Species: Balaenoptera physalus (Linnaeus 1758)
The fin whale is the largest cetacean in the Mediterranean Sea and the second largest animal on the planet after the blue whale (Balaenoptera musculus).
It is a Mysticete or a baleen whale, that is a cetacean with baleen, a filter-feeding structure that replaces the teeth and that allows the animals to feed on the small organisms of plankton, the krill. Fin whales’ body is slender and hydrodynamic, the length can reach up to 20 meters for a weight up to 70 tons; females are slightly larger than males.
Breathing at the surface, the animal emits long vertical blows sometimes up to 7 meters high; like for all the Mysticeti, the blowhole of the fin whale is provided of two orifices. The colouration is grey slate on the back and white on the belly. There is an asymmetry in the pigmentation of the head: the right mandibular region is white, while that of the left is dark. The fin whales carry out long apneas variable from 5 to 15 minutes and, before diving, whales arch their back high out of the water, but rarely raise their flukes out of the water.
The species is distributed throughout all temperate, pelagic waters, although it is sometimes observed at shallower depths. It feeds on both planktonic crustaceans and small fish.
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There is no population estimate for the Mediterranean Sea. Based on surveys conducted in the western Mediterranean, where most fine whales are concentrated, it seems realistic to assume that there are no more than 5000 individuals in the entire basin.
The most important threats are man-made: ship-strikes and bycatch in fishing gear. Other factors of disturbance are represented by whale-watching activities and noise pollution.
Fin whales in Ischia
The presence of the fin whale in the waters of Ischia is not constant. In the period 1997-2000, the fin whale was the most frequently sighted species in the study area, with a total of 66 sightings in three years. The animals were concentrated in the most coastal part of the Cuma Canyon system, north of the island, where they were observed feeding
Most of the time spent on the surface by fin whales was at sunset, which is probably associated with the vertical nyctemerial migrations of preyed Euphasiacea; on these occasions, whales were seen to emerge, with the mouth open, with vertical lunges. The analysis of faecal material has revealed the presence of crustacean exoskeletons belonging to the Euphasiacean Meganictyphanes norvegica, a key species in the pelagic trophic web, and the main food for the fin whales in the Mediterranean Sea. M. norvegica plays an essential role in the feeding of other groups of cetaceans, such as odontocetes, as it is also food for squids and fishes which are preys of these marine mammals.
In subsequent years, 2001-2019, the fin whale occurrence in the study area has become rarer.
The recent distribution of the fin whales in the study area shows that the animals are sighted in both, pelagic and coastal waters.