About animals

Balaenoptera borealis Lesson, 1828 - morfil asgellog sei


  • Habitat - open water.
  • Status - occurs everywhere.
  • Number of groups - 2-5 (1-5) largest groups, up to 30, in food places.
  • Dorsal fin location - far beyond the center
  • Newborn weight - 725 kg.
  • Adult weight - 20-30 tons.
  • Newborn length - 4.4-4.8 m.
  • Adult length - 12-16 m.
  • Nutrition - in the North Atlantic, the whale eats various species of copepods and euphasiacephalan, in the seas of the Far East, in addition, fish (saury, Pacific sardine, smelt, gerbil, pollock, capelin, navaga, mackerel, sea lenok, herring, pollock, sea ruff) , and the Kuril ridge and Japan also cephalopods. In the Southern Hemisphere, the menu includes more than fifty species of crustaceans, up to one and a half dozen species of fish and more than a dozen species of winged and cephalopod mollusks. In Antarctica, the main feed of the seyvail is the same as that of all baleen whales - the euphasian black-eye crustacean.

Latin name borealis means "northern" (northern). Other names: Sei whale, pollack whale, coal fish whale, sardine whale, Japan finner, rorqual de Rudolphi (Fr), seiwal (Ger), noordse vinvis (NL), sejhval (Dan), sejval (Swe), seihval (Nor ), balenottera boreale (It), ballena boba, rorcual norteno (Sp), baleia-sardinheira (Por), iwashi kujira (Jap), seival (Rus). The third largest minke whale. Another name is the side-whale.

The seyval plunges downward, slightly bending, so the edge of its caudal stem either does not show up at all from the water, or is set low and does not form a semicircle. The number of fountains is irregular - from 1 to 5, with pauses between them from 4 to 22 s, with a height of 2-5 m. Diving lasts from half a minute to 12 minutes. The highest speed of movement for the wounded with tags at the first moment reaches 40-50 km / h, for those grazing decreases to 5 km / h. The beast usually swims shallowly, and then whirlpools caused by the operation of the tail lobes are noticeable on the surface.
Ectoparasites are the same as in the first two species of minke whales.

Sayvale is as widespread as finwal, but usually avoids ice in the Arctic and Antarctic, appears there later than large species of minke whales, and is less regular in migration. In the Northern Hemisphere, it penetrates to the Strait of Davis, Spitsbergen, Novaya Zemlya, Alaska, the Sea of ​​Okhotsk, Kamchatka and very rarely to the Chukchi Sea. In the equatorial belt appears only in winter in small quantities. It is more numerous in the waters of Japan, near the southern part of the Kuril ridge, near the island of South Georgia and the shores of South Africa. Off the Pacific coast of North America, it runs from Alaska to Mexico. In the North Atlantic, he often visits the waters of Norway, the Hebrides and Orkney Islands, less often the Barents and White Seas, and in the Baltic Sea saiv is very rare.

Seival pregnancy lasts about a year, mating is extended for six months, with a peak in the middle of winter. The baby is born 4.5 m long, is fed milk for 5-6 months and during this period grows to 8-9 m.

Compared to the finwail, the seyval is less built, its body is relatively thicker, the pectoral fins are shorter, and the dorsal fin is more and more advanced forward to the beginning of the posterior third of the animal. The color of the back is dark gray, slightly lighter on the sides, and on the abdomen unstable, varies from gray to partially white (but the entire bottom is usually white). The recesses of the bands are dark, gray or light. On the sides, especially on the caudal stem, less often on the back, there are small light numerous spots - traces of the activity of ectoparasites and microorganisms. The dorsal fin and tail lobes are on top the same color as the back, and the pectoral fins on top are the same as the sides of the body, below the caudal fins and pectoral fins are paler and usually gray.
The head is about 1/4 of the body length, and in young women it is less than in old ones, and in females less than in males. The sky is narrow, white or pink. On the belly 40-64 stripes, the longest of them end without reaching the navel. Long and narrow nasal bones formed in the skull.

  • longitudinal protrusion on the head
  • high crescent dorsal fin
  • caudal stem not convex
  • rarely shows caudal fin
  • both sides of the head are equally dark
  • relatively low fountain
  • breathing and dorsal fin showing simultaneously
  • often swims close to the surface of the water

On the sides of the sky are 300-400 whisker plates with a thin, hairy curly gray fringe. The plates are black-gray, but several dozen front ones are white, the highest up to 80 cm. The plates grow from the base at 6-9 cm per year.

References: “Animal Life”, vol. 7 / Mammals / –– Edited by V.E. Sokolov. - 2nd ed., Revised.-M .: Education, 1989 - 558 p., Sokolov V. E. Rare and endangered animals. Mammals: Handbook.-M.: Higher school, 1986.-519 S.I.

Bern Convention Appendix 2: Current

Special protection (`appropriate and necessary legislative and administrative measures`) for the animal taxa listed, including all forms of deliberate capture and keeping and deliberate killing, the deliberate damage to or destruction of breeding or resting sites, the deliberate disturbance of wild fauna, particularly during the period of breeding, rearing and hibernation, insofar as disturbance would be significant in relation to the objectives of this Convention, the deliberate destruction or taking of eggs from the wild or keeping these eggs even if empty, the possession of and internal trade in these animals, alive or dead, including stuffed animals and any readily recognizable part or derivative therefore, where this would contribute to the effectiveness of the provisions of this article.

