Northern Southeast sea otter numbers up 4 percent
Will Ware goes subsistence fishing in Sumner Strait, south of Petersburg. But the administrator of the town’s tribal government says he finds fewer shellfish there these days.
“When you get onto the reefs you’re seeing that it’s just shell-laden all over the rocks and beaches. There’s gumboot shells everywhere, shrimp shells. It’s almost like a devastating sight to see on some of these islands and rocks,” he says.
The shells are leftovers from sea otters’ meals. A few decades ago, the federally protected marine mammals were hard to find. But that’s no longer the case.
The U.S. Fish and Wildlife Service and other agencies have been surveying Southeast
waters to determine the extent of otter growth.
Wildlife Biologist Verena Gill just released a new population estimate: 20,000.
“The reason it is increasing, both in distribution and in number, is because these sea otters are just recolonizing where they were extirpated from,” she says.
Otter fur is thick and warm, making it a valuable commodity. Russian, and later American, hunters killed so many that they disappeared from Southeast and most other coastal areas about a century ago.
Then, the state decided they should be brought back.
“In the late ‘60s, the Department of Fish and Game actually translocated otters from some remnant colonies that were left in Prince William Sound and the Aleutians and took them over to Southeast Alaska. And they’ve been increasing and expanding back into their original range since then,” she says.
Four hundred otters were brought to the outer coast of Southeast. Gill’s new population estimate means their numbers have risen 50-fold in the past 45 or so years.
But growth has not been even across the region. The south is seeing a 12 percent growth rate, while in the north, it’s only 4 percent.
“There isn’t the habitat otters really they like in northern Southeast that there is in southern Southeast. They tend to like water about 100 feet deep and there is a lot more shallow habitat available in southern Southeast Alaska with more of the kind of foods they like to forage on,” he says.
The reintroduced otters have expanded from the outer coast to inside waters. But it will take a while for large numbers to reach the mainland.
“But if they do move into the inner waters of Southeast I think it would be many, many years. There’s a lot of available habitat on the outer coast yet for them to recolonize,” she says.
But Gill says there’s no doubt the population will continue to increase and spread out.
A recent report from the Southeast Alaska Regional Dive Fisheries Association says otter expansion is reducing the region’s crab, sea urchin, sea cucumber and geoduck populations. That’s hurt commercial crabbers and divers who make their livelihood from the same species. (Read a story on that report.)
Gill says the worst impacts may come with the marine mammal’s arrival.
“Otters, when they move into a new area, they will go for the higher fat, high calorie, easy pickings. And then gradually their diet will revert to clams. Otters don’t eat themselves out of house and home, they just switch prey,” Gill says.
Diet studies show 90 percent of what sea otters eat is clams. The rest overlaps with what people harvest.
But Gill says the otters could boost the herring population. They eat sea urchins that consume kelp, where herring lay their eggs.
One factor expected to limit population growth is climate change. Gill says the warming ocean contains more neurotoxins and biotoxins. And it’s becoming more acidic, which will damage otter food.
“The shells of clams may become softer. It may impact invertebrate populations, so sea otters won’t have the forage they need. That will also impact people too,” she says.
Groups involved in the issue will get together prior to the next state Board of Fisheries meeting, January 15th in Petersburg.