Fin Whale
Order Cetacea : Family Balaenopteridae : Balaenoptera physalus (Linnaeus)

Description. A large, slender whale similar to the blue whale but head V-shaped in dorsal view, rather than U-shaped; dorsal fin high and placed even with or posterior to anus, on posterior one-fourth of body; pectoral fin about one-ninth of total length; head flattened, with right side more whitish than left; right lower jaw white, left grayish to black; upperparts gray, underparts pure white; grooves on throat numerous and extending beyond navel; whalebone lead color with whitish or yellowish fringes, 45-90 cm long, and more than 400 blades on each side. External measurements of an immature animal: total length, 18 m; tip of snout to corner of mouth, 3.6 m; expansion of flukes, 4.3 m. Old individuals attain a length of 25 m or more; females average slightly larger than males. Weight of a 21-m female, 59.4 metric tons.

Distribution in Texas. Cosmomarine, but rare in Texas waters. One young individual, 5.5 m long, was stranded on the beach at Gilchrist, Chambers County, on February 21, 1951. This is the only known Texas record. Fin whales are classified as "endangered."

Habits. Fin whales are highly migratory. The whales move to high latitude feeding grounds during spring and summer and return to southerly, temperate waters for mating and calving during autumn and winter. As with other migratory baleen whales, northern and southern hemisphere populations do not interbreed due to asynchronous seasons.

Fin whales feed mainly on krill but also eat schooling fish including herring, cod, mackerel, pollock, sardine, and capelin. Fish are eaten more often in winter.

The reproductive habits of these whales remain largely unknown; however, females are thought to give birth only at 3-year intervals. Mating and calving occur from November to March in temperate waters. The gestation period is approximately 11 months and newborn fin whales are about 6.4 m in length and weigh 1.8 metric tons. The period of lactation lasts 6-7 months and after weaning the young whales are approximately 12.2 m long. Sexual maturity is reached at 6-12 years of age.

Illustration credit: Pieter A. Folkens.