Marching ahead with ocean conservation science

For nearly 34 years, Monterey Bay Aquarium has harnessed the power of science to guide every aspect of our work—exhibit development, public policy and outreach, sustainable seafood solutions, research and education programs. In 2017, the Aquarium became one of the first 100 partners to support the first March for Science as a way to share our dedication to the scientific process. As the 2018 March for Science ramps up on April 14, we thought we’d revisit some of our greatest moments in marine conservation science over the last year. In these, and many other ways, we’re harnessing the power of science to make our world a better place.

Dynamic tuna dorsal fins

Researchers discovered Pacific bluefin tuna can move their dorsal fins with an internal hydraulic mechanism that aids in fast swimming and quick turns

While observing Pacific bluefin tuna inside the Tuna Research and Conservation Center (TRCC), scientists noticed something…fishy about the way they were swimming. TRCC scientists logged hours of video footage and, after conducting routine medical exams, discovered that the dorsal fins of tunas move both forward and backward as they swim—especially when they hunt for prey in quick flashes of speed. Their work, reported in a cover article published in Science magazine, documented that the team of scientists discovered a hydraulic mechanism that allows a tuna to articulate its dorsal fin along a range of angles depending on which behavior the tuna exhibits.

Sea turtles use flippers like fingers

Sea turtles use their flippers in a multitude of ways to help them capture prey, like this green turtle in the Gulf of Thailand that’s grasping a jelly before it eats. Photo © Rich Carey/

When evolution, animal behavior and body form meet in one elegant space, we call it “ecomorphology,” an area of expertise for Aquarium senior research biologist Jessica Fujii, who for years has studied how and why sea otters use tools. But when Jessica and her colleagues observed that sea turtles use their flippers like tools to swipe, slice and corral their food, we might call that “evolutionary serendipity”—something that sea turtles did not necessarily evolve to do, but do anyway. In a recent study published in PeerJ and led by Jessica, we learned that sea turtles use their flippers, largely designed for locomotion, to manipulate their prey. The scientists tapped crowdsourced images and videos from around the world to document turtles prying open scallops and karate-chopping jellyfish, confirming that this ancient marine reptile need not have a frontal cortex to perform such complex maneuvers. Because transparency is a key tenet of scientific inquiry, our team decided to make both the paper and the peer reviews of the paper available free to anyone with internet access.

Museum feathers reveal seabird diet changes

Some of the feathers in the study were from seabirds collected in the 19th century by groups like this 1885 party that landed in the Northwest Hawaiian Islands. The specimens are archived at the Bishop Museum in Hawaii. Photo courtesy Bishop Museum.

Naturalists hiking around the islands of Hawaii in 1890 could never have guessed that the seabird feathers they collected would someday be used to help tell the story of a changing ocean. But for Aquarium researcher Tyler Gagne, lead author on a new study of how seabird diets have changed over the last 130 years, the feathers played a vital role in reconstructing what seabirds have—and have not—been eating. Using stable isotope analysis, Tyler and his team traced specific chemical signatures found in the preserved seabird feathers to show how, over time, eight different species in the North Pacific have shifted from fish to squid, a transition that suggests both human and climate impacts are influencing their dietary choices.

The data behind sea otter rescues

White shark bites are causing the majority of sea otter deaths at the edges of the otters’ range. Photo courtesy MBAPhoto © Nicole LaRoche, U.S. Geological Survey

For more than 30 years, sea otter researchers and animal care specialists at the Aquarium have been tagging, tracking, rescuing and rehabilitating stranded adult sea otters and pups. The data collected from 725 live strandings between 1984 and 2015 provide an intricate portrait of major threats California sea otters face as their population slowly recovers. Aquarium researchers determined that the absence of significant kelp canopy coverage at the peripheries of the sea otter range, especially in waters north of Santa Cruz and south toward Point Conception, can inhibit sea otters’ ability to reproduce and survive. Without sufficient kelp  cover, sea otters, especially reproductive females and their pups, can be left vulnerable to shark bites.

Young white sharks: the wonder years

Juvenile white shark swims at the surface of Bahia Sebastian Vizcaino. Photo courtesy CICESE.

After years of studying the underwater lives of white sharks, Aquarium researchers and their partners in the United States and Mexico noticed some missing links in the life history of these apex predators. Where do white sharks give birth, and where do their pups grow up? Thanks to a study published in Fisheries Research, scientists discovered that Bahia Sebastián Vizcaino, a warm lagoon on the coast of Baja California, is a nursery for newborn white sharks. This study formalized a de facto understanding that southern California was the place to find young white sharks, but researchers validated a more surprising fact about juvenile white sharks: they don’t stay in Californian waters and they regularly travel to Mexican waters and back again.

