Balaenoptera borealis, commonly known as the sei whale, inhabits deep ocean waters worldwide, favoring temperate and subtropical regions. It is known for its long, streamlined body, reaching up to 20 meters, and its unique feeding method, gulping large volumes of water and filtering prey through baleen plates. Sei whales are among the fastest of the great whales, capable of reaching speeds up to 50 km/h. They primarily feed on small fish, squid, and zooplankton.

Balaenoptera borealis, commonly known as the Sei Whale, is found in all of the world's oceans and adjoining seas, except in tropical and polar regions. It is most commonly observed in the North Atlantic and North Pacific Oceans, as well as in the Southern Hemisphere between 20° and 60° latitude.

Sei Whales inhabit deep off-shore waters and are typically found in areas with temperate and subtropical climates. They prefer oceanic waters with temperatures ranging from 8°C to 25°C. These whales often migrate between feeding grounds in higher latitudes during summer months and warmer waters during winter for breeding.

As a baleen whale, the Sei Whale primarily feeds on small schooling fish, crustaceans, and plankton, often found in large concentrations. They play a crucial role in the marine ecosystem as predators of these small organisms and as prey for larger marine predators. Their feeding behavior often involves skimming the water surface or engulfing large volumes of water, filtering their food through baleen plates.