Fin whale
Scientific Name: Balaenoptera physalus (Linnaeus, 1758).
Common Name: Fin whale.
Classification: Mysticeti (baleen whales), family Balaenopteridae.
Physical notes: Is the second longest animal on the planet, after the blue whale, can measure up to 27m and weight up to 120t, they have a long elongated body, a pointed head and a prominent, ‘swept-back’ dorsal fin. The upper body is dark grey, often with pale chevrons on the back and flank area behind the blowholes; the underside is white; the left lower jaw is dark and the right is white.
Distribution and habitat use: Cosmopolitan distribution, present in both Hemispheres from tropical waters to sub-polar waters, being absent in equator. In Portugal they occur mainly in waters from 200 to 3000m deep, outside the continental slope. In the north-east Atlantic seems to prefer waters between 16 and 19ºC with depths between 1000 and 3500m. Has complex migration patterns, with some individuals remaining at high latitudes during the winter and those that migrate south seemingly feeding along the way.
Group size: Mainly solitary animals, often in small groups of 2-7; loose aggregations of several dozen may occur in highly productive areas. Group composition tends to be dynamic.
Life span: 75 to 100 years (max 135).
Gestation period: 11-12 months. Calves are born with ca. 6m long and 3500kg. Females reach maturity at 6-10 years and males at 8-12 years. Mating occurs in October-December with calves being born the following winter in warmer waters. Juveniles are weaned after 6-7 months.
Diet and Feeding: Opportunistic, depending on locality, season and availability. In the North hemisphere feeds mainly on krill, copepods, schooling fish and small squid. Feeds intensely in summer, consumes much less in winter, by engulfing or lunge-feeding. They can dive up to approximately 500m and hold their breath up to 25 min.
Typical Behaviour: Fast swimmer, capable of up to 37km/h in short-bursts. Rarely breaches. Typically, neither avoids boats nor approaches them, but it can be quite approachable and is sometimes curious. They generally dive for 3-10 min, rarely showing the fluke. Very tall, columnar blow up to 10m high.
Population: Minimum c. 150 000 individuals worldwide. In Portugal, up to 50nm, the estimates of abundance at the end of the summer were 627 individuals between 2010 and 2015. Population trend is increasing.
Threats: Collisions with boats are one of the most reported threats; by-catch also occurs but is rare. Noise pollution has been identified as a potential threat, although its effect on populations is unknown. Increased marine traffic can alter the whale’s acoustic behaviour and reduce the distance at which vocalisations are detected, thus affecting reproductive success.
IUCN status: Vulnerable for overall species worldwide (2018), including Portugal (2023) and the Mediterranean sub-population (2021).
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