due to its speed and the fact that it lives in the open sea. Today, unfortunately, these characteristics do not save it from modern hunting techniques and modern technologies.
The IWC (IWC International Whaling Commission) in 1985/1986 made a moratorium on commercial fin whaling by setting the catch limit to zero (except for subsistence aboriginal fishing off the coast of Australia). coasts of Greenland) but this moratorium has not been recognized by Japan, Iceland and Norway who continue hunting for commercial purposes.
Secondary causes of the death of the fin whale are: collisions with ships, especially in the Mediterranean; accidental catches with fishing nets; underwater noise pollution which is becoming a threat to the migration of these cetaceans, given their dependence on sound for navigation.
The fin whale is listed in Appendix I of CITES, the Convention on Trade in Endangered Species, which is not recognized by Iceland, Norway and Japan.
Fin whales are also listed on Appendix I and II of the Convention on Migratory Species (CMS).
As part of the agreement for the conservation of cetaceans in the Black Sea, the Mediterranean Sea and adjacent waters, the ACCOBAMS agreement (in force since January 2001) was signed for which fin whales, together with other cetaceans, are protected from deliberate killing, attempts are made to protect their habitats and improve their knowledge.
(1) Image not subject to copyright: courtesy photo NOAA (National Oceanic and Atmospheric Administration) USA