by Todd McLeish
By the end of the morning, we tallied 418 adult sea otters and 304 pups, which was less than half the usual number Dunlop records in the area. We were unable to survey the entire basin, though, and the animals were more widely scattered than Dunlop usually sees, so it is unlikely we saw them all, especially given the conditions.
We departed Nuchatlitz in midafternoon and picked up a good breeze to carry us east along the calm Esperanza Channel, then turned south on Hecate Channel, where the wind died and we slowed and glided by three salmon farms and little else. The channels separating Nootka from Vancouver Island are less than a mile wide but up to nine hundred feet deep in places, thanks to the area’s geological history as a fjord carved by glaciers. The waters well offshore were far shallower than the protected channels. Sea otters were scarce in the channels, however. Dunlop said that five years earlier a raft of about fifty otters moved slowly through the channels, exploiting the little available food before returning to the outer coast. It took us four hours to cruise the last three miles to the town of Tahsis, where we stayed the night and I caught the floatplane for home, while Dunlop planned to continue sailing for several more weeks.
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BEFORE THE FUR TRADE, many of the approximately twenty thousand First Nations people who lived in tribal villages around Nootka Sound were expert sea otter hunters, but the pelts became the sole possession of the highest-ranking chiefs, who wore otter-skin robes and anklets to signify their rank. Dunlop called such attire “the crown jewels” of the tribe. The fur trade led to a collapse of that societal practice because individual hunters often sneaked off to trade or sell otter skins without having to give them to the chief.
According to Dunlop, the fur trade also triggered a significant change in the diet of the local tribes. In an archaeological excavation of a traditional refuse heap, or midden, at Friendly Cove, scientists revealed a distinct layer in the midden that corresponds to the time when sea otters disappeared from the area. “Prior to 1792 and for about four or five thousand years before that, the midden is dominated by hard-shelled animals like barnacles, snails, and all kinds of small mollusks,” Dunlop said. “But after 1792, clams became dominant.” He believes this is a clear indication of the influence of sea otters on the diet of these First Nations peoples.
Prior to the fur trade and their disappearance, the sea otters would have suppressed the population of clams, urchins, and other large invertebrates through their own foraging. That left the less appealing hard-shelled mollusks for the Natives to collect and eat. But when sea otters became extirpated, the apex predator no longer kept populations of the larger invertebrates in check, allowing them to expand dramatically and leading to a change in the diet of the tribes. Now that sea otters have returned to the area and are competing with the First Nations people for those same large invertebrates, Dunlop thinks the tribes should consider returning to some of their historic foods.
“It’s been more than two hundred years, so the people have probably forgotten what foods were very prevalent back in the day when there were sea otters here,” he said. “The midden at Friendly Cove before 1792 will give you a picture of what people were eating at that time.” He calls them “otter-proof foods” because they were species that sea otters could not easily break open, like red turban snails and moon snails. “There are many, many more species of mollusks, large gastropods, or snails that are out there that I think people have forgotten were once part of their diet. If you think about it that way, it’s easier to accept the change that comes in the ecology out here from having sea otters and kelp.” But Dunlop hasn’t had much success convincing the tribes to rethink their diets. He said he “got some pretty shocking dismissals” when he suggested it in Alaska, though he believes that some recognize that the idea makes sense.
Perhaps the First Nations people’s resistance to the idea spawns from the fact that the tribes were not consulted when sea otters were reintroduced to the region in the 1970s. A decision was made, a site was selected, and the animals were dropped off without any communication with those who would be affected. I would have been pretty unhappy about that, too. Although there was little initial backlash by the tribes back then, there is considerable resentment today when they see protected otters eating food they think should be their own. “Some people have hundreds of sea otters in their front yard and they’re not allowed to disturb them,” Dunlop said.
A management plan Dunlop is preparing for the tribal council is not going to address the issue of competition. Instead, it aims to allow the tribes to establish a sea otter hunt with the goal of reinstating their custom of wearing their ceremonial regalia. Dunlop said the plan will likely recommend a “ceremonial harvest” of about sixty to seventy animals per year from across the British Columbia population so no subgroup is adversely affected.
Although the plan is far from complete and isn’t a priority for the tribal council, just talking about it is raising red flags among wildlife enthusiasts. Whenever the subject comes up, Dunlop envisions headlines reading “otter slaughter” that do not accurately reflect what will likely be proposed. Which may be one reason why the tribes are still discussing the idea and an otter hunt is not on the horizon. “The people who oppose any kind of sea otter management are those that don’t live in close proximity to the animals and don’t have their way of life disrupted,” Dunlop said. “I think the people here have been extremely tolerant of these animals. The burden of that tolerance falls on the people here who can’t get their customary foods very easily anymore.”
