CONSERVATION

DISTRIBUTION

The blue whale is found from the tropics to the drift ice of polar waters, occupying the Arctic, Atlantic, Indian and Pacific Oceans. Despite their wide distribution, blue whales are not often encountered. While this in part is due to their reduced numbers, it is mostly due to the fact that they generally occur in offshore waters, with only a few known coastal breeding and feeding areas.

In Figure 6, we can see that blue whales travel between their feeding and breeding areas. When the temperature drops, they migrate to warmer waters and begin mating. During this migration, blue whales swim slowly in order to conserve energy.

Figure 6. Blue Whale Migratory Map

Figure 7. Blue Whale Distribution Map

As of 2018, the global blue whale population size is estimated to be between 5,000 – 15,000 mature individuals and 10,000 - 25,000 total. The estimated total number of blue whales in occupying the North Atlantic is 1,000 - 3,000; 3,000 - 5,000 in the North Pacific; 5,000 - 8,000 in the Antarctic; and potentially 1,000 - 3,000 blue whales in the eastern South Pacific. The pygmy blue whale is estimated between 2,000 - 5,000 individuals.

By comparison, there were roughly 140,000 mature whales in 1926.

POPULATION

Figure 8. Blue Whale Population Trend, British Sea Fishing

At one point, blue whales were abundant in nearly all of Earth's oceans. Unfortunately, at the end of the 19th century they were nearly hunted into extinction. It wasn’t until the International Whaling Commission banned all blue whale hunting in 1966, that the species' substantial death rate began to subside. While the population of Balaenoptera musculus has made a slight recovery over the last several decades, for populations like the Pygmy blue whale, there is not enough information on current abundance trends; and others like the Antarctic blue whale are considered critically endangered.

PROTECTION

Blue whales are formally classified as endangered under both the US Endangered Species Act and the IUCN Red List. They are also listed on Appendix I under the Convention on International Trade in Endangered Species of Wild Fauna and Flora and the Convention on the Conservation of Migratory Species of Wild Animals.

Despite gaining protection from commercial hunting by the International Whaling Commission, illegal catches by USSR fleets continued until 1972. Currently, whaling is illegal in most countries, however Iceland, Norway, and Japan still actively engage in whaling. Over a thousand whales are killed each year for commercial gain.

The IWC recognizes three types of whaling: aboriginal subsistence whaling to support the needs of indigenous communities, commercial whaling that has been subject to a moratorium since 1986, and scientific whaling in which countries are asked to submit special permit research proposals to the IWC for scientific scrutiny.

Figure 9. Blue Whale Protection Areas

ONGOING THREATS

For decades, the International Union for Conservation of Nature has listed blue whales as endangered, with the most recent update in 2018. The species continues to face numerous man-made threats such as ship strikes, pollution, ocean noise, and climate change.

Recently, a male blue whale was killed from a collision with a ship off the coast of California. After the whale was brought onto shore, researchers performed an analysis which revealed contaminants such as pesticides, flame retardants, and mercury were present in the animals earwax.

Blue whales are considered a conservation-reliant species. This term is recognized as an animal or plant species that require continuing species-specific wildlife management intervention. This intervention can be in the form of predator control, habitat management, or even parasite control to survive, even when a self-sustainable recovery in population is achieved.

Ship strikes are a continuous mortality factor for blue whales. In the western coast of the U.S. alone, 17 blue whales have been killed by ships between 1998 and 2019.

CONSERVATION ACTIONS

SATELLITE TRACKING

WWF is using satellite tags to see what specific routes are used by the whales and which areas are used the most often. This information will help inform decisions about protected areas, to prevent interactions between whales and salmon farms or wild-caught fisheries.

MARK AND RECAPTURE

Mark and recapture is a method used to determine the population size of blue whales; specifically Antarctic blue whales as there population size has been nearly decimated due to environmental disturbance.

ORGANIZED SUPPORT

Alongside governmental protection, organizations such as The Center for Biological Diversity work to analyze data about species status and recovery, obtain critical habitat for species, and take multiple actions to ensure that imperiled species are federally protected.

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