Fin Whale – Balaena physalus
Habitat: Deep waters (400 – 2000 m depth) off edge of continental shelves. Some localities in shallower waters. Appears to favour topographically diverse areas with underwater sills or ledges, upwellings, and frontal zones between mixed and stratified waters with high zooplankton concentrations.
Description: Large, slender whale. Head is v-shaped, slender, with prominent median ridge. Body is dark grey to brownish grey without mottling, white below, with white on surface of flukes, inner surface of flippers. Left side of head is dark, right side has white markings on lip and palate; most have pale grey chevron on each side behind head, may have dark stripe running up and back from eye, light stripe arching down to where flipper joins body. Throat has 56 – 100 grooves ending around the navel. Baleen plates relatively short (max 72 cm long x 30 cm wide), 260 – 480 on each side of upper jaw. Plates on right side usually yellowish-white for 75 – 100 cm from front end; remaining plates on right side, and all of left side, are slate grey with alternating longitudinal yellowish bands. Plates have brownish grey to greyish white fringes. Dorsal fin around 1/3 along back from tail. Flukes are broad, triangular, with slight median notch and slightly concave trailing edge.
Size: 18.5 – 20 m average; females larger, occasionally up to 24m.
Weight: 20,000 – 80,000 kg, larger in southern hemisphere.
Lifespan: 85 – 90 years.
Distribution: Worldwide, mainly in temperate and polar seas. Populations in polar seas may migrate south in winter; populations around British Isles appear present year-round. Most sightings in northern Great Britain occur June – August, sightings further south in September – February.
Diet & Feeding: Feeds mostly on euphausiids (krill) and copepods, but also takes cephalopods and fish such as herring, sandeels, mackerel. Engulfs prey from behind by distending throat grooves and taking large gulp of water. Coordinated swimming amongst several surface-feeding whales observed in south Mediterranean.
Breeding: Births occur mainly in autumn and winter. Gestation period 11 – 12 months. Lactation 6 – 7 months. Females reach sexual maturity at 6 – 10 years, males at 8 – 12 years; exploited populations seem to mature earlier. Calving interval around 3 years.
Conservation Status & Population: Listed by IUCN as endangered. Current North Atlantic population unknown, but possibly >46,000, including 17,000 for the British Isles-Spain-Portugal stock.
Historically heavily exploited. Currently accidentally caught in fishing gear only occasionally. Collapse of capelin stocks off Newfoundland in late 1970s thought to have reduced summering populations. Levels of contaminants such as PCBs and mercury are usually low compared to other marine mammals. Noise and disturbance from vessels and industrial activities may have negative impact in costal areas. Seismic sounds from oil and gas exploration along SE Atlantic shelf break may have negative imapct. Collisions between fin whales and vessels are known, including in British waters.
Second largest whale. Uniform slate grey colour (unlike mottled Blue Whale). Asymmetric white markings on right side of lip diagnostic. Blow is 4 – 6 m, cone shaped. Dives in long, highly arched (unlike Sei Whale), rolling motion, showing dorsal fin but generally not flukes.
Vocalisations: Mainly low-frequency pulses and moans, usually FM downsweeps but sometimes constant frequency, upsweeps, or wavers at around 4 to 17 Hz (can reach up to 125 Hz), lasting 0.5 – 1 s and often repeated in series with regular interpulse intervals of 5 – 45 s. Short sequences (2 – 30 repititions) are produced by both sexes and probably serve for communication over distances of 30 km or more. Long patterned sequences (up to 30 h, with 20 min rest periods) produced by adult males in October t0 April, probably reproductive song displays. Additional sounds include long rumbles (around 30 s) at 10 – 30 Hz with extensive frequency and amplitude moderation, and high frequency clicks (16 – 28 kHz, 8.8 s).