Distribution
Baleen whales can be found in all oceans worldwide, from polar seas to temperate and tropical zones.
Some species of baleen whales have limited distribution. For example:
- Southern right whales (Eubalaena australis) are found only in the southern hemisphere; northern right whales (Eubalaena glacialis) are found only in the northern hemisphere.
- Bowhead whales (Balaena mysticetus) inhabit the waters around the Arctic ice edges that melt and reform seasonally.
- Some populations of baleen whale species are resident to restricted areas. A population of fin whales (Balaenoptera physalus) is found year-round in the Gulf of California
Some species are found throughout the world. For example, fin whales, minke whales (Balaenoptera acutorostrata), sei whales (Balaenoptera borealis), blue whales (Balaenoptera musculus), and humpback whales (Megaptera novaeangliae) have worldwide distributions. Bryde's whales (Balaenoptera edeni) are found throughout the tropics and subtropics.
Habitat
Some baleen whales are coastal (they stay near shore). They forage along the productive continental shelf area. Some species give birth and rear young in protected coastal bays and lagoons. Other species are oceanic (they roam the open seas).
Migration
Most baleen whales are highly migratory, moving toward high-latitude (polar) feeding areas in the summer and toward low-latitude (tropical) calving areas in the winter.
- Variations in water temperature, food availability, and feeding habits may account for movements of some animals.
- Some individual whales do not migrate. These may be juveniles or post-reproductive adults and may stay in protected nearshore areas.
Northern and southern hemisphere populations of the same species don't encounter one another due to the opposite seasons in the northern and southern hemisphere. While the northern population is breeding and calving in tropical regions during the northern hemisphere's winter, the southern population is foraging in polar feeding grounds during the southern hemisphere's summer.
Many factors may act as environmental cues to help baleen whales navigate along a migration route: sun orientation, topography of the ocean floor, water temperature, chemical changes in the water, and magnetic sensing. Satellite-tracking studies assist scientists researching migratory behavior of baleen whales.
Most baleen whales migrate 3,000–5,000 km (1,800–3,000 mi.) each way, depending on the species.
- Gray whales migrate more than 10,000 km (6,000 mi.) each way – the longest known migration for any mammal.
- Some species migrate much shorter distances. For example, Bryde's whales only move from temperate regions to the equator. And sei whales don't migrate as far toward the poles as most species do.
Population
For most baleen whale species, estimating abundance is difficult due to their vast distribution and their aquatic habits.
For many species, there are no population estimates. For others, estimates are based on old data that may no longer reflect the current population. The table below lists the most current estimates available
As a management tool, scientists categorize a geographically isolated and genetically distinct group of whales as a whale stock. Thus, a species may be represented by several stocks. For some species, certain stocks are depleted, while worldwide population numbers remain high.
- More than 800,000 minke whales are found worldwide, yet scientists consider the West Greenland stock depleted.
- Most of the total current population of bowhead whales survives in only one of five stocks. The other four face extinction.
- Certain stocks are recovering due to international protection from commercial whaling. Most notably, the gray whale population appears to have reached pre-whaling numbers.
- Photo-identification of individual whales helps researchers monitor the size of certain populations. Experts photograph and catalog scars and other natural markings on the flukes, dorsal fins, and flanks of individual whales. When these identified whales are re-sighted during subsequent years, researchers can gather information on reproductive and growth rates, differences between males and females, and migration.
Baleen Whale Distribution & Abundance
Family Balaenidae: The Right Whales
| Species | Distribution | Abundance |
| bowhead whale (Balaena mysticetus) |
Bering-Chukchi-Beaufort Seas Sea of Okhotsk Davis Strait Hudson Bay Greenland Sea |
8,000 probably 10s to a few 100s in each of these populations |
| pygmy right whale (Caperea marginata) |
- | - |
| Southern right whale (Eubalaena australis) |
- | - |
| Northern right whale (Eubalaena glacialis) |
- | - |
Family Balaenopteridae: The Rorqual Whales
| Species | Distribution | Abundance |
| minke whale (Balaenoptera acutorostrata) |
southern hemisphere North Atlantic western North Pacific rest of North Pacific |
761,000 149,000 25,000 unknown |
| sei whale (Balaenoptera borealis) |
southern hemisphere North Pacific North Atlantic |
37,000 14,000 probably few 1,000s |
| Bryde's whale (Balaenoptera edeni) |
western North Pacific rest of northern hemisphere southern hemisphere |
14,000 unknown unknown |
| blue whale (Balaenoptera musculus) |
southern hemisphere California, Oregon, Washington rest of northern hemisphere |
400-1,400 1,480 unknown |
| fin whale (Balaenoptera physalus) |
North Atlantic California, Oregon, Washington rest of northern hemisphere southern hemisphere |
47,300 3,200 unknown 103,000 |
| humpback whale (Megaptera novaeangliae) |
western North Atlantic rest of northern hemisphere southern hemisphere south of 60˚S rest of southern hemisphere |
11,570 unknown 10,000 unknown |
Family Eschrichtidae: The Gray Whale
| Species | Distribution | Abundance |
| gray whale (Eschrichtius robustus) |
eastern North Pacific western North Pacific |
26,000 less than 100 |