Conservationists along British Columbia’s coast may have felt like they were facing a Sophie’s choice in recent years: what if there are two endangered species in the same habitat, but one of them eats the other? That’s the conundrum presented by sea otters and abalone.
Otters are returning to their historical range after being hunted nearly to extinction during the fur trade, while the succulent abalone snail, which has great importance to coastal First Nations, is endangered after it was fished nearly to extinction in the late 20th century. Today, abalone fisheries are closed as the species slowly recovers, while sea otters are returning to their former habitat and noshing on the abalone buffet. Do conservationists have to choose between them? According to new research from former Hakai scholar Lynn Lee, the answer is no.
Lee, a PhD candidate at Simon Fraser University, studied more than 60 sites from Vancouver Island to Haida Gwaii. At the latter, otters had yet to arrive, while along Vancouver Island, they had returned in force. How, Lee wondered, were the already vulnerable abalone responding? The answer was a treasure trove of ecological data that showed Lee abalone would probably be just fine: they’re just returning to an old equilibrium. “It’s a shifting baseline, not a decline,” says Lynn. “[The otter recovery] is not going to endanger the prey ecologically. They’re still going to persist and survive with that predator as they have for thousands of years.”
Gathering this data was something of a logistical adventure, involving cooperation with government, First Nations, volunteers, and fellow academics. Over two summers, Lee went right to the source, below the coastal waters at each of her sites. Divers counted abalone up to 10 meters beneath the chilly waves, also noting kelp cover and otter presence. Two years of number crunching later, she had her data, and the initial results confirmed there were indeed fewer abalone where otters were present—up to 16 times fewer. But she also found it wasn’t as simple as otters eating them outright.
In otter sites, there were more abalone deeper down, which in turn changes how they spawn and how their larvae disperse in the water. More abalone had also hidden in crevices. (Lee hypothesizes that abalone, which she jokingly calls “the fastest snail in the west” for its ability to move away from predators, learned to seek shelter when otters show up.) Otters also brought other indirect changes, including eating urchins and thereby increasing kelp, which offered both more snail food and more places to hide. It’s complicated, but Lee says that it’s simply adjusting to conditions that are more in line with historical norms.
Lee, who is now a marine ecologist for the Gwaii Haanas National Park Reserve, says abalone fisheries are completely closed along the coast at present, but she hopes that the ecosystem continues to recover and both species will be just fine.