These are just a few highlights reflecting the growing scope of ocean science taking place at the Aquarium. We’ll continue to conduct new science every day, to inspire new generations of science-literate citizens, and to use the best-available science to inform everything we do to assure a bright future for our ocean planet.

—Athena Copenhaver

Learn how we use science to support ocean policy, address plastic pollution and climate change, protect marine wildlife and ecosystems, and promote sustainable global fisheries and aquaculture.

Our best Conservation & Science stories of 2016

It’s been an exciting year for ocean conservation at the Monterey Bay Aquarium.

We’ve shared how our care for the animals in our living collections—including snowy ploverscomb jellies, ocean sunfish and Pacific seahorses—contibutes to the conservation of their wild kin.

The Aquarium helps rehabilitate threatened Western snowy plovers.

We’ve visited the Canadian cousins of Monterey Bay’s sea otters, explored how sea otters use tools, and assisted scientists working to decode the sea otter genome.

We’ve collaborated with our colleagues in Baja, Mexico on a number of conservation missions—one of them involving ancient shark mummies. And we joined forces with U.S. aquariums and zoos to call for stronger protections for the endangered vaquita porpoises of the Gulf of California.

As 2016 comes to a close, let’s look back at the top 10 highlights from this blog:

White shark GIF_MBA
A white shark approaches schooling sardines.

10. Camera to Crack a White Shark MysteryOur senior reseach scientist teamed up with the Monterey Bay Aquarium Research Institute for a high-tech mission: to capture video footage of great white sharks in their most mysterious habitat.

“Some of the engineering team said it was an impossible job,” MBARI Engineer Thom Maughan recalled. “But I’m attracted to those opportunities.”

Continue reading Our best Conservation & Science stories of 2016

Sea otters are handy with tools

What makes people different from other animals? Scientists used to think the ability to make and use tools was a distinguishing characteristic. That changed in the 1960s, when Jane Goodall observed chimpanzees using sticks to fish termites out of mounds. Now, crows, dolphins and sea otters make the short list of creatures that use tools.

Sea otters dive in shallow coastal waters to collect hard-shelled prey like sea urchins, mussels, abalones, clams and snails. Some shells, like the calcium carbonate armor that protects snails, are harder to crack than others—so otters sometimes use rocks as anvils to break them open.

Continue reading Sea otters are handy with tools

Decoding the sea otter genome

Sea otters play a critical role in the health of coastal ecosystems. But we’re not seeing all the benefits because their numbers have yet to recover from the impact of the fur trade that ended more than a century ago. Now there’s a new tool to aid in sea otter recovery: a first-ever sequencing of the sea otter genome.  Annabel Beichman, a PhD student in UCLA’s Department of Ecology and Evolutionary Biology is leading the effort and shares the progress – and the Monterey Bay Aquarium’s key role in the project. 

Large sea otter populations once ranged from Northern Japan all the way around the Northern Pacific Rim to Baja California. All that changed starting in 1741 when the Bering Expedition shipwrecked in the Commander Islands. Vitus Bering and most of the crew perished, but a handful of survivors returned to Russia, bringing with them sea otter pelts and stories of abundant sea otter and fur seal populations to the northeast.

Sea otter hunters in Coos Bay, Oregon, 1856. Courtesy Oregon History Project
Sea otter hunters in Coos Bay, Oregon, 1856. Courtesy Oregon History Project

This spurred a mad rush to obtain sea otter pelts that drove sea otter populations nearly to extinction by the end of the 19th century.

In 1911 sea otters were protected by the International Fur Seal Treaty. But for many of the small, isolated populations that remained it was already too late. They were down to fewer than 100 individuals in each fragmented pocket, and in many cases – in British Columbia, Canada and Baja California – they vanished over time.

Long, slow recovery

In the Kuril Islands, Kamchatka Peninsula, Aleutian Islands, South-Central Alaska and California, however, the small remaining populations began to grow. Several returned to their historical population sizes over the course of the 20th century. In California, the population has recovered more slowly, to around 3,000 adults and dependent pups – well below the level that existed before the fur trade.

Sea Otter Genetic BottleneckDecimation of sea otters led to what’s known as a “population bottleneck”. This occurs when a population experiences an extreme decline to a very small size, followed by a re-expansion. A handful of individuals emerge on the other side of the bottleneck and all future members of the population are the descendants of that lucky handful.