Chapter 13: Gaining Ground
MOSS LANDING, CALIFORNIA
ALTHOUGH SEA OTTERS are best known for living in rocky, kelp-dominated habitat, where they play a key role in the maintenance of the ecosystem, that is not the only habitat where they’re found. About 25 percent of the habitat in the central part of their California range is soft, sandy sediment with little or no kelp. The long, smooth coastlines of Pismo Beach and Estero Bay, as well as nearly the entire stretch of coast from Monterey to Santa Cruz, are sandy embayments, and sea otters are found there, too. That’s typically where the nonterritorial males hang out in large groups, feeding on fat innkeeper worms and burrowing clams and what Tim Tinker calls “episodically abundant prey” like Dungeness crabs, sand dollars, and squid. These prey items are episodically abundant because they are available to the otters only during short windows of time when the creatures move closer to shore during their breeding season. There may be resting groups of eighty to one hundred male sea otters gathered together in sandy habitat, but seldom will a mother and pup be among them. A few juvenile and subadult females may be mixed in with the males, but those have not yet begun to breed. Once they do, the females usually limit themselves to the food-rich areas of the kelp forest.
Sea otter density is quite low in soft-sediment habitats, with an average of just two otters per square kilometer compared to five or six in rocky habitat—and twice that in the uniquely productive area of the Monterey peninsula. Otter density is also more variable in sandy habitat because it tends to be an otter travel zone, as mobile males come and go from season to season, tracking the episodically available prey from place to place. On a cold fall morning whale-watching excursion north from Monterey, I traveled more than a dozen miles along the sandy habitat of coastal Monterey Bay before seeing my first sea otters. When the first whales came into view just off the town of Moss Landing, several dozen sea otters were resting and feeding there, too. They were perched at the edge of the nutrient-rich Monterey Canyon, an underwater canyon that extends ninety-three miles offshore and reaches depths of nearly twelve thousand feet. At the mouth of the canyon is Elkhorn Slough, a narrow tidal estuary that divides the town of Moss Landing. It’s the only estuary within the range of the southern sea otter. And it’s there that the otters are just beginning to reveal another element of their remarkable ecological influence.
Located about halfway between Monterey and Santa Cruz, Moss Landing
is a quiet village on Highway 1 in the Salinas Valley, an important area for the commercial production of fruits and vegetables. When I visited, the large farm stands in town were selling artichokes and grapefruits at ten for a dollar, and avocados at seven for a dollar, prices far below what I’ve ever seen anywhere in the East in my lifetime. The most prominent feature of the community, besides the natural gas–fired power plant and its two massive concrete smokestacks, is Elkhorn Slough. At its inlet to the bay, a marina and yacht club share space with small businesses renting kayaks to tourists, while most of the inland properties surrounding the slough are protected by private conservation groups and the Elkhorn Slough National Estuarine Research Reserve. Although the community may be best known beyond the immediate region as the home of the Monterey Bay Aquarium Research Institute and the Moss Landing Marine Laboratories, the slough dominates its geography and culture.
Unfortunately, Elkhorn Slough is the destination for large quantities of polluted runoff from the adjacent farmlands and roadways, negatively affecting the health of the waterway. Nutrients in the runoff fuel massive algae blooms that suck the oxygen from the water and impair water quality, making it, according to Tinker, the most unhealthy estuary in the state. Yet because the slough is tidal, enabling clean ocean water from Monterey Canyon to flush the pollutants from the slough, it continues to host an enormous abundance of wildlife, including more than a dozen species of shorebirds, hundreds of California sea lions and harbor seals, and a growing complement of sea otters.
Until early 2014, rafts of seventy to ninety sea otters—mostly males, but also a few subadult females—were regularly observed from the marina and kayak launch just inside the seawall protecting the entrance to the slough. Several months later, however, most had moved a mile or so deeper into the slough, probably because of recent episodes of shark predation. On my visit, just two subadult males were observed at the entrance, wrestling with each other like ten-year-old boys, pushing and slapping and grabbing and grunting as they rolled over and over together in what appeared to be gleeful play.
I was there with Tinker and three young otter biologists as they conducted an informal assessment of Elkhorn Slough’s otter population and attempted to identify previously tagged otters. Traveling aboard the US Geological Survey vessel Pursuit, we passed a dock covered with nearly fifty noisy sea lions, cruised beneath the bridge carrying Highway 1, and proceeded down the main channel into the slough. It was high tide, so the abundant eelgrass on either side of the channel was barely visible, but harbor seals were lounging on the banks, willets and elegant terns called out loudly as they flew parallel to our route, and monarch butterflies, which winter in enormous aggregations in trees just a few miles up the coast, slowly floated overhead.
Tinker says that sea otters use the variable habitat in the slough in different ways. Large mollusks are abundant in the main channel and can be an important source of protein for the otters, but they require considerable digging to unearth, so they are often not the preferred prey. The eelgrass beds that grow in dense canopies along the banks of the first mile or two of the slough—which previously had only survived in tiny patches before the sea otters moved into the area—provide nursery habitat for fish and a place for crabs and invertebrates to hide, so otters can often find a meal there. When sea otters first became resident in the slough around 2001, they confined themselves to the first half mile of the waterway, where they consumed most of the fist-size rock crabs and the smaller invasive green crabs. But as otter numbers grew, they expanded deeper and deeper into the slough to take advantage of different prey and habitats.
