Endangered Species Information Network

Harbor Porpoise

Name: Harbor Porpoise (Phocoena phocoena)

CLASS: Mammalia
ORDER: Cetacea
SUBORDER: Odontoceti
FAMILY: Phocoenidae

Status: Species of Concern in Washington State and Canada. No Federal listing.

Harbor porpoise occur in the Northern hemisphere in coastal areas and inland waters and occasionally are seen in estuaries and even travel up coastal rivers. While some stocks of harbor porpoise migrate, the one in the Puget Sound seems to be localized to a specific range. Generally harbor porpoise are seen in waters less than 200 m deep.

Harbor porpoise are subject to numerous pressures. Natives take substantial numbers off Greenland for food and oil. They become entangled in salmon and cod nets in the eastern North Atlantic; in the Pacific they are caught in trawl and gill nets; their numbers were severely depleted in the Black and Baltic Seas by drive fisheries and netting. Pesticides, destruction of habitat by coastal development, and boat traffic may all be responsible for the decline of most populations of harbor porpoises. Most of the research on harbor porpoise has been conducted in UK , Sweden and Denmark to mitigate losses due to fisheries.

Harbor porpoise were once the most abundant cetacean species in the south Puget Sound . Today they are rarely seen south of Seattle. They are listed as a Species of Concern in Washington State and in Canada , but the US Federal government has not listed the Washington stocks. The discussion that follows will focus on the stocks found in the Washington Inland Waters and Coastal areas.

Description: The harbor porpoise is one of the smallest of the cetacean species. They are rarely longer than 1.7 m and weigh less than 80 kg. The females are larger than the males. Their backs are dark gray to dark brown shading to lighter gray on the sides and white on the belly. Their flippers and fin are dark. Their dark coloration distinguishes them from the only other porpoise in the region, the Dall, which has showy black and white markings, similar to the Orca. Their behavior is also different from the Dall. They surface in slow rolls and avoid humans and boat traffic, while the Dall will seek out fast boats to bow ride.

The body is stocky with a blunt rostrum (beak). The dorsal fin is triangular, sloping backward and located to the back of the center of the body. Usually all one will see of the harbor porpoise is the arc of its back and the small triangular dorsal fin. The photo above showing the porpoise with its head out of the water is most unusual.

Harbor porpoises are normally seen singly, or in small groups of 6 to 10 animals. In recent years there have been rare sightings of 50 to 100 in the springtime at locations north of the San Juan Islands.

Females reach maturity at about 4 years. Gestation is 11 months and births occur in spring to mid summer. The harbor porpoise’s lifespan is usually less than 20 years.

They feed on squid, herring, small schooling fish and sardines. It is thought to consume 10% of its body weight each day. It carries one of the largest contaminant loads found in cetaceans including PCBs and other metals and chemicals. Since it appears to reside in localized regions, the “signature” of contaminants can be related to the part of the coastal waters it inhabits.

The harbor porpoise does not vocalize in the audible range of sound as does the Orca. Instead, it produces high frequency sounds that are often clicks or bursts in the frequency range of 110 kHz to 170 kHz. These sounds are thought to be used for echolocation and communication.

Threats to the harbor porpoise include: loss of habitat, crowding by humans and human activities, loss of food sources, noise, and a weakened physical condition from the heavy burden of contamination in their bodies. In addition, many are caught in gillnets, drowned as fisheries by catch, stranded and eaten by transient orca.

For Washington State the harbor porpoise is found in the Washington Inland Waters (WIW which is mostly the Puget Sound) and along the coast. NOAA Fisheries considers the stock in the WIW to be different from the Northern Oregon/Washington Coast Stock for their Stock Assessment Reports (SARs). The most recent SAR for the harbor porpoise in the WIW was done in 2006 and at that time the population was estimated to be 10,682 and the trend was listed as unknown. The most recent SAR for the Northern Oregon/Washington Coast Stock was done in 2009 and the population was listed as 37,745.

The harbor porpoise is protected under the Marine Mammal Protection Act of 1972 as amended. Section 117 of the Marine Mammal Protection Act (MMPA) requires 3 regional Scientific Review Groups under NOAA to advise and report on the status of marine mammal stocks within the Pacific coastal region. The SARs are the mechanism for identifying actions to protect a species.

NOAA Conservation Efforts: The National Marine Fisheries Service promotes sustainable fisheries, recovery of protected species, and the health of coastal marine habitats in the USA. In 1996, NMFS convened two take reduction teams (TRT) to mitigate by catch of harbor porpoises in gillnet fisheries. These were the Gulf of Maine Harbor Porpoise TRT and the Mid-Atlantic TRT. The Gulf of Maine TRT addresses gillnet fisheries in waters from Maine through Rhode Island and the Mid-Atlantic TRT addresses waters from the Connecticut/New York border through the North Carolina/South Carolina border. The teams submitted draft take reduction plans to NMFS and the agency finalized the plans in 1998.

The Harbor Porpoise Take Reduction Plan requires commercial fishermen to use pingers in gillnets in designated times and areas. There are also times and areas where gillnet fishing activities are prohibited. The HPTRT continues to meet to monitor the progress of the take reduction plans in achieving the MMPA long-term goal of reducing harbor porpoise by catch to a zero mortality and serious injury rate.

More Information:

Pacific Biodiversity Institute Page on Marine Mammals
Marine Mammal Protection Act
NMFS Southwest Fisheries Science Center Harbor Porpoise Information
NMFS Alaska Fisheries Science Center Harbor Porpoise Information
NMFS Take Reduction Planning
NMFS Harbor Porpoise Take Reduction Plan

References:

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