Conservation & Science

The feel-good science behind sea otter surrogacy

Surrogate-reared otter released into Elkhorn Slough by Monterey Bay Aquarium
A new study reveals the Aquarium’s Sea Otter Program bolsters the local otter population. Here, a surrogate-reared otter leaps into Elkhorn Slough on California’s central coast.

Ask not (only) what you can do for sea otters, but what sea otters can do for California.

That’s one of the thoughts on the minds of Aquarium scientists in the wake of a new study, which confirms the power of sea otters to restore coastal ecosystems.

Since 2002, the Monterey Bay Aquarium has reared rescued sea otter pups for release to the wild. Female otters in our exhibit serve as their “surrogate mothers,” teaching them critical life skills like how to groom themselves and forage. The hope is that when the pups are released in Elkhorn Slough, a wetland 20 miles north of the Aquarium, they’ll be able to thrive on their own.

A newly published study confirms that these surrogate-reared pups are surviving as well as their wild kin—and the resulting bump in the otter population at Elkhorn Slough is helping to restore the estuary ecosystem.

The remarkable success of the Aquarium’s program, documented in Oryx, highlights a tremendous opportunity: to help sea otters contribute to the revival of other coastal estuaries along the California coast.

Otter 327 with surrogate mother Toola at Monterey Bay Aquarium
Otter 327 (right) was raised by surrogate mother “Toola” (left) at Monterey Bay Aquarium.

Historically hunted for their fur, southern sea otters were nearly wiped out in California in the 19th century. Thanks to federal protection and a concerted conservation program, the population has slowly recovered in recent decades. But California’s wild population has plateaued at just over 3,000 sea otters—far below the historical level of 18,000-20,000. As a keystone species, sea otters have earned the title of “ecosystem engineers,” because they can deliver outsized benefits to degraded stretches of coastline.

The Aquarium’s sea otter surrogacy program is the first of its kind—a pioneering approach to rescuing, rearing and returning sea otter pups to the wild. From 2002-2016, Aquarium staff released 37 surrogate-reared pups in Elkhorn Slough, a national estuarine research reserve. Scientists now estimate that those surrogate-raised otters and their wild offspring account for more than half of Elkhorn Slough’s otter population growth over the past 15 years.

 “The success of those individuals wound up having both population-level and ecosystem-level impacts,” says Karl Mayer, sea otter field response coordinator at the Aquarium and lead author of the new scientific study. “This lays the groundwork for a new discussion around returning sea otters to more of their historical range.”

“We knew this was a great program and a feel-good story,” Aquarium Chief Scientist Dr. Kyle Van Houtan added. “Now we know this is great science.”

In need of a nudge

Before the onset of the fur trade, sea otters ranged from northern Japan through

Otter 327 in the wild with her own pup in Elkhorn Slough - credit Monterey Bay Aquarium
Surrogate-reared otter 327 (right) successfully returned to the wild where she raised her own pup.

Alaska and down the West Coast all the way to Mexico’s Baja California. But today, California’s sea otters are limited to a 300-mile stretch of the Central Coast, from around Santa Cruz to Santa Barbara. 

“In the center of their range, sea otter populations are dense and close to carrying capacity,” Karl says. “However, at the northern and southern edges, kelp is sparse—providing little shelter for otters to evade white shark bites. For the population to grow in a meaningful way, the range itself might need to expand into historical habitats to which sea otters have not yet returned. Through our surrogacy program, we may have figured out how to facilitate that expansion.”

In the 1960s and ‘70s, wildlife managers succeeded in several attempts to move sea otters from established territories to waters they inhabited before the fur trade. They helped sea otters return to Southeast Alaska, British Columbia and Washington state, but an effort to reestablish sea otters in Oregon failed.

 In California, translocation took a hit after more than 100 wild sea otters were moved to San Nicolas Island, 70 miles south of Ventura, starting in 1987. The effort was politically fraught and biologically unsuccessful. More than 80 percent of the translocated sea otters disappeared or swam back to the mainland. While the island’s sea otter population has grown in recent years (one estimate puts it over 80 animals), many still remember the translocation’s initial shortcomings.

Any new proposals to reintroduce sea otters to more of their historical range, Karl cautions, must consider the lessons of San Nicolas Island.

 Where to go from here?

Surrogate mother Abby with wild-born pup 598 in 2012 by Monterey Bay Aquarium
Surrogate mothers like “Abby” (left) help raise stranded pups that can eventually return to the wild.

