Noaafishing Activities Continue to Restrict the Growth of at Least 1 Pacific Ocean Dolphin Each Year
Pacific White-Sided Dolphin
About the Species
Pacific white-sided dolphins, known for the distinct coloring that give them their name, are a playful and highly social marine mammal. They are also sometimes known as the "hookfin porpoise" because of their large, curved dorsal fin, though they are not technically porpoises.
In the United States, Pacific white-sided dolphins live off the coasts of California, Oregon, Washington, and Alaska. They can be seen traveling in schools of thousands, but group sizes are usually between 10 and 100 animals. These extremely playful dolphins are often seen "bow riding" (swimming near the front part of a ship) and jumping, somersaulting, or even spinning in the air.
Pacific white-sided dolphins in the United States are not endangered or threatened, but they are protected under the Marine Mammal Protection Act. A primary threat to Pacific white-sided dolphins is entanglement in fishing gear, such as gillnets and trawls.
NOAA Fisheries is dedicated to the conservation and protection of Pacific white-sided dolphins. We are working to help conserve this species through collaborative management, integrated science, partnerships, and outreach.
Population Status
NOAA Fisheries estimates the population size for Pacific white-sided dolphins in its stock assessment reports. In all, there are three stocks of Pacific white-sided dolphins in U.S. waters. Population trends for the North Pacific stock off the coast of Alaska are unknown. A survey of the two stocks off the coasts of Washington, Oregon, and California from 2008 to 2014 found a population of more than 21,000 dolphins.
Protected Status
MMPA Protected
- Throughout Its Range
CITES Appendix II
- Throughout Its Range
Appearance
These dolphins have a robust body, short rostrum (snout), and large dorsal fin compared to their overall body size. Their back, flukes (tail), and lips are black; their sides, dorsal fin, and flippers are gray; and their belly is white. They have a white or light gray stripe along their sides that extends from their eye to their tail, sometimes referred to as "suspenders." Pacific white-sided dolphins are most likely to be confused with common dolphins and Dall's porpoises because they have similar large light-colored flank patches.
The average adult Pacific white-sided dolphin weighs about 300 to 400 pounds and is between 5.5 and 8 feet long, with males being generally larger than females.
Behavior and Diet
Pacific white-sided dolphins feed on a variety of prey, such as squid and small schooling fish (capelin, sardines, and herring). They can dive underwater for more than 6 minutes to feed. They have small conical teeth that help them catch and hold on to their prey; each tooth row contains 23 to 36 pairs of teeth. Instead of using their teeth to chew their food, dolphins use their teeth to grip food before swallowing it whole—head first—so the spines of the fish do not catch in their throats. Pacific white-sided dolphins often work together as a group to herd schools of fish. Each adult eats about 20 pounds of food a day.
Where They Live
Pacific white-sided dolphins are pelagic, meaning they live in the open ocean and nearshore waters, but are unlikely to be found close to shore. They live in the temperate waters of the North Pacific Ocean. In the United States, they are found off the coast of California, Oregon, Washington, and Alaska. Worldwide, they are found in the southern Bering Sea (around the Aleutian Islands), Sea of Okhotsk, Sea of Japan, and Yellow and East China Seas to the south of Japan.
World map providing approximate representation of the Pacific white-sided dolphin's range.
Lifespan & Reproduction
The Pacific white-sided dolphin can live more than 40 years. Males reach sexual maturity around 10 years and females around 8 to 11. They mate and give birth from late spring to fall, except in the central Pacific, where calves are born in late winter to spring. Gestation is usually 9 to 12 months, and calves weigh about 30 pounds at birth and are about 3 to 4 feet. Mothers nurse their calves for up to 18 months and females usually give birth every 3 years.
Threats
Interactions with Fishing Gear
One of the main threats to the Pacific white-sided dolphin is entanglement in fishing gear. Dolphins can become entangled or captured in commercial fishing gear such as gillnets, seines, trawls, trap pots, and longlines.
Before a 1933 United Nations moratorium that banned large-scale drift nets, Pacific white-sided dolphins were often captured by Japanese fisheries. In addition, every year between 1978 and 1991, thousands of Pacific white-sided dolphins suffered mortality and serious injury when caught incidentally in high-seas fisheries for salmon and squid. These fisheries were closed in 1991 and no other large-scale fisheries have operated in the central North Pacific since 1991.
Ocean Noise
Low-frequency underwater noise pollution can interrupt the normal behavior of Pacific white-sided dolphins. Noise interference hinders their ability to use sound, which in turn disturbs their ability to communicate, choose mates, find food, avoid predators, and navigate.
Scientific Classification
| Kingdom | Animalia |
|---|---|
| Phylum | Chordata |
| Class | Mammalia |
| Order | Cetacea |
| Family | Delphinidae |
| Genus | Lagenorhynchus |
| Species | obliquidens |
Last updated by NOAA Fisheries on 09/16/2022
What We Do
Conservation & Management
All Pacific white-sided dolphins are protected under the MMPA. Our work supports the protection and conservation of Pacific white-sided dolphins by:
- Reducing interactions with commercial fishing gear
- Minimizing the effects of vessel disturbance, noise, and other types of human impacts
- Responding to dead, injured, or entangled dolphins
Learn more about our conservation efforts
Science
NOAA Fisheries conducts research on the biology, behavior, and ecology of Pacific white-sided dolphins to better inform management and policy. Examples include:
- Undertaking stock assessments to determine the status of populations and/or sub-populations
- Examining population structure, abundance, and dynamics using a variety of research techniques, including photo-identification and genetics
- Investigating causes of mortality (especially in unusual cases)
- Conducting ecosystem and habitat monitoring
Learn more about our research
How You Can Help
Don't Feed Wild Dolphins
Dolphins fed by humans lose their natural wariness and learn to associate people with food, causing them to beg for handouts and take bait and catch directly from fishing gear. This puts them at risk from vessel strikes and becoming entangled in or ingesting fishing gear. Dolphins may teach these behaviors to their young, thereby putting them at risk.
More on protecting wild dolphins and admiring them from a distance
Keep Your Distance
Report Marine Life in Distress
Report a sick, injured, entangled, stranded, or dead animal to make sure professional responders and scientists know about it and can take appropriate action. Numerous organizations around the country are trained and ready to respond. Never approach or try to save an injured or entangled animal yourself—it can be dangerous to both the animal and you.
Learn who you should contact when you encounter a stranded or injured marine animal
Report a Violation
Call the NOAA Fisheries Enforcement Hotline at(800) 853-1964 to report a federal marine resource violation. This hotline is available 24 hours a day, 7 days a week for anyone in the United States.
You may also contact your closest NOAA Office of Law Enforcement field office during regular business hours.
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Source: https://www.fisheries.noaa.gov/species/pacific-white-sided-dolphin
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