- 1998 Take Reduction Plan (Final Rule)
- 2010 Amended Take Reduction Plan (Final Rule)
- 2013 Amended Take Reduction Plan (Final Rule)
About the Species
The harbor porpoise is a shy animal, most often seen in groups of two or three. They prefer coastal areas and are most commonly found in bays, estuaries, harbors, and fjords. Because they prefer coastal habitats, harbor porpoises are particularly vulnerable to gillnets and fishing traps, pollution, and other types of human disturbance, such as underwater noise.
Harbor porpoises in the United States are not endangered or threatened. Like all marine mammals, they are protected under the Marine Mammal Protection Act.
NOAA Fisheries helps conserve the harbor porpoise through collaborative management, integrated science, partnerships, and outreach. Our scientists use a variety of innovative techniques to study, protect, and rescue harbor porpoises in distress (e.g., disentanglement and stranding response). Our work helps reduce harmful effects of human activities such as fisheries interactions, noise, and pollution, through effective management actions based on sound science, public input, and public outreach.
NOAA Fisheries estimates population size for each stock of harbor porpoises in its stock assessment reports. A stock is a group of animals that occupy the same area and interbreed. Population trends for many of the U.S. stocks are unknown.
CITES Appendix II
- Throughout Its Range
- Throughout Its Range
Harbor porpoises have a small, robust body with a short, blunt beak and a medium-sized triangular dorsal fin. Their back is dark gray fading to lighter intermediate shades of gray on their sides. Their belly and throat are white, with a dark gray chin patch. Females are slightly larger than males.
Behavior and Diet
Harbor porpoises mainly eat schooling fish, like herring and mackerel. Occasionally, they will eat squid and octopus.
They are most often seen singly, in pairs, or in groups of up to 10, although there are reports of aggregations of up to 200 harbor porpoises. Most seasonal movements appear to be inshore-offshore and may be influenced by prey availability or the presence of ice-free waters.
Unlike most other porpoises, they do not approach boats to bow ride and can be very shy, avoiding surfacing near boats. When surfacing for air, they do not splash. They roll from beak to fluke and arch their backs.
Where They Live
Harbor porpoises live in northern temperate and subarctic, and arctic coastal and offshore waters. They are commonly found in bays, estuaries, harbors, and fjords less than 650 feet deep. In the North Atlantic, they range from West Greenland to Cape Hatteras, North Carolina (but do not enter Hudson Bay), and from the Barents Sea to West Africa. In the North Pacific, they are found from Japan north to the Chukchi Sea and from Point Conception off Central, California North to the Beaufort Sea.
Lifespan & Reproduction
Females reach sexual maturity at 3 to 4 years and may give birth every year for several years in a row. Gestation lasts for 10 to 11 months and lactation lasts for 8 to 12 months.
Little is known of their reproductive biology. Most mating occurs in summer and most births occur between May and July.
One of the main threats to harbor porpoises is getting caught in fishing gear. They can become entangled or captured in commercial fishing gear such as gillnets, trawls, and herring weirs.
Underwater noise pollution interrupts the normal behavior of harbor porpoises and interferes with their communication.
In the Spotlight
Like all marine mammals, the harbor porpoise is protected under the Marine Mammal Protection Act. NOAA Fisheries is working to conserve this species to ensure populations remain stable.
Reducing Interactions with Fishing Gear
Bycatch in fishing gear is a leading cause of harbor porpoise deaths and injuries. To reduce deaths and serious injuries of harbor porpoises from gillnet fisheries, NOAA Fisheries implemented the Harbor Porpoise Take Reduction Team.
Representatives from NOAA, the fishing industry, regional fishery management councils, state and federal resource management agencies, the scientific community, and conservation organizations worked together to develop a plan to reduce harbor porpoise bycatch. The plan includes regulations, such as seasonal gillnet restrictions, closures, and the use of acoustic deterrent devices called pingers. The group that developed the Harbor Porpoise Take Reduction Plan continues to meet to monitor the progress of the take reduction plans in achieving the MMPA long-term goal of reducing harbor porpoise bycatch to a zero mortality and serious injury rate.
Addressing Ocean Noise
Sound pollution threatens harbor porpoise populations by interrupting their normal behavior and driving them away from areas important to their survival. Increasing evidence suggests that exposure to intense underwater sound in some settings may cause some porpoises to strand and ultimately die. NOAA Fisheries is investigating all aspects of acoustic communication and hearing in marine animals. In 2018, we revised technical guidance for assessing the effects of anthropogenic sound on marine mammal hearing.
Overseeing Marine Mammal Health and Stranding Response
We work with volunteer networks in all coastal states to respond to marine mammal strandings including all dolphins and porpoises. 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.
Marine Mammal Unusual Mortality Events
Harbor porpoise 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.
Harbor porpoises are protected under the Marine Mammal Protection Act of 1972, as amended.
Key Actions and Documents
Incidental Take Authorization: Maine Department of Transportation Falls Bridge Project in Blue Hill, Maine
Incidental Take Authorization: Chesapeake Tunnel Joint Venture Parallel Thimble Shoal Tunnel Project in Virginia Beach, Virginia (2021)
Incidental Take Authorization: Alaska Department of Transportation Metlakatla Seaplane Facility Refurbishment Project, Metlakatla, Alaska
NOAA Fisheries conducts research on harbor porpoise biology, behavior, and ecology. This research informs management decisions and enhances conservation efforts.
Determining the number of harbor porpoises in each population—and whether a population is increasing or decreasing over time—helps resource managers assess the success of conservation measures and helps to identify populations at risk. Our scientists collect and present these data in annual stock assessment reports.
Scientists use small aircraft to observe and record harbor porpoise numbers and distribution. Under the MMPA, NOAA’s Southwest Fisheries Science Center conducts population estimates every 2 to 5 years to monitor the health, status, and trends of the population in its region. By comparing numbers collected over multiple years, scientists can spot trends, for instance, whether the population is increasing, decreasing, or remaining stable.
We have used DNA markers to study population structure among harbor porpoises living off the coasts of Alaska, California, Oregon, and Washington. NOAA scientists are studying this genetic evidence to determine whether different groups of harbor porpoises are functionally independent, or reproductively isolated, from one another.
Results of the study indicated that there is limited dispersal among groups. These results, along with data on harbor porpoise distribution and abundance, were used to redefine the management units used for assessing status. There are now six management units of harbor porpoise recognized off the coasts of California, Oregon, and Washington. In Alaska, genetic data are currently being generated to investigate the genetic relatedness of populations. Additional research is being conducted in various regions to help us better understand the population structure and movement patterns of harbor porpoises.
Harbor Porpoises in Alaska
Our research on the population structure, abundance, distribution, and diet of harbor porpoises provides information crucial for understanding this species in Alaska.
Recent Science Blogs
Biologists conducted survey flights of the shifting sand shoals of the Copper River Delta to search…
Annual summary reports of strandings of cetaceans (whales) and pinnipeds (seals and sea lions) that…
Incidental Takes and Interactions of Marine Mammals and Birds in Districts 6, 7 and 8 of the Southeast Alaska Salmon Drift Gillnet Fishery, 2012 and 2013
Marine Mammal Observer Program observations of the Southeast Alaska salmon drift gillnet fishery.
Outreach & Education
During March-June 2022, we will use passive acoustic moorings and visual observations to monitor…