When the Aquarium first started pairing exhibit otters with orphaned pups, the goal was not to help sea otters return to their historical range. The Aquarium team simply hoped the surrogate otter moms would have more success teaching these rescued pups than the humans who tried it before them.

The new research paper confirms that surrogate-reared pups survive at a rate comparable to that of their wild kin. Unlike the animals translocated to San Nicolas Island, these wild-released otters are accepting Elkhorn Slough as their home territory. 

“Typically, if a sea otter has an established home range, it’s going to want to move back to it,” Karl says. “I think that’s what we saw with the majority of the animals that were moved to San Nicolas. They tried to go back home.”

 By contrast, most of the surrogate-reared sea otters stayed put after they were released into Elkhorn Slough. Karl says that’s because they were “ecologically naive” when they got separated from their mothers. “They just hadn’t been alive long enough to establish a territory,” he says. “In many cases, they probably stranded the same day they were born.”

Surrogate-reared otter 451 released into Elkhorn Slough in 2009 by Monterey Bay Aquarium
Surrogate-reared otters (like study otter 451) released to the wild can help restore ecosystems along the California coast.

 The surrogate-reared otters’ lack of site fidelity, combined with survival and reproduction rates on par with their wild counterparts, makes reintroducing these animals elsewhere a concept worth investigating. 

Historically, estuaries along the entire California coast supported sea otter populations. Today, Kyle says, many of our state’s ecologically degraded estuaries could benefit from sea otters’ return. 

“Surrogate-reared females were among the first to produce pups in Elkhorn Slough,” he says. “The fact that they have no ecological memory of another home makes them better candidates for reintroduction to unfamiliar habitat.” 

Where and when that might happen remains to be seen. For now, the Aquarium is literally taking baby steps.


Fishing for genes via eDNA

Just as steelhead trout migrate from saltwater to freshwater and back, Environmental Sample Processors (ESPs)—first developed by the Monterey Bay Aquarium Research Institute (MBARI) for studies in the ocean—have been getting a lot of use in freshwater over the last five years.

Kevan Yamahara and Doug Pargett install a pump system downstream of a fish trap in Scott Creek. The pump system feeds water to an Environmental Sample Processor to sample the DNA of fish in the stream. Photo © 2019 MBARI/Kim Fulton-Bennett

This spring, MBARI’s ESP team installed an instrument to collect samples of “environmental DNA” from a coastal creek just north of Monterey Bay. Researchers will use these samples to track populations of threatened steelhead trout, endangered coho salmon, and invasive species in the creek.

In the process, they could help revolutionize environmental monitoring and fisheries management nationwide.

The research is a joint project of MBARI and the Monterey Bay Aquarium, with funding from the Arthur Vining Davis Foundations as part of their newly launched Environmental Engagement, Stewardship & Solutions program. The work is being carried out in collaboration with the National Oceanic and Atmospheric Administration (NOAA). It is part of MBARI’s continuing effort to provide scientific data with direct application for ocean and wildlife conservation. Read more…

El impacto profundo del micro-plástico

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(Subtítulos en español están disponibles)

Existe un vasto ecosistema que se extiende muy por debajo de la superficie del océano, en donde la luz es escasa, aumenta la presión y la vida toma formas que bien podrían parecer extraterrestres. Pero incluso ahí, un lugar que parece un mundo apartado de la sociedad humana, nuestra basura plástica se está acumula.

Los científicos del Acuario y del MBARI tomaron muestras de la contaminación por micro-plástico en las aguas profundas usando el vehículo operado remotamente Ventana. Foto: cortesía del MBARI

En el mar profundo, resulta desafiante estudiar dónde se acumula ese plástico y cómo afecta a los animales. Por ello, los científicos del Monterey Bay Aquarium en colaboración con nuestros aliados del Monterey Bay Aquarium Research Institute (MBARI) lanzaron un ambicioso proyecto.

Los resultados del estudio en el cual se examina el  micro-plástico en las aguas de la Bahía de Monterey, fue publicado el 6 de junio por la revista Scientific Reports.

“Hemos diseñado este estudio para dar respuesta a una brecha fundamental en nuestro conocimiento sobre el plástico marino una vez que este llega al océano” indica la autora principal Anela Choy, anteriormente investigadora del MBARI y actual profesora del Scripps Institution of Oceanography en San Diego.

Los investigadores del MBARI recolectaron larváceos y sus filtros mucosos de alimentación usando vehículos de comando remoto. Foto: cortesía del MBARI.