The bottleneck can have long-lasting genetic consequences, because the population has lost much of the genetic diversity that once existed and is subject to harmful genetic mutations that can become commonplace in the population. These mutations can impact individuals’ ability to withstand disease, reproduce or survive into adulthood.

Mapping otters’ genetic code

Today, society is in the middle of a revolution in genome sequencing (the sequencing of all the DNA building blocks that make up an individual’s entire genetic code: the unique blueprint that makes them what they are). Sequencing an entire genome used to be an impossible feat, and then impossibly costly. Now, thanks to major advances in technology, it’s possible to map the genetic profile of any organism, at a relatively modest cost.

The first blood sample will come from a Monterey Bay Aquarium exhibit otter. Photo courtesy USGS.
The first blood sample will come from a Monterey Bay Aquarium exhibit otter. Photo courtesy USGS.

We’re now in the process of sequencing the first-ever sea otter genome. We’re using a blood sample from a resident sea otter at the Monterey Bay Aquarium, kindly supplied by the aquarium’s veterinarian, Dr. Michael Murray. (He has himself studied sea otters throughout their range: on Russia’s Kamchatka Peninsula, in Alaska and throughout the Pacific Northwest.)

We’re thrilled that the first sea otter genome will come from an animal that you can visit – a living reminder of the way in which genomics and conservation biology can come together to provide new insights into a remarkable species.

Insights into the population

This first genome will provide a template for the sequencing of an additional 60 genomes from across the sea otter range. Sequencing and assembling the first genome for a species represents a huge technical and computational effort. Once it’s complete, sequencing genomes from additional individuals is straightforward.

Genes from 60 individual sea otters will be sequenced as part of the project. Photo © Jim Capwell.
Genes from 60 individual sea otters will be sequenced as part of the project. Photo © Jim Capwell.

The first genome (known as the “reference” genome) has to be sequenced very deeply (many overlapping sequences of each part of the genome), before we use complex computer algorithms to assemble the sequences into one big genome. Subsequent  genome sequences can be “mapped” to the reference template, rather than having to be assembled from scratch each time.

A single genome by itself provides a lot of information about a species’ evolution. To understand more about past population size changes, specific adaptations, or levels of harmful genetic variation in the genome, you need many more individuals’ genomes. That’s why, once we have the reference genome assembled, we’ll be sequencing the genomes of 10 individuals from each of six remnant populations.

Changes through time

This huge dataset will let us look for special adaptations that allow sea otters to live in the marine environment. Genome sequencing will also tell us how sea otter populations have changed in size through time, and will let us understand how the fur trade population bottleneck has affected modern sea otters’ genomes.

Ancient DNA from bones in midden sites like this in California's Channel Islands will be sequenced, too. Photo © National Park Service
Ancient DNA from bones in midden sites like this in California’s Channel Islands will be sequenced, too. Photo © National Park Service

We aren’t going to stop at merely sequencing modern genomes from living sea otters. Recently, there have been major developments in sequencing “ancient DNA” – DNA from individuals that died long ago. For example, scientists have sequenced a Neanderthal genome and the genome of an ancient horse that lived before horses were domesticated. Many other ancient genomes have been completed and others are on the way.

Our lab will sequence genomes from pre-fur trade sea otter specimens recovered from Native American and First Nations midden sites, to compare sequences from before and after the bottleneck. This will let us directly compare how the abundance of harmful mutations has changed over time, and see whether modern otters have an increased burden of harmful mutations compared to their ancestors.

A boost for recovery efforts

Genome sequencing has practical applications to efforts to recover sea otter populations throughout their range – efforts to which Monterey Bay Aquarium researchers are contributing in significant ways. The genetic information will be incorporated into sea otter conservation plans – to identify populations that may be more vulnerable to disease and catastrophe because of past small population sizes and isolation, and to determine if populations would benefit from introduction of animals with different genetic profiles, perhaps from geographically distant sub-populations that don’t currently interbreed.

Understanding the genetic history of sea otters could advance recovery efforts. Photo © Jane Vargas-Smith
Understanding the genetic history of sea otters could advance recovery efforts. Photo © Jane Vargas-Smith

Like all recovery efforts on behalf of sea otters, our work involves collaboration among many partners; in this case UCLA, UC Santa Cruz, the Smithsonian Conservation Biology Institute and the Monterey Bay Aquarium. We have sea otter experts, genomics experts and conservation genetics experts on board so that we can make the best use of this unprecedented level of genomic data from living sea otters and ancient populations.

