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 porpoise 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. Females are slightly larger than males.
Harbor porpoises have a medium-sized triangular dorsal fin. Their back is dark gray while their belly and throat are white. They have a dark gray chin patch and also intermediate shades of gray along their sides.
Behavior and Diet
Harbor porpoise 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. 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 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 Monterey Bay, CA 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.
Entanglement in Fishing Gear
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 (in Canada).
Underwater noise pollution interrupts the normal behavior of harbor porpoises and interferes with their communication.
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 2016, we issued 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. When stranded animals are found alive, NOAA Fisheries and our partners assess the animal’s health and try to return it to the water. 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 identify strandings due 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 can have implications for human health and welfare.
Harbor porpoises are protected under the Marine Mammal Protection Act of 1972, as amended.
Regulatory Actions & Documents
- FInal Amended Take Reduction Plan (75 FR 7383)
- Delay in implementation of new seasonal pinger requirements for the New England component (75 FR 12698)
- Proposed Amended Take Reduction Plan (74 FR 36058)
- 1998 Take Reduction Plan Regulations (63 FR 66464)
- Status Review and Listing Determination (66 FR 53195)
- Draft Status Review (66 FR 40176)
- 1999 Status Review (64 FR 465)
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. 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 DNA evidence to determine whether different groups of harbor porpoises are functionally independent of one another 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 their 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, DNA markers are currently being assessed 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 porpoise.
Research & Data
NOAA Fisheries Protected Resources Division biologists conducted six survey flights of the shifting sand...
NOAA Fisheries Protected Resources Division (PRD) conducted six survey flights of the shifting sand shoals...
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
Southeast Alaska salmon drift gillnet fishery observer manual