2008 Peter Olesiuk on Seals
Peter Olesiuk a biologist from Fisheries and Oceans Canada, at the Pacific Biological station in Nanaimo, spoke at Camp Orkila about his department’s seal population research.
We have five seals in this area, two true seals (short foreflippers & limited land motility, ear holes) and three eared (can rotate hind flippers and walk around, ear flaps).
The Harbor Seal is found from California to Alaska. It’s non-migratory. In the 1970’s, their population was at an all-time low and both Canada and the US passed conservation laws. With protection, the Harbor Seal population has rebounded back to the numbers recorded around 1890. Olesiuk thinks the current population is at the natural level.
To study seals, they glue satellite trackers, depth meters, and stomach temperature meters to the seals’ fur. A typical Harbor Seal spends long sessions foraging in repeated dives. This takes 53% of its time. At low tide, it hauls out for 19% of the time, and the remaining 28% it is “milling,” or dozing around on the surface of the water. At low tide, about 61% of seals are hauled out, so when Fisheries does aerial flybys and photographs them, they can then extrapolate what the actual population must be.
Harbor Seals eat fish from fry size to 15 kilograms. Dedicated biologists collect their scat and analyze it. While regional seal diets vary, in general only about 3% of their diet consists of salmon. The rest is mostly forage fish, hake, and herring. They concentrate on hake from March to November and on herring from December to March. Since hake is a major salmon predator, large numbers of seals may actually help salmon. Indeed, when seal numbers rebounded from the ‘70’s, so did those salmon runs that were not overfished by humans.
How far do seals move from their haulout? In one study, they tracked seals out to 10 km from home. But in a more recent study, seals with trackers glued on to them really traveled, from the mouth of the Straits of Juan de Fuca up to the Queen Charlottes and back. This change could be because the seal population is now just about maxed out as far as available prey, and they have to look further afield.
The Northern Elephant Seal goes ashore in California twice a year, once to breed and once to molt. For the rest of the time, they are pelagic, going up the coast as far as Alaska. Recently, elephant seals have been molting at Race Rocks south of Victoria. This new site possibly reflects their recovery to over 100,000 seals after a low of only a few hundred. Now and then, an elephant seal is seen near our island.
The Sea Lion has greater mobility on land than the Harbor Seal. There are two species. The California Sea Lions are smaller, darker, with a steep forehead. They make the distinctive “ork, ork, ork” call. The Stellar Sea Lion is much larger and blonder, with a deep throated call.
The California Sea Lion was rare here before the 1960’s. Local numbers increased to about 300 in the 90’s, and are now even higher. As with the other seals, their numbers were lowest in the 1970’s, but are higher now.
There are no Stella Sea Lion rookeries in Washington, but there are some further north and south. The Western stock, from the Aleutians to the Kiril Islands north of Japan, have declined 85%, but our Eastern stock is doing okay.
Males arrive at the rookeries in May to compete for territory. Females come in June and almost immediately pup. After a week of staying with the newborn, the females mate with the male in the territory they’ve pupped in. Then they alternate days, one day foraging at sea, the next nursing their pup, and back to foraging. After about a month the pups can swim, and in August, they swim off with their mothers. Pups may suckle for up to three years.
To survey the population, scientists wait until the early pups are not yet a month old and the late mothers have already arrived, in July. As with the abovementioned seals, their population low was in the 1970’s at about 5,000. In 1910, the population was around 14K, in 2005 around 16K, and today around 14K.
Daily food requirements are estimated at:
Yearling Harbor Seal: 1.5kg, Yearling Stellar Sea Lion: 15kg
Female Harbor Seal: 2.4kg, Female Stellar Sea Lion: 20kg
Male Harbor Seal: 2.7kg, Male Stellar Sea Lion: 30kg
Stella Sea Lions are a dominant predator around here. Their scat reveals that they eat about equal parts rockfish, forage fish, and salmon.
The Northern Fur Seal breeds up along and on either side of the Aleutians. In winter, they migrate to about 10 to 200 km off the coast of California. By March they are off the Washington coast, and then in April they’re back north. Their population is declining, possibly due to competition from Sea Lions.
After Olesiuk’s talk, Glen R asked about the relation of Orcas to seals. Olesiuk said he was surprised to find that there is a close relationship. The graph showing the rise in Harbor Seal population matches the rise in the transient Orcas, the Orcas that eat seals, now at about 150.