We have a lot to learn! We’ll share what we find as the project progresses.

Learn more about the sea otter genome project.

Sea otters and abalone: A special synergy

Decades of conservation work have brought southern sea otters back from near-extinction. This year, their numbers topped 3,000 for the first time since fur traders decimated the population in the 19th century. But as the animals move into new territory along the California Coast, they’re encountering another food source: endangered black abalone.

Fishing groups have worried that sea otters may keep abalone from rebounding—and dashing their chance of reopening a commercial abalone fishery in California. But last month, a paper published in the scientific journal Ecology found the recovery of sea otters doesn’t prevent the recovery of black abalone. In fact, the two species benefit one another.

It’s complicated

The paper, authored by University of California, Santa Cruz Professor Peter Raimondi with researchers from the University of California, Davis and the U.S. Geological Survey, investigated abalone populations in 12 places along the Central Coast—some with otters, some without.

Illustration of black abalone, Haliotis cracherodii. © Monterey Bay Aquarium

If otters were harming abalone populations, the researchers reasoned, there would be fewer abalone where there were more otters. Instead, the data showed exactly the opposite pattern: Where there are more otters, there are more abalone.

The result may not be intuitive, but that reflects the complexity of ocean ecosystems. Raimondi and his colleagues aren’t quite sure why otters and abalone benefit one another, but they have some ideas.

First, both species thrive in the same habitat: rich kelp forests over rocky bottoms. And second, while abalone are food for sea otters, otters may also provide food for abalone. Sea urchins, a staple of the otter diet, can wipe out kelp forests, leaving very little food for other animals.

By keeping urchin populations in check, otters improve the health of kelp forests, indirectly giving abalone more to eat.

A holistic approach

Foraging otter
A territorial male sea otter in Moss Landing uses his paws to forage for shore crabs in the pickleweed, leaving his eyes free to monitor his surroundings. Photo by Lilian Carswell/USFWS.

Lilian Carswell, Southern Sea Otter Recovery Coordinator for the U.S. Fish and Wildlife Service, isn’t surprised by the finding. “People are beginning to recognize that otters have a variety of effects that we hadn’t really appreciated,” she says.

Scientists have long suspected healthy abalone and otter populations might benefit one other. In 2012, David Jessup, former director of the Marine Wildlife Veterinary Care and Research Center in Santa Cruz, pointed out that otters and abalone coevolved as predator and prey over hundreds of thousands of years.

“It would be extremely disadvantageous to sea otter survival if they could drive abalone to rarity or extinction,” he wrote in a 2012 post on “It would be a remarkable evolutionary failure.”

The population decline that prompted officials to list black and white abalone under the Endangered Species Act in 1997 had nothing to do with sea otters, Jessup added. At that time, there were still too few otters in the wild to affect the abundance of abalone. Instead, a combination of overfishing and a fatal disease called withering syndrome caused abalone numbers to plummet.

Black abalone2
Abalone under water in rocky shore tidepool. ©Monterey Bay Aquarium, photo by Kathleen Olson.

There’s been a long-term misunderstanding about abalone population levels, Carswell adds. In the early 20th century, she explains, California settlers found enormous piles of shellfish up and down the coast. They assumed this incredible abundance was the norm, and abalone fisheries sprang up to take advantage. But scientists now know the unusually high numbers of abalone and other shellfish were due to the absence of otters.

“The [abalone] baseline was already very skewed, totally out of whack, because otters had been removed,” Carswell says.

Andrew Johnson, the Aquarium’s Sea Otter Research and Conservation manager, says people enjoyed the abalone harvest for decades in the absence of sea otters. “It was unregulated, they overexploited it, and they got their benefit from it,” he says. “But now things are coming into a better balance.”

A perfect pairing

In the long term, Raimondi’s paper suggests, both abalones and otters can thrive along the California coast.

Relationships between animals are complex, and ecosystem management works best when scientists and managers take multiple species into account. In contrast to the old idea that otters reduce abalone numbers, Raimondi’s study suggests an important synergy between the two species.

As sea otters recolonize their historical range, they improve ecosystem health. Johnson hopes the paper will inspire productive conversations, helping abalones and sea otters recover together.

-Diana LaScala-Gruenewald

Learn more about our sea otter conservation research.

