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Pacific White Sided Dolphin

About AquaFacts: AquaFacts are a resource for students who are looking for information on the animals at the Aquarium or other Aquarium-related topics. Here, we’ve compiled some of the most frequently asked questions that we’ve received about Pacific white-sided dolphins. The answers come from our biologists and from reputable sources that we reference at the end of this page. If you have a question about Pacific white-sided dolphins that’s not addressed in this page or the references below, please feel free to email our librarian.

Pacific White Sided Dolphins

Questions & Answers

What does a Pacific white-sided dolphin look like?

Pacific white-sided dolphins are so named because of the white colouration on their sides and underneath. They are dark grey on top and have a pale gray streak along each side that starts narrow above the eyes and then widens towards the tail. They have small dark beaks and dark rings around their eyes. Adult females can weigh 85-145 kg, and reach lengths of 1.7-2.4 m. Males can weigh up to 198 kg, and reach lengths of up to 2.5 m.

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Where can you find Pacific white-sided dolphins?

Pacific white-sided dolphins are found throughout the temperate waters of the North Pacific Ocean from Japan to North America, and from the coasts of Alaska down to Baja, Mexico.

How many Pacific white-sided dolphins are there?

In the entire North Pacific, there are estimated to be approximately 900,000 Pacific white-sided dolphins. Dolphins travel in groups throughout their lives. In B.C., Pacific white-sided dolphins are usually encountered in groups of 10 - 100 animals, although some groups have been seen with 2,000 or more individuals.

How do Pacific white-sided dolphins reproduce?

Females have their first calf when they are seven to nine years old. Length of pregnancy (gestation period) is around 12 months. When the calves are first born they are approximately one metre long and weigh roughly 15 kg. Females will nurse their calves for eight to ten months and give birth approximately every 4.5 to five years. In B.C. most newborn calves are sighted between June and August but researchers have yet to determine whether there is a defined calving season here.

How long do Pacific white-sided dolphins live?

The maximum age recorded for a female Pacific white-sided dolphin is 46. The oldest male recorded is 42.

What do Pacific white-sided dolphins eat?

Pacific white-sided dolphins eat herring, capelin, Pacific sardines, squid, anchovies, salmon, rockfish, pollock, hake and other small fish.

What are the predators of the dolphins?

Bigg’s killer whales (transient) and sharks are both known to eat Pacific white-sided dolphins. When the dolphins first came back to B.C. waters, it took the killer whales a couple of years to figure out how to catch the fast-moving dolphins. Some killer whale pods drove groups of dolphins into small bays and killed them en- masse but this behaviour is no longer as common, suggesting the dolphins have learned to avoid this trap.

Have there always been Pacific white-sided dolphins in British Columbia?

Pacific white-sided dolphin remains are present in First Nations middens (waste heap) dating back 2,000 years, and were rare in B.C. during the 19th and 20th centuries. They were first spotted by fishermen in 1956 north of Vancouver Island, and sightings became more common in the 1980’s as Pacific white-sided dolphins started to spend more time in inshore waters and inlets along the B.C. coast. It’s possible that their long absence was related to a change in ocean temperatures and a shift in their prey distribution.

Are Pacific white-sided dolphins endangered?

In Canada, Pacific white-sided dolphins are listed as “Not at Risk”, due to their large population numbers and wide distribution, but in many parts of their range across the North Pacific Ocean, these dolphins are taken both directly and indirectly in fisheries. During the 1980s, up to 90,000 Pacific white-sided dolphins were killed in the Japanese, Korean and Taiwanese squid driftnet fisheries and the Taiwanese large-mesh driftnet fishery. Fortunately for the dolphins, these fisheries were discontinued following a 1992 United Nations resolution. In the late 1990s, there was a recorded decline in Pacific white-sided dolphins in the Broughton Archipelago, which correlated with the use of underwater acoustic deterrent devices by the salmon farming industries. These very loud sound sources were used to deter seals and sea lions from entering fish farms where they eat the farmed fish and cause significant damage to the farm infrastructure. Although acoustic deterrents have now been banned, ocean noise pollution is a problem that continues to threaten all cetaceans in B.C.

How can I help?

If you see a whale or dolphin off the coast of British Columbia, we would love to hear about it. Report your sighting at www.wildwhales.org.



References

  1. American Cetacean Society. Pacific White-Sided Dolphin Fact Sheet
  2. Carwardine, Mark. 2000. Whales, Dolphins and Porpoises. New York: Dorling Kindersley Publishing.
  3. Heise, Kathy. 1997. “Life history and population parameters of Pacific white-sided dolphins (Lagenorhynchus obliquidens).” Report of the International Whaling Commission. 47: 817-825.
  4. Mason, Adrienne. 1999. Whales, Dolphins and Porpoises. Canmore, Alberta: Altitude Publishing.
  5. Morton, Alexandra. 2000. “Occurrence, photo-identification and prey of Pacific white-sided dolphins (Lagenorhynchus obliquidens) in the Broughton Archipelago,” Canada 1984-1998. Marine Mammal Science 16(1): 80-93.

Permission is granted by the Vancouver Aquarium Marine Science Centre for classroom teachers to make copies for non-commercial use. This permission does not extend to copying for promotional purposes, creating new collective works, or resale.

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