Blue Whale 5-Year Review
Final Recovery Plan for the Blue Whale
- Notice of availability of Draft Recovery Plan (83 FR 51665, 10/12/2018)
- Notice of Intent to Update the Blue Whale Recovery Plan (77 FR 22760, 04/17/201…
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Blue whales are the largest animals ever to live on our planet. They feed almost exclusively on krill, straining huge volumes of ocean water through their baleen plates (which hang from the roof of the mouth and work like a sieve). Some of the biggest individuals may eat up to 6 tons of krill a day.
Blue whales are found in all oceans except the Arctic Ocean. There are five currently recognized subspecies of blue whales.
The number of blue whales today is only a small fraction of what it was before modern commercial whaling significantly reduced their numbers during the early 1900s, but populations are increasing globally. The primary threats blue whales currently face are vessel strikes and entanglements in fishing gear.
NOAA Fisheries and its partners are dedicated to conserving and rebuilding blue whale populations worldwide. We use a variety of innovative techniques to study, protect, and rescue these endangered animals. 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.
Blue whales were significantly depleted by commercial whaling activities worldwide. Today, blue whales are listed as endangered under the Endangered Species Act and protected under the Marine Mammal Protection Act. The latest stock assessment reports of blue whales include data for various stocks, including areas of the North Pacific and western North Atlantic Oceans.
Blue whales have a long body and generally slender shape. Their mottled blue-gray color appears light blue under water—hence their name, the blue whale. The mottling pattern is variable and can be used to identify individuals.
Antarctic blue whales are generally larger than other blue whale subspecies. For example, in the North Atlantic and North Pacific, blue whales can grow up to about 90 feet and are over 100,000 pounds, but in the Antarctic, they can reach up to about 110 feet and weigh more than 330,000 pounds. Like many other baleen whales, female blue whales are generally larger than males.
Blue whales sometimes swim in small groups but are more often found alone or in pairs. They generally spend summers feeding in polar waters and undertake lengthy migrations towards the equatorial waters as winter arrives.
Blue whales typically swim at about 5 miles an hour while they are feeding and traveling, but can accelerate to more than 20 miles an hour for short bursts. They are among the loudest animals on the planet, emitting a series of pulses, groans, and moans, and it is thought that in the right oceanographic conditions, sounds emitted by blue whales can be heard by other whales up to 1,000 miles away. Scientists think they use these vocalizations to communicate and—along with their excellent hearing—perhaps to sonar-navigate the dark ocean depths.
The primary diet of blue whales is krill—tiny shrimp-like animals, but fish and copepods (tiny crustaceans) may occasionally be part of the blue whale’s diet. When blue whales hunt for food, they filter feed by swimming toward large schools of krill with their mouth open and closing their mouths around the krill while inflating their throat pleats. Once closed, blue whales then push the trapped water out of their mouth with their tongue and use their baleen plates to keep the krill trapped inside.
Blue whales are found in all oceans except the Arctic. They generally migrate seasonally between summer feeding grounds and winter breeding grounds, but some evidence suggests that individuals in certain areas might not migrate at all. Information about distribution and movement varies with location, and migratory routes are not well known. In general, distribution is driven largely by food availability—they occur in waters where krill are concentrated.
In the North Atlantic Ocean, their range extends from the subtropics to the Greenland Sea. Blue whales have been sighted in the waters off eastern Canada and in the shelf waters of the eastern United States.
Along the West Coast of the United States, eastern North Pacific blue whales are believed to spend winters off of Mexico and Central America. They likely feed during summer off the U.S. West Coast and, to a lesser extent, in the Gulf of Alaska and central North Pacific waters.
Blue whales with young calves are regularly observed in the Gulf of California (Sea of Cortez) from December through March. It is believed that this area is an important calving and nursing area for the species.
In the northern Indian Ocean, there is a "resident" population. Blue whale sightings, strandings, and acoustic detections have been reported from the Gulf of Aden, Arabian Sea, and across the Bay of Bengal. The migratory movements of these whales are largely unknown but may be driven by oceanographic changes associated with monsoons.
In the Southern Hemisphere, Antarctic blue whales occur mainly in relatively high latitude waters south of the "Antarctic Convergence" and close to the ice edge in summer. They generally migrate to middle and low latitudes in winter, although not all whales migrate each year. Pygmy blue whales (Balaenoptera musculus brevicauda)—a subspecies—are typically distributed north of the Antarctic Convergence and are most abundant in waters off Australia, Madagascar, and New Zealand. An unnamed subspecies of blue whale is found in the southeastern Pacific Ocean, particularly in the Chiloense Ecoregion, and migrates to lower latitude areas, including the Galapagos Islands and the eastern tropical Pacific.
Blue whales’ average lifespan is estimated at around 80 to 90 years. Scientists can estimate the age of whales by counting the layers of wax-like earplugs collected from deceased animals.
Scientists know little about the life history of the blue whale. The best available science suggests the gestation period is approximately 10 to 12 months. Weaning probably occurs at around 6 to 7 months on, or en route to, summer feeding areas. The age of sexual maturity is thought to be 5 to 15 years. Most reproductive activity, including births and mating, takes place during the winter. The average calving interval is probably 2 to 3 years.
Vessel strikes can injure or kill blue whales. Vessel strikes have killed blue whales throughout their range, but the risk is much higher in some coastal areas with heavy vessel traffic, like ports and in shipping lanes, and from larger vessels and vessels traveling at high speeds.