Sea otters and eelgrass, in one infographic

Long-term observations by our sea otter scientists confirm that sea otters are transforming the Elkhorn Slough estuary, in positive ways, by devouring predators that keep eelgrass beds from thriving. We’ve told the story before, in words and pictures. For Sea Otter Awareness Week, we’ve created a simple infographic to document the relationships. You can read more on the aquarium’s general interest Tumblr blog.  Otter eelgrass infographic

Conservation tip: Give sea otters space

Kayakers looking to get up close and personal with sea otters – and maybe snag a selfie – may unintentionally be causing harm to these beloved (and threatened) marine mammals.

When approached directly by people in the wild, sea otters often feel threatened and may dive or swim away to avoid them. This evasive maneuver can cost sea otters precious energy – energy they can only recoup by spending less time resting and more time hunting and eating.

Because portions of sea otter habitat are already at their carrying capacity, making up the lost calories can be challenging at best. and life-threatening at worst. It’s an especially big problem for nursing mother otters who are already energetically stressed by the burden of pup rearing.

In honor of Sea Otter Awareness Week, we’re bringing attention to this often-overlooked area of citizen stewardship.

Approaching too close to sea otters is both bad for their health and a violation of federal law. Photo courtesy
Approaching too close to sea otters is both bad for their health and a violation of federal law. Photo courtesy

Kayakers and other ocean goers like swimmers and paddleboarders likely don’t know that they’re putting sea otters at risk when they get too close, says Gena Bentall, the program coordinator of Be Sea Otter Savvy, a collaborative effort by the aquarium, U.S. Fish and Wildlife Service, California Department of Fish and Wildlife and Friends of the Sea Otter to raise awareness of sea otter disturbances by tourists.

“The cuteness of sea otters is their own detriment in a way,” Gena says. “People aren’t really going to try to approach a less charismatic species. They’re essentially loving them to death by getting too close.”

Diving to avoid people in watercraft exacts a an especially heavy toll on nursing mother sea otters. Photo: Randy Wilder
Diving to avoid people in watercraft exacts a an especially heavy toll on nursing mother sea otters. Photo: Randy Wilder

While the occasional run-in may seem trivial, a single sea otter may be forced to evade people several times a day. Gena said the cumulative effect of chronic disturbances can spell “death by a thousand cuts” for some sea otters.

According to Monterey Bay National Marine Sanctuary officials, wildlife disturbance of sea otters and other animals represents more than 40 percent of all violations recorded each year. (Disturbing sea otters and other marine mammals is a violation of federal law.)

Gena and her team are trying to quantify just how much these disturbances are costing sea otters, while also getting the word out about how to safely observe otters –  from a reasonable distance.

Gena, a kayaker herself, said one of the major problems is that kayakers know too little about the consequences of approaching ocean wildlife. One major step is to have kayak rental outfits provide educational materials to all their customers. She praised one local outfitter that educates its customers in responsible behavior around the wildlife they might encounter, including putting stickers on its rental boats with tips on how to observe sea otters respectfully.

I's possible to observe sea otters and other wildlife, and maintain a respectful distance. Photo courtesy Frank Steube.
It’s possible to observe sea otters and other wildlife, and maintain a respectful distance. Photo courtesy Frank Steube.

Be Sea Otter Savvy is concentrating its public awareness efforts on three hot spots where they’ve observed the most disturbance of sea otters: Elkhorn Slough in Moss Landing, Cannery Row, and Morro Bay in San Luis Obispo County.

“Our goal is to not scold people or shame people,” Gena says. “We’d rather get them to pay attention to wildlife, think about the ramifications of their behavior, and to have empathy for the animals.”

Be Sea Otter Savvy is looking for volunteers, particularly in San Luis Obispo County, to help monitor sea otter behavior and activity relative to marine recreation activities.

The best thing to do when out on the water, Gena says, is to keep your distance from sea otters as much as possible. When approaching, she adds, it’s better to float the kayak or paddleboard parallel to the animal from a safe distance, instead of paddling directly at them – a maneuver the otter may interpret as threatening. She also suggests putting the camera phone down and just being in the moment.

Cynthia McKelvey

Learn what we’re doing to help California’s threatened sea otter population recover.

Sea otter numbers are up. So, what does it mean?

The California sea otter population in 2015 has reached its highest level since fur traders hunted otters to near-extinction in the 19th century. But prospects for recovery of the threatened species are much more complicated than the numbers imply.