As we approached Seal Bend, where a large raft of male otters regularly congregated in late 2014, biologist Sarah Espinosa set up a tall antenna, turned on a radio receiver, and dialed in the frequencies of the seventeen resident otters (out of approximately eighty total residing there) that have been implanted with transmitters. Every day, a team of volunteers visits the slough to locate each of the otters and assess its behavior and activities. The first tagged otter we detected was identified as Otter 3421, a subadult female who we found a few hundred yards from the raft of males. A steady beeping noise from the receiver indicated she was resting at the surface, but then the sound stopped, probably because she had dived beneath the surface, where the transmitter cannot be detected. When she popped to the surface again, we heard one loud beep before the quiet steady pulse resumed.
Glancing ashore at Seal Bend, we saw two volunteer otter spotters using high-powered telescopes and an antenna-and-receiver setup like the one we were using on the boat. They counted forty-four otters in the raft, all drifting with the current and then swimming upstream en masse to rest and drift some more before repeating the process. The otters were trying to remain in their preferred section of Seal Bend, a two-hundred-yard-wide strip of eelgrass, but with the strong current and no kelp to hold onto, they found it necessary to repeatedly swim upstream to maintain their place. With every tagged otter the spotters found, they noted its location, behaviors, and a wide variety of other information. Determining the otter’s exact position in the slough is especially important, because when combined with other data, it indicates the specific habitat it is using, which helps the scientists establish the demands placed on different sites. In addition to the data collected every day of the year by the volunteers, biologists like Espinosa regularly spend up to twelve hours at a time watching one individual otter to establish its activity budget—everything it does throughout the day, from the location and length of its foraging dives to the prey it consumes and the tools it uses to open its prey. “It’s very unique to have an animal in the marine environment that will go down and bring its food to the surface to show us. That’s how we have this amazing data set of foraging that doesn’t exist for any other marine species,” said Brent Hughes, a University of California, Santa Cruz, doctoral student.
Hughes is the one who made the surprising discovery about the role that sea otters play in the maintenance of the health of this estuary ecosystem. Biologists hadn’t paid much attention when the sea otters moved into Elkhorn Slough in the 1980s, or when the animals disappeared for a short time in the late 1990s. The otters were mostly males, and they initially were not year-round residents, but when they returned in the early 2000s, they were joined by some females and established a permanent subpopulation. But Hughes wasn’t interested in the otters. He was studying the eelgrass, the long ribbonlike green stems of seagrass that grow in extensive beds in sandy substrate; like kelp, eelgrass is home to an abundance of invertebrates and serves as nursery grounds for many species of fish and other marine creatures.
As in every other estuary on the West Coast, the Elkhorn Slough eelgrass beds had been in a steady state of decline for many years. Hughes could see it from early aerial photographs and from measurements other scientists had taken for several decades. As fertilizers and other runoff from nearby farmlands found their way into the slough, those nutrients caused an increase in algae, which attached to the eelgrass blades, denying them access to sunlight and choking the life out of them. It’s a process called eutrophication, a natural phenomenon in some lakes but a result of pollution in estuaries. When Hughes went to Elkhorn Slough to make measurements of the eelgrass beds, expecting to find continuing eutrophication, he instead saw healthy new growth and lots of tiny microorganisms grazing the algae off the eelgrass blades. “The seagrass was really green and thriving where there were lots of sea otters, even compared to seagrass in more pristine systems without excess nutrients,” he said. So he gathered as much historic data about the slough as he could find from other researchers—crab population numbers, sea otter diet data, nutrient levels, and more—and it told a completely unexpected story.
He found that the species that were primarily in control of the slough habitat prior to the arrival of the sea otters were crabs, especially the large number of rock crabs. As they crawled along on the muddy floor of the slough, they ate most of the num
erous bottom-feeding invertebrates, including a sea slug called the California sea hare, which feeds primarily on algae. Without these grazing invertebrates around to eat the algae off the eelgrass, the eelgrass became suffocated. But when the otters arrived in the slough in the 1980s, the crab population declined, the invertebrate population increased, and the eelgrass began to get healthier. During those few years in the 1990s when the otters left the slough again, the whole process began to reverse itself—the crabs gained in numbers, the invertebrates declined, and the algae smothered the eelgrass. Now that the otters have returned in even bigger numbers and are staying around all year, the eelgrass is the healthiest it has been in quite some time.
This four-level cascade—from sea otters to crabs to algae-grazing invertebrates to eelgrass—has turned Elkhorn Slough’s eelgrass beds into the healthiest of any estuary on the West Coast. And it is all because Elkhorn Slough is the only estuary on the West Coast that has a population of sea otters. There are plenty of other tidal estuaries that are undergoing expensive eelgrass restoration efforts and could benefit from the animals. Many, including the entire San Francisco Bay area, have archaeological evidence of historic populations of otters prior to the fur trade. Tinker said these estuaries may, over time, become vitally important as sea otters expand their range north and south. “Sea otters have improved the health and abundance of eelgrass beds in a way that no one in a million years would have predicted,” he said. “And the only way we ever would have found it was to study it as it happened. All of a sudden we have another keystone story in a totally different environment, one that no one saw coming.”