Pacific white-sided dolphins
A super pod of dolphins
The oldest recorded age
The average weight of a newborn
Number of Pacific white-sided dolphins in North Pacific
Length of pregnancy
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.
Pacific white-sided dolphins eat herring, capelin, Pacific sardines, squid, anchovies, salmon, rockfish, pollock, hake and other small fish.
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.
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.
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.
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.
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.
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.
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.
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