A recent spike in sea urchins, a favorite prey item for sea otters, may be partly responsible for this year’s higher count, according to U.S. Geological Survey (USGS) researchers. At the same time, there’s growing concern that bites from white sharks are killing high numbers of sea otters at the northern and southern ends of their range – precisely the areas where the population must grow to expand into historic sea otter habitat along the California coast.

By eating sea urchins and other grazing animals, sea otters allow kelp forests to thrive. Photo by Neil Fisher
A spike in the sea urchin population may have contributed to this year’s rise in sea otter numbers. Photo by Neil Fisher

“There’s much more to the story here than the main finding would suggest,” cautions Dr. Tim Tinker, a research ecologist who leads the USGS sea otter research program, in collaboration with the Monterey Bay Aquarium sea otter team and other colleagues. “We’re looking into various factors that may be affecting the survey results.”

In 2015, the three-year average of the population reached 3,054 animals. Under the current federal recovery plan, to be considered for removal from threatened status, the average sea otter count must be more than 3,090 animals for three consecutive years.

Even if they come off the threatened species list, sea otters would be safeguarded as a depleted species under the Marine Mammal Protection Act. The recovery plan estimates at least 8,400 animals represents the lower end of an “optimum sustainable population” in California.

Sea otter in kelp-USGS-
Sea otters play a vital role in maintaining the health of coastal kelp forest ecosystems. USGS photo by Benjamin Weitzman.

“Seeing the population increase is encouraging, but we believe success will only come when we have a fully recovered and sustainable population of sea otters as part of a healthy marine ecosystem along the entire California coast,” says Andrew Johnson, the aquarium’s sea otter program manager.

For more than 30 years, our research program has worked to understand the critical role sea otters play in the health of coastal ecosystems, in California and throughout the sea otters’ range around the Pacific Rim. Sea otters have long been recognized for their vital role in restoring and maintaining healthy kelp forests. Now we and research colleagues are learning that they’re doing the same in coastal wetlands.

In addition to our research program, we’re actively working to support policies that protect and restore coastal habitats that this iconic keystone species depends on for its recovery.

Sea otter mom and pup in Elkhorn Slough: Photo: Randy Wilder
Sea otter mom and pup in Elkhorn Slough: Photo: Randy Wilder

Along with conducting the annual population survey, USGS scientists annually update a database of sea otter strandings: the number of dead, sick or injured sea otters recovered along California’s coast. In 2014, scientists from the California Department of Fish and Wildlife, USGS, the aquarium and other institutions recovered or documented 386 stranded sea otters.

These data are shedding new light on sea otter population ecology along different parts of the coast. For example, a high proportion of sea otter carcasses recovered between Cayucos and Pismo Beach in recent years have white shark bite wounds – a potential explanation for the downward trend in sea otter numbers in that area.

“Before the early 2000s, we didn’t see very many shark-bitten otters south of Monterey,” says Mike Harris, a biologist with the California Department of Fish and Wildlife. “Shark bite cases now explain about 70 percent of the total strandings in this area.”

Sea otter research by governmental agencies in California is funded in part through voluntary contributions by taxpayers when they file state income tax returns. The fund was inspired by a legislator’s family visit to our sea otter exhibit in 2005. To date, it has generated more than $2.7 million for sea otter field studies and other recovery efforts.

Learn more about our sea otter work.

Read details about the 2015 population survey.

Photo of sea otter raft in Elkhorn Slough © Jane Vargas-Smith.

Kristen Weiss: Sea otters, kelp and ocean tipping points

Through September 2, Monterey Bay Aquarium and Monterey Bay National Marine Sanctuary are hosting Big Blue Live – an unprecedented series of live natural history broadcasts from PBS and the BBC. Big Blue Live highlights the remarkable marine life that gathers in Monterey Bay each summer, and celebrates an ocean conservation success story of global significance. We’re publishing guest commentaries about conservation efforts that contribute to the health of the bay and our ocean planet. This is from Kristen Weiss, an early career science fellow at the Center for Ocean Solutions. The Center is a collaboration among the Stanford Woods Institute for the Environment and Hopkins Marine Station of Stanford University, the Aquarium and the Monterey Bay Aquarium Research Institute.

Kristen Weiss
Kristen Weiss

The story of sea otter loss and recovery has had dramatic consequences for the health of Monterey Bay’s kelp forests. Less than 100 years ago, sea otters were thought to be extinct along the California coast as the result of rampant overhunting by fur traders. While otter hunting was officially banned in 1911, there seemed little hope of recovery at the time.

