What is a Harbour Seal?
Harbour seals belong to a group of mammals called Pinnipeds (“feather foot”), which includes seals and sea lions. Harbour seals are found throughout the world’s oceans, and five subspecies are currently recognized. The local species is the eastern Pacific harbour seal, Phoca vitulina richardsi. Like most other marine mammals, they have a thick layer of fat which keeps them insulated from the cold water. Seals differ from sea lions in that they have no external ear flaps, they have short, fur-covered front flippers, and they can’t raise their head and shoulders well while on land. Seals propel themselves through the water by sculling with their hind flippers and steering with their front ones. They move quite awkwardly on land by undulating their body, “inch-worm” style. Sea lions, on the other hand, have external ear flaps, longer furless front flippers, and rear flippers that can be rotated forward. They move on land by “walking” with both pairs of flippers, and can raise their head and shoulders by supporting their weight on their front flippers.
Harbour seals of both sexes are usually 1.2-1.6 m in length and weigh 60-80 kg. The colour of their fur varies from black or brown to tan or grey, with light or dark spots. They can often be seen “hauled out,” resting on rocky reefs, sand bars and boulders, and are common throughout Victoria area harbours. Though harbour seals were once killed as pests for their perceived competition with fisheries, public sympathy has swung in their favour and their populations have rebounded. They are an important part of coastal ecosystems.
How do harbour seals live and reproduce?
Harbour seals are agile swimmers. They use side-to-side strokes of their rear flippers for propulsion, while their front flippers are used for steering. Harbour seals eat fish (e.g. sculpins, small flatfishes and rockfishes, greenlings, smelts, perches, hake, herring and salmon), crustaceans (e.g. crayfish, crab and shrimp), and molluscs (e.g. octopus and squid). In the Salish Sea, one of their most common foods is hake, a deep-sea fish. When foraging, harbour seals usually make short (3-7 minute) dives to less than 100m; however, they can dive to over 400m and remain submerged for up to 40 minutes.
Courtship and mating take place underwater, but the young are born on land. In southern B.C., the birthing season is from July to August. Pups weigh about 10 kg at birth, and can crawl and swim within a few hours. Harbour seals do not congregate in large rookeries to mate, as do other pinnipeds. Rather, they breed in small, scattered groups throughout their range. Males may live for 20-25 years, and females for 30-35 years.
Where do harbour seals live?
Harbour seals are the most widely distributed of the pinnipeds. They live along coastlines in temperate and arctic waters of the north Pacific and north Atlantic. On the west coast of North America, they are found as far north as the Aleutian Islands in Alaska, and as far south as Baja California. Harbour seals usually stay within 25 km of shore, and remain in one general location throughout their lives. They sometimes venture into fresh water such as rivers and lakes to feed, and some populations even reside exclusively in large freshwater lakes.
Harbour seals are common inhabitants of virtually all of the harbours in the Victoria area.
Why are harbour seals important?
As a higher order predator, the harbour seal is an important indicator species. In other words, the health of seal populations can tell us a lot about the health of our marine ecosystems. Predators help to control the populations of their prey, which is important for the overall function of the food web.
How have people used harbour seals?
Harbour seals were hunted by First Nations of B.C. for their pelts, meat and oil. A small number of animals are still taken in subsistence hunting. Between 1900 and the early 1960s, harbour seals were hunted commercially and to reduce competition with humans for commercial fish stocks. The Department of Fisheries and Oceans offered a bounty on seals between 1913 and 1964, causing populations to decline substantially. The Fisheries Act now prevents killing of harbour seals except with a permit. As a result, populations of harbour seals have returned to close to historic levels. In Georgia Strait, the population was estimated at 39,000 harbour seals in 2008.
Not everyone is happy with the recovery of harbour seal populations. Seals are known to prey on farmed salmon, and interfere with the gear of commercial fishers. Some commercial fishers are concerned about competition for commercially valuable fish stocks and they would like seals to be culled again. Other people feel that harbour seal populations should be left to reach a natural balance. Such differing views present a major challenge for policy makers and regulators.
What threatens harbour seals?
High levels of toxic organochlorine chemicals (e.g. DDT, dioxins, furans, PCBs) have been found in harbour seals. Although these chemicals are now prohibited from being discharged into the environment, they take a very long time to break down. Therefore, they continue to be absorbed directly by small organisms, and ingested through food by higher predators such as harbour seals. Other chemicals such as hydrocarbons (oils, gasoline, solvents) and heavy metals may also threaten the health of seals. Harbour seals can become entangled in debris such as discarded fishing nets, ropes and plastic wrapping bands.
Disturbance by humans, particularly during the pupping season, can be detrimental to harbour seals. When boats pass close to seal haul-outs, the animals usually flee into the water. If this occurs often, it can cause stress to pups and nursing mothers, prevent them from conserving enough energy and fat reserves, and eventually lead to sickness or death.
How can I help protect harbour seals?
For information on how you can help protect harbour seals, please refer to our How Can I Help?
Additional Links & Information © top image courtesy of Minette Layne, bottom image courtesy of Jody Watson