Common Fin-back whale
The common Rorqual ( Balaenoptera physalus ) is one of the species of baleinoptères the best known ones. After the Blue whale, and with a length of approximately 25 meters, it is the second larger animal having ever existed on planet and noisiest of the marine mammals. One finds it in all the oceans, like at sea the Mediterranean (between Corsica and the Riviera), it saw strong a long time, probably a hundred years. The species, protected, is regarded as threatened by IUCN.
Description
Aspect
The adult size can reach 27 meters in the Antarctic and 24 meters in the Arctic.The quite visible dorsal fin is in the shape of sickle inclined with less than 40 degrees and posted on one the posterior third of the body; it measures 60 centimetres. The rorquals have 56 to 100 grooves of the throat with the navel. Their back is ducted to the caudal fin; their muzzle is narrow, in the shape of V, with only one median longitudinal peak in front of the vents.
Each side of the upper jaw door 300 to 400 Pennon S) and absorbs up to 70 cubic meters of water. It closes its jaws then and rejects water through the pennons. Each filtering little to bring nearly 10 kilograms food, and each common fin-back whale can absorb up to 1.800 kilograms per day and in Pacifique north.
Characteristics
The common fin-back whale can traverse a distance of 300 km per day, and on this occasion to support a speed of 37 km/h with points to 40 km/h. The rorquals probably live until more than 90 years.The fin-back whale expires by breath every 30 seconds at one minute, several times of continuation, with each increase on the surface. The remainder of the body remains often submerged. One measured descents with nearly 600 m over durations of more than 20 minutes.
Common rorquals were observed carrying out jumps out of water.
Chorologie
Ethology
See also: Song of the whales
The common rorquals are more gregarious than the others rorquals. They often live in troop from 6 to 10 individuals, but one could observe groups going to 100 individuals. The majority of the singing exercises are it in Frequency modulation between 16 and 40 Hertz. Each emission lasts approximately 1 to 2 seconds and the various combinations of sounds occur in an order modulated during 7 to 15 min. These songs are repeated over long periods. Vocalizations are emitted with a sound power being able to reach 184-186 Décibel S for 1 μPa of sound pressure to 1 meter. They can beings detected to several hundred kilometers of their source.
It is estimated that the increase in the sound noise in the ocean gene the reproduction of the common rorquals by preventing the males and the receptive females to communicate between them.
Distribution
Their population is currently estimated at 100.000 individuals. As much of others rorquals, the common fin-back whale meets in all the seas of the sphere, of the tropics to the Arctic circle. They are absent only in the polar zones and in the seas isolated like the Red Sea, the Persian Gulf, the part is the Mediterranean and the the Baltic. Their density is highest in moderate or cold water. The population in the Mediterranean is estimated between 3 000 and 7 400 animals. The common fin-back whale prefers deep water beyond the continental shelf.
Populations of North Atlantic
The common fin-back whale migrates towards the gulf of the St. Lawrence in March; in June, it abounds in water of Newfoundland where it is shown with approximately 45 kilometers with the broad one. The populations seem to decrease.
Populations of the Mediterranean
Several censuses, carried out according to a strict methodology at the beginning of the Years 1990, estimated the number of rorquals alive in the Western Mediterranean, with between 3 000 and 4 000 individuals. It is the most common whale in the Mediterranean. According to the monitorings made in Gibraltar, there are very few exchanges between the populations of the Atlantic and those of the Mediterranean.
Migration
The rorquals common migrate every year of their zone of food to the zone of setting-low in hotter water. However the total model of migration is not well included/understood. Some rorquals prefer not to migrate during the summer months and to continue to nourish itself in colder deep water.
Threats
See also: Hunting for the whale
Like all the other large whales, the common fin-back whale was abundantly driven out. Between 1935 with 1965 close to 30 000 rorquals common per annum were killed and practically null since except the catches known as scientific. The current population is estimated to be roughly 40 000 specimens in the northern hemisphere and from 15.000 to 20.000 in the southern hemisphere. The Organochlorinated heavy metals, and the red muds threaten them.
Systematic
Since 1986, one recognizes two pennies species of common fin-back whale, largest B. p. quoyi (Fischer 1829) life in southern water and the B. p. physalus (Linnaeus 1758) in the northern hemisphere. The two subspecies are different by their songs. The majority of the experts consider that there exists a third subspecies, still anonymous. However, one does not know when the family members diverged between them.
See too
Related articles
External references
Sources
External bonds
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