Then, in 1938, a small population of otters was discovered off the Big Sur coast just south of Monterey. Since then, sea otters have made a modest comeback (about 3,000 individuals) thanks to their protected status.

A remnant colony of sea otters was rediscovered off the Big Sur coast in the 1930s. Photo © William L. Morgan/California Views Photo Archives
A remnant colony of sea otters was rediscovered off the Big Sur coast in the 1930s. Photo © William L. Morgan/California Views Photo Archives

They’re now a common sight in the Monterey Bay National Marine Sanctuary where they have helped catalyze the regrowth of kelp habitat. As Dr. Steve Palumbi of Stanford University’s Hopkins Marine Station writes in his book The Death and Life of Monterey Bay, once otters recolonized Monterey Bay “they fed happily on sea urchins, and they left luxuriant kelp forest growing in their wake.”

Kelp Forests reach a tipping point

In nature, one plus one does not always equal two. Sometimes, small changes in human pressures or environmental conditions can result in disproportionately large responses in the ecosystem – potentially even collapse. Ecosystems can respond to stressors in nonlinear ways, displaying ecological thresholds (also known as “tipping points”) beyond which systems undergo dramatic change. The Center for Ocean Solutions is a collaborator in the Ocean Tipping Points project that aims to understand and predict where ecological thresholds might exist in marine habitats such as kelp forests.

By eating sea urchins and other grazing animals, sea otters allow kelp forests to thrive. Photo by Neil Fisher

As was the case in Monterey Bay, the loss of sea otters typically marks an abrupt tipping point for kelp forest habitat. As a keystone species, otters maintain kelp habitat by eating sea urchins, the main consumers of kelp. In the absence of otters, urchin populations can grow unchecked, their out-of-control grazing undermining kelp forests and creating “urchin barrens” devoid of the shelter and biodiversity that kelp ecosystems typically offer. Where kelp once harbored diverse assemblages of juvenile and adult fishes, invertebrates like urchins and shellfish now dominate a simplified habitat.

When such tipping points occur, the distribution of ecosystem benefits to humans can shift considerably. For example, kelp habitats support important commercial fish species and attract diving and snorkeling tourism. However, in the absence of otters, urchin fishermen often gain substantial benefits and may be opposed to management interventions aimed at otter reestablishment. These types of trade-offs highlight the difficulty of balancing social and ecological values in marine management.

 To help managers address social and ecological complexity, Ocean Tipping Points project collaborators have outlined seven principles for managing ecosystems that are prone to tipping points (see infographic below), so that managers can better predict and prevent unwanted tipping points.

Hope for sea otters in Monterey Bay

In Monterey Bay, marine managers, scientists, and conservationists are working to promote sea otter recovery through research and active management. The Monterey Bay Aquarium’s Sea Otter Program has been active for over 30 years, conducting important research on sea otters as well as caring for injured or stranded otters. To maintain healthy populations of otters, we need healthy marine environments.

The seven principles of managing for tipping points, applied to the kelp forest ecosystem. (Graphic by Jackie Mandoski and Courtney Scarborough)
The seven principles of managing for tipping points, applied to the kelp forest ecosystem. (Graphic by Jackie Mandoski and Courtney Scarborough)

At the Center for Ocean Solutions, researchers are working on projects such as the Kelp Forest Array and Environmental DNA to collect important information about water quality and species biodiversity in kelp forest habitat. These projects are helping identify what human-caused and natural threats may be impacting the bay so that we can better protect sea otter habitat into the future.

The expansion of sea otters along the Monterey coastline “left behind a string of changed shorelines and restored bay,” writes Palumbi. “Where there was once subtidal rock bristling with urchin spines, there now bloomed kelp forest with sea urchins and abalone restricted to crevices in the rock. Where kelp bloomed, there now thrived a bustling community of fish and invertebrates.”

While sea otters still have a long way to go to reach numbers comparable to historical population sizes, their initial recovery along California’s central coast  and the related comeback of healthy kelp forest habitat here in Monterey Bay – offers hope for other species and regions affected by significant human activity.

Learn how the Center for Ocean Solutions is tackling major challenges to ocean health.

Sea otter insights: monitoring apex predators in Elkhorn Slough

Michelle Staedler stands atop a hill above Elkhorn Slough. It’s low tide – low enough to see the green eelgrass just under the surface of the water. Michelle peers through a spotting scope with a directional radio antenna attached. Static hums on the radio until it’s broken by a quiet blip…blip…blip coming from a radio tag inside the abdomen of a sea otter. Michelle records the time and notes that the otter she’s been watching for the last fifteen minutes, 501, has come up with a clam that she shares with her pup, floating by her side.

