August 19, 2021 — The maritime fur trade, beginning in the 1700s and centered on the North Pacific Ocean, killed around one million sea otters and left the species fluttering on the verge of extinction with a global population as low as 1,000. On the west coast of Canada, the animal didn’t make it. The last sea otter was seen in the region in 1929, off Vancouver Island, British Columbia. But beginning in the 1960s, restoration efforts have turned back the clock on British Columbia’s sea otters. From an initial 89 sea otters relocated from Alaska, a population of 8,000 is now expanding in the province. Yet after generations of their absence, the surge in sea otters is stoking the resentment of some residents.
The trouble is, a sea otter consumes 25 to 30 percent of its own body weight every day. The otters’ voracious appetite can have dramatic ecological effects. It doesn’t help, either, that sea otters eat many of the same seafoods that humans in the area have long favored, such as crabs and clams, sparking conflict with shellfish fisheries and leading some to argue that the reintroduction effort has worked too well.
Now, a new study suggests that conservation efforts may have indeed overshot the mark—and the reason why is particularly interesting.
When thinking about restoring natural ecosystems, the goal for many would likely be to see a species rebound to its carrying capacity—that is, the maximum population a given habitat can support, free from human impact. So, for the sea otter, that would be to roll back the effects of colonization, the commercial fur trade, hunting, land development, and other pressures to a time when abundant sea otters may have dwelled on the coast, gorging on abalone and other shellfish. But taking that as your goal is to overlook the way Indigenous peoples extensively managed the sea otter population for thousands of years.
Led by Erin Slade, a graduate student at British Columbia’s Simon Fraser University, new research examining the sizes of mussels found along the coast challenges the assumption that late-Holocene sea otter populations would have ever been at, or even near, their carrying capacity.