Habitats Directive Annex 4: Current

Animal and plant species of Community interest (i.e. endangered, vulnerable, rare or endemic in the European Community) in need of strict protection. They are protected from killing, disturbance or the destruction of them or their habitat. Note that the contents of this annex have been updated in April 2003 following the Treaty of Accession.

Priority Species (Northern Ireland): Current

The Northern Ireland Priority List of threatened species requiring conservation action in Northern Ireland. Criteria have been developed to ensure that Priority Species have been chosen using a scientific basis (See http - // www.habitas.org.uk/priority/criteria.html). The list is designed to assist those involved in the conservation of biodiversity by guiding decisions on where to target action and invest resources.

About The Species

Sei whales occur in subtropical, temperate, and subpolar waters around the world. Often found with pollack in Norway, the name "sei" comes from the Norwegian word for pollack, "seje."

The sei whale population has been greatly decreased by commercial whaling. During the 19th and 20th centuries, sei whales were targeted and greatly depleted by commercial hunting and whaling, with an estimated 300,000 animals killed for their meat and oil.

Commercial whaling ended for this species in 1980. Although whaling is no longer a major threat to this species, some scientific whaling continues today in Iceland and Japan. Vessel strikes and entanglement pose the biggest threat to sei whales today. The sei whale is listed as endangered under the Endangered Species Act and depleted under the Marine Mammal Protection Act.

NOAA Fisheries and our partners are dedicated to conserving and rebuilding the sei whale population. We use a variety of innovative techniques to study, protect, and rescue these endangered whales. We engage our partners as we develop regulations and management plans that foster healthy fisheries and reduce the risk of entanglements, create whale-safe shipping practices, and reduce ocean noise.


Today, there are around 8,600 sei whales in the North Pacific. This is only little more than 20 percent of the original population estimate of 42,000 for this area.

The total population of sei whales in all U.S. waters is unknown.

The most recent population assessments can be found on the sei whale stock assessment reports.


Sei whales have a long, sleek body that is dark bluish-gray to black in color and white or cream-colored on the underside. The body is often covered in oval-shaped scars (probably caused from cookie-cutter shark and lamprey bites) and sometimes has subtle "mottling," or discolored spots or blotches.

Sei whales have a tall, hooked dorsal fin located about two-thirds down their back. Sei whales have 219 to 410 baleen plates (long, finger-nail like plates instead of teeth) that are dark in color with gray / white fine inner fringes in their enormous mouths. They also have 30-65 relatively short accordion-like creases, or throat grooves, that extend from below the mouth to the naval area. The number of throat grooves and baleen plates may differ depending on geographic population.

At the water's surface, sei whales can be sighted by a columnar or bushy blow that is about 10 to 13 feet in height. The dorsal fin usually appears at the same time as the blowhole when the animal surfaces to breathe.

Behavior and diet

Sei whales are usually observed alone or in small groups of two to five animals. They are fast swimmers that can reach speeds of over 34 miles per hour.

Sei whales dive differently than most whales. They do not arch their backs or show their flukes before diving, they simply sink below the surface. They often leave “fluke prints” —smooth circles on the surface created by the movement of the fluke underwater.

An average sei whale eats about 2,000 pounds of food per day. They can dive 5 to 20 minutes to feed on plankton (including copepods and krill), small schooling fish, and cephalopods (including squid) by both gulping and skimming. They prefer to feed at dawn and may exhibit unpredictable behavior while foraging and feeding on prey.

Where they live

Sei whales have a wide distribution and live in subtropical, temperate, and subpolar waters around the world. They prefer temperate waters in the mid-latitudes, and can be found in the Atlantic, Indian, and Pacific Oceans. During the summer, they are commonly found in the Gulf of Maine, and on Georges Bank and Stellwagen Bank off the U.S. coast in the western North Atlantic. The movement patterns of sei whales are not well known, but they are typically observed in deeper waters far from the coastline. Sei whales have an unpredictable distribution. Many whales may be found in one area for a period and then not return for years or decades. This behavior is unusual for large whales, who generally have a predictable distribution. No one knows where sei whales breed.

Lifespan & Reproduction

Sei whales become sexually mature at 6 to 12 years of age when they reach about 45 feet in length. They generally mate and give birth during the winter in lower latitudes.

Females breed every 2 to 3 years, with a gestation period of 11 to 13 months. Calves are about 15 feet long and weigh about 1,500 pounds at birth. Mothers burse their calves for 6 to 9 months before weaning them when at their preferred feeding grounds.


One of the main threats to sei whales is getting caught in fishing gear. They can become entangled gear including traps, pots, and gillnets. Once entangled, whales may swim for long distances with gear attached, resulting in fatigue, compromised feeding ability, or severe injury. These conditions can lead to reduced reproductive success and death.

Conservation & Management

NOAA Fisheries is committed to the protection and recovery of sei whales. Targeted management actions taken to protect these whales include:

  • Minimizing the effects of noise disturbance.
  • Responding to stranded sei whales.
  • Developing oil spill response plans.
  • Reviewing projects that could harm sei whales.
  • Educating the public about sei whales and the threats they face.
  • Monitoring population abundance and distribution.
Learn more about our conservation efforts


Our research projects have discovered new aspects of sei whale biology, behavior, and ecology, and helped us better understand the challenges that all sei whales face. This research is especially important in rebuilding endangered populations. Our work includes:

  • Stock assessments.
  • Measuring sei whales response to sound.
Learn more about our research