We have five seals in this area, two true seals (short foreflippers & limited land motility, ear holes) and three eared (can rotate hind flippers and walk around, ear flaps).
The Harbor Seal is found from California to Alaska. It’s non-migratory. In the 1970’s, their population was at an all-time low and both Canada and the US passed conservation laws. With protection, the Harbor Seal population has rebounded back to the numbers recorded around 1890. Olesiuk thinks the current population is at the natural level.
To study seals, they glue satellite trackers, depth meters, and stomach temperature meters to the seals’ fur. A typical Harbor Seal spends long sessions foraging in repeated dives. This takes 53% of its time. At low tide, it hauls out for 19% of the time, and the remaining 28% it is “milling,” or dozing around on the surface of the water. At low tide, about 61% of seals are hauled out, so when Fisheries does aerial flybys and photographs them, they can then extrapolate what the actual population must be.
Harbor Seals eat fish from fry size to 15 kilograms. Dedicated biologists collect their scat and analyze it. While regional seal diets vary, in general only about 3% of their diet consists of salmon. The rest is mostly forage fish, hake, and herring. They concentrate on hake from March to November and on herring from December to March. Since hake is a major salmon predator, large numbers of seals may actually help salmon. Indeed, when seal numbers rebounded from the ‘70’s, so did those salmon runs that were not overfished by humans.
How far do seals move from their haulout? In one study, they tracked seals out to 10 km from home. But in a more recent study, seals with trackers glued on to them really traveled, from the mouth of the Straits of Juan de Fuca up to the Queen Charlottes and back. This change could be because the seal population is now just about maxed out as far as available prey, and they have to look further afield.
The Northern Elephant Seal goes ashore in California twice a year, once to breed and once to molt. For the rest of the time, they are pelagic, going up the coast as far as Alaska. Recently, elephant seals have been molting at Race Rocks south of Victoria. This new site possibly reflects their recovery to over 100,000 seals after a low of only a few hundred. Now and then, an elephant seal is seen near our island.
The Sea Lion has greater mobility on land than the Harbor Seal. There are two species. The California Sea Lions are smaller, darker, with a steep forehead. They make the distinctive “ork, ork, ork” call. The Stellar Sea Lion is much larger and blonder, with a deep throated call.
The California Sea Lion was rare here before the 1960’s. Local numbers increased to about 300 in the 90’s, and are now even higher. As with the other seals, their numbers were lowest in the 1970’s, but are higher now.
There are no Stella Sea Lion rookeries in Washington, but there are some further north and south. The Western stock, from the Aleutians to the Kiril Islands north of Japan, have declined 85%, but our Eastern stock is doing okay.
Males arrive at the rookeries in May to compete for territory. Females come in June and almost immediately pup. After a week of staying with the newborn, the females mate with the male in the territory they’ve pupped in. Then they alternate days, one day foraging at sea, the next nursing their pup, and back to foraging. After about a month the pups can swim, and in August, they swim off with their mothers. Pups may suckle for up to three years.
To survey the population, scientists wait until the early pups are not yet a month old and the late mothers have already arrived, in July. As with the abovementioned seals, their population low was in the 1970’s at about 5,000. In 1910, the population was around 14K, in 2005 around 16K, and today around 14K.
Daily food requirements are estimated at:
Yearling Harbor Seal: 1.5kg, Yearling Stellar Sea Lion: 15kg
Female Harbor Seal: 2.4kg, Female Stellar Sea Lion: 20kg
Male Harbor Seal: 2.7kg, Male Stellar Sea Lion: 30kg
Stella Sea Lions are a dominant predator around here. Their scat reveals that they eat about equal parts rockfish, forage fish, and salmon.
The Northern Fur Seal breeds up along and on either side of the Aleutians. In winter, they migrate to about 10 to 200 km off the coast of California. By March they are off the Washington coast, and then in April they’re back north. Their population is declining, possibly due to competition from Sea Lions.
After Olesiuk’s talk, Glen R asked about the relation of Orcas to seals. Olesiuk said he was surprised to find that there is a close relationship. The graph showing the rise in Harbor Seal population matches the rise in the transient Orcas, the Orcas that eat seals, now at about 150.