Whales and New Jersey: Sei Whales

Sei whale and calf

In this last post about whales that travel off the New Jersey coastline and that are federally endangered (and so protected while in our waters), we look at the sei whale.

Sei whales reach lengths of 18.9 meters (62 ft.). They have dark steel-gray body frequently looks galvanized. The body is frequently covered with small pit-like circular scars, which come from the bites of cookie-cutter sharks.

Sei is the Norwegian word for pollock, also referred to as coalfish, a close relative of codfish. Sei whales appeared off the coast of Norway at the same time as the pollock, both coming to feed on the abundant plankton. The specific name is the Latin word borealis, meaning northern.

The development of explosive harpoons and steam-powered whaling ships in the late nineteenth century brought previously unobtainable large whales like the Sei within reach of commercial whalers. Initially their speed and elusiveness, and later the comparatively small yield of oil and meat partially protected them. But once stocks of more profitable right whales, blue whales, fin whales, and humpback whales became depleted, sei whales were hunted in earnest, particularly from 1950 to 1980.

The right lower lip is gray and baleen plates are primarily grayish black. The whale's snout is barely arched, while its slightly pointed rostrum (the forward extension of the upper jaw) sports a single median dorsal ridge. Two-thirds of the body length back of the head is a tall curved, tall dorsal fin. The leading edges of the flukes are occasionally white.

When the sei whale spouts a blow it can be either bushy or columnar and it is usually quite tall.

The sei whale is a baleen whale, and the third-largest rorqual baleen whale after the blue whale and the fin whale.

It inhabits most oceans and adjoining seas, and prefers deep offshore waters. It avoids polar and tropical waters and semi-enclosed bodies of water.

The sei whale migrates annually from cool and subpolar waters in summer to winter in temperate and subtropical waters.

Sei whales have a lifespan of 70 years.

The total number of sei whales in U.S. waters is unknown. A old tag-and-recapture study from 1977 estimated the stock ranged between nearly 1,400 and 2,250 sei whales.

Mass death events for sei whales have been recorded for many years and evidence suggests endemic poisoning ("marea roja") causes may have caused mass deaths in prehistoric times.

In June 2015, scientists flying over southern Chile counted 337 dead sei whales, in what is regarded as the largest mass beaching ever documented. The cause is not yet known; however, toxic algae blooms caused by unprecedented warming in the Pacific Ocean, known as the Blob, may be implicated.

Whale, North Atlantic right**	Eubalaena glacialis**
Whale, blue**	Balaenoptera musculus**
Whale, fin**	Balaenoptera physalus**
Whale, humpback**	Megaptera novaeangliae**
Whale, sei**	Balaenoptera borealis**
Whale,sperm**	Physeter macrocephalus**
**Federally Endangered