If there's one thing that gets my dander up, it's fishing next to a seal.
Harbour seals rebound on coast
Population has risen 10-fold since Ottawa began protecting the mammal, study says
By Larry Pynn, Vancouver SunMarch 3, 2009
The population of harbour seals has increased 10-fold to an estimated 105,000 on the B.C. coast since the federal government afforded the marine mammal protection from commercial harvest and bounties in 1970.
A new study by Fisheries and Oceans Canada found that the population has stabilized after decades of growth and appears to have returned to historic levels of more than a century ago.
The highest densities of harbour seals -- 13.1 seals per kilometre of shoreline -- occur inside the protected waters of the Strait of Georgia and compare with an average 2.6 seals per km outside.
The report by Peter Olesiuk, a federal marine biologist based in Nanaimo, notes the recovery of harbour seals has "renewed concerns over conflicts with fisheries and the impact of seals on fish stocks." But it also states that the "feeding habits of harbour seals and their role in the ecosystem are still poorly known" and that more research is required on their diet, foraging patterns, and energy requirements.
Studies in the Strait of Georgia indicate that while harbour seals are opportunistic predators, hake and herring account for about 75 per cent of their total diet.
Olesiuk said in an interview Monday that those two stocks are relatively healthy and may be able to support the seal population without problems. "There's a lot of places where we have large numbers of seals and they're not a conservation concern," he confirmed.
The greater issue involves a relatively few seals that target depressed fish stocks in estuaries and river mouths, he said. Seals have been culled on the Puntledge River on Vancouver Island to protect adult fish returning to their spawning grounds and juvenile fish going out to the ocean.
Olesiuk said it is also important to note that transient killer whales have benefited from increased numbers of harbour seals, their main prey source. Resident killer whales in comparison are fish-eaters.
The report states that harbour seals may be used as a general indicator of the status of marine ecosystems in the north Pacific, including a sentinel for chemical contaminants in high-level predators.
Harbour seals were over-hunted for their commercial pelts during 1879-1914 and 1962-1968, the report says. Bounty payments offered for predator control during 1914-1964 maintained populations below natural levels.
Harbour seals received protection under the federal Fisheries Act in 1970; aerial surveys at about that time estimated their numbers at 10,000 on the B.C. coast. The latest study found that the 105,000 harbour seals in B.C. in 2008 utilized almost 1,400 haul-out sites to rest, moult, and give birth.
Aboriginal people continue to hunt seals on a limited basis, not enough to affect their populations.
In a separate study, the Washington state department of fish and wildlife analysed the contents of 398 samples of harbour seals' feces from 17 sites in the San Juan Islands. It found evidence of 32 prey species, but found herring 57 per cent of the time, adult salmon 19 per cent, and walleye pollock 15 per cent.
The B.C. population represents almost one-third of the estimated 360,000 harbour seals in the northeast Pacific. Harbour seals are generally found on the coast within 20 km of land, but are known to range as far as 250 km up the Skeena River and 500 km up the Fraser River.
lpynn@vancouversun.com© Copyright (c) The Vancouver Sun
Author
Topic: Harbour seals rebound on coast (Read 4936 times)