Sleek and fast, the name (pronounced “sigh”) derives from the Norwegian word for pollack because of the appearance of pollack off the Norwegian coast sometimes coincides with the arrival of sei whales. Sei whales are widely found near the Antarctic up to Iceland in the North Atlantic. However, they are somewhat more common in colder waters and show a seasonal migration pattern.
Dark gray and streamlined, the sei whale has a tall sickle shaped dorsal fin. They are often white or cream-colored on the underside and have thirty to sixty throat grooves. The pectoral fins are short and pointed; the flukes are also short in relation to the body length. Their baleen plates, numbering three hundred to four hundred ten on each side of the mouth, are black outside with a white fringe that is very fine and silky. Females are slightly longer than males as with all baleen whales, measuring about fifty feet. Full-grown adults weigh approximately twenty to thirty tons. The dive of a sei is different to other whales; they simply sink below leaving smooth circles on the surface.
A male sei whale reaches maturity at a length of forty feet, females at fifty feet. Calving is once every two years with gestation of about a year. At birth the calf is fourteen to fifteen feet long and about two thousand pounds. A sei calf will nurse for up to nine months Together with the fin whale, seis are probably the fastest of the large whales, achieving up to twenty-five knots over a short distance. They are usually solitary animals, found in groups of two and three or sometimes a good food spot will attract a large group of up to one hundred. Although the feeding grounds are defined, little is known about the mating and breeding of these whales.
Although the fine baleen is suited for its favorite food, copepods they frequently eat fish and krill. Due to the food location, sei whales spend periods at the surface. With mouths open they skim the surface for food, giving a tall columnar blow, once every ninety to one hundred twenty seconds. It is the only mysticete that feeds both by gulping and skimming.
As hunting depleted other species of whales, whalers turned to the sei even though it is slim and has little blubber. A population crash followed creating the classification as endangered species today. Estimates in United States waters is unknown, worldwide it is believed there are fifty-four thousand sei whales.