Blue whales can become entangled in fishing gear, either swimming off with the gear attached or becoming anchored. Blue whales can become entangled in many different gear types, including traps, pots, and nets. Once entangled, whales may drag the attached gear for long distances, ultimately resulting in fatigue, compromised feeding ability, or severe injury, which may lead to reduced reproductive success and death.
Additional possible threats to blue whales that are less understood include ocean noise, habitat degradation, pollution, vessel disturbance, and climate change.
All blue whales are protected under the MMPA and ESA. Our work strives to protect blue whales by:
Our research projects have helped us better understand blue whales and the challenges they face. Our work includes:
Blue whales are protected under both the Endangered Species Act and the Marine Mammal Protection Act. NOAA Fisheries is working to protect this species in many ways.
Under the ESA, NOAA Fisheries is required to develop and implement recovery plans for the conservation and survival of listed species. The ultimate goal of the Blue Whale Recovery Plan is to recover the species, with an interim goal of downlisting its status from endangered to threatened. This consists of six objectives:
A primary strategy of the Recovery Plan, revised in 2020, is to maintain the international ban on commercial hunting that was instituted in 1986. Additionally, this Plan provides a strategy to improve our understanding of how potential threats may be limiting blue whale recovery. Finally, this plan provides a research strategy to obtain data necessary to determine blue whale taxonomy, population structure, distribution, and habitat, which can then inform estimation of population abundance and trends. Once the populations and their threats are more fully understood, this plan will be modified to include actions to minimize any threats determined to be limiting recovery. Because blue whales move freely across international borders, recovery efforts are not confined to U.S. waters. Thus, this plan stresses the importance of a multinational approach to management.
Collisions between whales and vessels can injure or kill the whales and damage the vessels, but they often go unnoticed and unreported. NOAA Fisheries has taken both regulatory and non-regulatory steps to reduce the threat of vessel collisions with whales. Precautions that vessel operators can take include:
Learn when the seasonal abundance of large whales are in shipping lanes; listen and be aware of advisories
Consult the United States Coast Guard’s “Local Notice to Mariners” or the “Coast Pilot,” which supplements the navigational information shown on NOAA nautical charts, for more information
Keep a sharp lookout for whales, including posting additional crew lookouts on the bow, if possible
Reduce speeds while in advisory zones or in areas of high seasonal or local whale abundance
If practicable, re-route vessels to avoid areas of high whale abundance
The most effective way to reduce collision risk is to keep whales and vessels separated by great distances; where this is not possible, vessels need to slow down and keep a lookout.
Learn more vessel strikes and marine mammals
We work with volunteer networks in all coastal states to respond to marine mammal strandings including all whales. When stranded animals are found alive, NOAA Fisheries and our partners assess the animal’s health and determine the best course of action. When stranded animals are found dead, our scientists work to understand and investigate the cause of death. Although the cause often remains unknown, scientists can sometimes attribute strandings to disease, harmful algal blooms, vessel strikes, fishing gear entanglements, pollution exposure, and underwater noise. Some strandings can serve as indicators of ocean health, giving insight into larger environmental issues that may also have implications for human health and welfare.
Learn more about the Marine Mammal Health and Stranding Response Program
Blue whales have been part of a declared unusual mortality event in the past. Under the Marine Mammal Protection Act, an unusual mortality event is defined as "a stranding that is unexpected; involves a significant die-off of any marine mammal population; and demands immediate response." To understand the health of marine mammal populations, scientists study unusual mortality events.
Get information on active and past UMEs
Get an overview of marine mammal UMEs
Noise pollution can threaten whale populations, interrupting their normal behavior and driving them away from areas important to their survival. NOAA Fisheries is investigating all aspects of acoustic communication and hearing in marine animals, as well as the effects of sound on whale behavior and hearing. In 2018, NOAA Fisheries issued revised technical guidance for assessing the effects of anthropogenic sound on marine mammals’ hearing.
The blue whale is listed as endangered throughout its range under the ESA and is thus considered depleted throughout its range under the MMPA.
Internationally, blue whales received complete legal protection from commercial whaling in 1966 under the International Convention for the Regulation of Whaling.
NOAA Fisheries conducts various research activities on the biology, behavior, and ecology of blue whales. The results of this research are used to inform management decisions and enhance recovery efforts for this endangered species.
Scientists working on the WhaleWatch project are using advanced technologies to predict where blue whales are likely to be in near real-time off the U.S. West Coast. This near real-time information helps reduce human effects on whales by providing information on where the whales occur and hence where whales may be most at risk from threats such as vessel strikes, entanglements, and underwater noise. Scientists developed habitat-based model estimates of whale occurrence that combine satellite tracking of whales with information on the environment.
Learn more about the WhaleWatch project
Determining the size of the blue whale population—and whether it is increasing or decreasing—helps resource managers assess the success of the conservation measures enacted. NOAA Fisheries scientists collect population information on blue whales from various sources and present these data in annual stock assessment reports.
NOAA Fisheries’ research surveys investigate blue whales’ habitat preferences and feeding ecology and collect photographs and genetic samples. Information from this research is used in management actions that protect the blue whale and reduce human-related deaths.
Other research is focused on the acoustic environment of blue whales. This research involves:
Endangered Species Act Recovery Plan for the Blue Whale (Balaenoptera musculus)
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