As Canada kicks off its controversial seal hunting season this week, several species of seals around the world face uncertain futures.

In Finland, the Saimaa ringed seal (Pusa hispida saimensis), one of the world's few freshwater seals, is likely to become extinct in a few years, according to the Finnish natural resources agency, Metsähallitus. Its population has dropped to just 260 due to "warmer winters, drownings of seals caught in fishnets and traps, and the dispersed nature of the seals themselves," The Helsingin Sanomat newspaper reports.

Saimaa ringed seals form dens in snow and ice. In warmer winters, those dens melt, exposing young seals to the elements before they have had a chance to acquire their protective layers of fat. Lack of snow and ice also leave them exposed to fishermen, who sometimes kill them to prevent them from competing for their catch.

Disappearing ice is also becoming a problem for Baltic ringed seals (Phoca hispida botnica). "Climate models predict that the ice on the Baltic Sea will decrease by 50 to 80 percent by the end of the century," Antti Halkka, chair of WWF Finland's seal unit, told the Finnish news service YLE Uutiset. Like the Saimaa ringed seal, Baltic ringed seal pups live in ice dens where they are protected from predators and icy waters and fed by their protective mothers. Last year, according to WWF Finland, more than half of Baltic seal pups born in three of their four habitats died because ice levels were too low.

Another freshwater seal, Canada's Lac des loups marins harbour seals (Phoca vitulina mellonae), could soon become listed as an endangered species in Canada, according to a report in The Nunatsiaq News. There are just 100 to 600 of these rare seals left (although most scientists believe the number is closer to the lower end of that range), and according to documents at the government's Species At Risk Public Registry website, planned hydroelectric plants on the seals' home lakes would result in the "disappearance of under-ice shelters and ice-free zones, changes in the availability of prey and mercury contamination."

One seal species that doesn't rely upon ice is the Hawaiian monk seal (Monachus schauinslandi). But that doesn't mean it is less endangered. Research by Jennifer Schultz, a doctoral candidate at the Department of Zoology and Hawaii Institute of Marine Biology at University of Hawaii, Kaneohe, shows that Hawaiian monk seals face a genetic bottleneck, with the lowest genetic diversity of any mammal species ever studied. According her paper, published in the January-February 2009 issue of Journal of Heredity, this increases the risk that the species could be wiped out by disease. As to what caused this lack of genetic diversity, Schultz's DNA tests revealed that all existing monk seals are probably descended from as few as 23 individual seals after the species was hunted to near-extinction in the Nineteenth Century.

Meanwhile, despite protests by many conservation and animal-rights organizations, Canada's seal hunt continues, with an increased government-set quota of 338,000 baby harp seals (Phoca groenlandica). According to The Canadian Press, about 9,500 seals were killed on Monday, the first day of the season. Harp seals aren't endangered -- in fact, an estimated 6.5 million of them live in Canada -- but many believe this hunt will not put the species on good footing for the future.

"The last time Canada allowed this many seals to be killed, the harp seal population was reduced by as much as two thirds within a decade," Rebecca Aldworth, director of the Canadian branch of Humane Society International, said in a statement.

Those fighting the seal hunts -- who say the hunting techniques are inhumane and that there is no real economic market for the seal furs -- did gain some support in recent weeks: Russia has decided to ban the hunting of baby seals, and the European Union is considering a ban on trade in products made from seals.

Image: Hawaiian monk seal (Monachus schauinslandi), Wikipedia