Michelle Staedler with the  Sea Otter Program at Monterey Bay Aquarium, monitors the behavior of sea otters in Elkhorn Slough. Photo by Cynthia McKelvey
Michelle Staedler with the Sea Otter Program at Monterey Bay Aquarium, monitors the behavior of sea otters in Elkhorn Slough. Photo by Cynthia McKelvey

Michelle is recording foraging data on Otter 501, perhaps the most famous sea otter in the  history of the Monterey Bay Aquarium’s otter surrogacy program. Rescued as a pup by the Aquarium and raised in captivity, she was successfully released in 2011 into Elkhorn Slough, a major estuary system in Moss Landing that feeds into Monterey Bay. Otter 501 has gone on to raise several pups of her own in the slough, where many of her species have come to flourish.

Michelle and her collaborators at the U.S. Geological Survey and the Elkhorn Slough National Estuarine Research Reserve have been counting otters in the slough since September 2013 as part of a population monitoring project. She has conducted several research projects on sea otter behavior since she began working with the Aquarium nearly 30 years ago. Her work focuses on sea otter mothers, their pups and how they feed. Foraging data gathered in the slough has proven particularly useful to ecological research.

Crabs are a favorite prey item for sea otters in Elkhorn Slough. By eating the crabs, otters help restore the health of the slough ecosystem. (Photo by Ron Eby)
Crabs are a favorite prey item for sea otters in Elkhorn Slough. By eating the crabs, otters help restore the health of the slough ecosystem. (Photo by Ron Eby)

Sea otters are a keystone species – central to the overall health of ecosystems of which they’re a part. Like other top ocean predators, their presence helps maintain a diverse community of animals and plants. The web can unravel if otter numbers dwindle. That’s exactly what happened when they were hunted to near-extinction by fur traders in the 18th and 19th centuries.

In kelp forests, otters eat sea urchins and other grazing animals, keeping them from devouring the kelp. This allows the productive ecosystem to thrive.

Using several data sets, including Michelle’s extensive foraging data, researchers at the University of California, Santa Cruz discovered that otters play an equally important role in the slough.

The sea slug Phyllaplysia taylori, also known as the "eelgrass sea hare," feeds on algae growing on the leaves of eelgrass. (Photo by Brent Hughes)
The sea slug Phyllaplysia taylori, also known as the “eelgrass sea hare,” feeds on algae growing on the leaves of eelgrass. (Photo by Brent Hughes)

As the story goes, before the otter population bounced back in the mid-1980s, eelgrass beds in the slough were being smothered by algae that grew unchecked on the leaves, absorbing the sunlight eelgrass needed for photosynthesis. In a healthy ecosystem, snails, slugs and other invertebrates would eat the film of algae, cleaning the grass and allowing it to get the sunlight it needs. But those grazers were being devoured by crabs, which had few natural predators in the slough – that is until sea otters turned up and began gobbling up the crabs.

Brent Hughes, who led the UC Santa Cruz research team, said he couldn’t have cinched his conclusion without the help of Michelle’s data.

“In the slough, we have unprecedented coverage of what a top predator is doing in terms of the ecology of a system, the behavior, exploitation of resources and habitat use,” Brent said. “It’s pretty much unprecedented in the marine ecology world, and that’s because of all the work that Michelle and [Brent’s collaborator] Tim Tinker have been doing.”

It’s important that she and her colleagues continue to monitor the otters, as well.

“We’re looking at the population of otters here,” Michelle explained. “How many are here, what areas of the slough they use, how they take advantage of micro habitats.”

For example, she said, a pioneer population of about 20 sea otters used to live around the jetty system in Moss Landing Harbor, at the mouth of the slough. Over time, their numbers ballooned to over 100 animals, and she’s observed them moving farther and farther up into the slough. Because of the significant restorative impact the otters can have on the ecosystem, it’s critical for researchers keep an eye on them to see what happens if their numbers continue to grow, Brent said.

– by Cynthia McKelvey


Hughes B.B., Eby R., Van Dyke E., Tinker, M.T., Marks, C.I., Johnson, K.S., Wasson K. (2013). “Recovery of a top predator mediates negative eutrophic effects on seagrass.” Proceedings of the National Academy of Sciences. 110(38).   15313–15318, doi: 10.1073/pnas.1302805110

Sea otter raft photo © Jane Vargas-Smith