El equipo de investigación recolectó datos usando vehículos de comando remoto (ROV, por sus siglas en inglés) —submarinos robóticos diseñados por ingenieros del MBARI— para recolectar muestras de agua en profundidades de entre 200 y 600 metros (unos 650 a 2,000 pies).

También buscaron plástico en animales que cumplen importantes funciones en las redes alimentarias marinas: langostinos pelágicos y seres parecidos a los renacuajos llamados larváceos gigantes, que se rodean con nubes de mucosa cuya función es capturar alimento y, en ellos, los investigadores descubrieron plástico.

“Los problemas como este son extremadamente complicados. Para intentar descubrir la manera de resolverlos se requiere de muchas herramientas distintas,” —menciona Kyle Van Houtan, científico principal del Acuario, quien realizó el estudio en coautoría con Anela y otros nueve investigadores de diversos campos que abarcan desde Fisicoquímica hasta Ecología Marina—. Read more…

The deep impact of microplastic


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There’s a vast ecosystem stretching far below the ocean’s surface — one where the light dims, the pressure mounts, and life takes on forms that can seem downright alien. But even there, a place that seems a world apart from human society, our plastic trash is building up.

Scientists from the Aquarium and MBARI sampled microplastic pollution in the deep waters of Monterey Bay using the ROV Ventana. Photo courtesy MBARI

In the deep sea, it’s a challenge to study where that plastic accumulates and how it affects animals. So scientists at the Monterey Bay Aquarium and our partners at the Monterey Bay Aquarium Research Institute (MBARI) launched an ambitious collaboration.

The resulting study, which examined microplastic in the waters of Monterey Bay, was published June 6 in the journal Scientific Reports.

“We designed this study to answer a fundamental gap in our knowledge of marine plastic once it reaches the ocean,” says lead author Anela Choy, a former MBARI researcher and now a professor at the Scripps Institution of Oceanography in San Diego.

MBARI researchers collected larvaceans and their mucus feeding filters using its remotely operated vehicles. Photo courtesy MBARI.

The research team gathered data by using remotely operated vehicles (ROVs), robotic submarines designed by MBARI engineers, to collect water samples at depths from 200 to 600 meters (about 650 to 2,000 feet).

They also searched for plastic in animals with important roles in the marine food web: pelagic red crabs; and tadpole-like creatures called giant larvaceans, which surround themselves with clouds of mucus that capture food — and, as the researchers discovered, plastic.

“Problems like this are extremely complicated. To try and figure out how to solve them, you need a lot of different tools,” says Aquarium Chief Scientist Kyle Van Houtan, who co-authored the paper with Anela and nine others, tapping fields from physical chemistry to marine ecology. Read more…

Clash of the titans: white sharks vs. orcas

When orcas and white sharks cross paths, only one can prevail as the true apex predator. New research from the Monterey Bay Aquarium published in Nature Scientific Reports details these rare, sometimes brutal encounters — and their ecological implications.

A new study illustrates what happens when orcas and white sharks encounter each other in the wild. Photo © Jim Capwell/

It’s a study decades in the making because observations of the two creatures interacting is a rarity.

Scot Anderson, a white shark expert and seasonal researcher for the Aquarium, still remembers one such run-in more than 20 years ago near the Farallon Islands, a short boat ride west of downtown San Francisco.

“The first time it happened was kind of shocking to everybody,” Scot says. “Before we had seen anything like that, people would ask, who’s the baddest predator?”

White sharks are seasonal visitors to the Farallon Islands, where they prey on elephant seals and other pinnipeds. Photo courtesy NOAA

The first scorecard came on October 4, 1997, when orcas killed and partially ate a white shark within view of a whale-watching boat. Scot was heading out from nearby Bolinas when he heard what was happening over the radio.

“We just went straight there,” he says. “We got there right as it was finishing. I saw the two orcas sticking their heads out of the water and squealing like they do when they have a kill. And the shark just sank away.” Read more…

Connecting historical tortoiseshell trade to modern IUU fishing networks

What began as research into historical data on rare hawksbill sea turtles could help illuminate the shadowy modern world of illegal, unreported, and unregulated fishing, according to a new paper published in the journal Science Advances. The study also revealed that a dramatically larger number of the critically endangered turtles were killed for the tortoiseshell trade, six times higher than earlier estimates.

The project started nearly a decade ago when Dr. Kyle Van Houtan — then with the National Oceanic and Atmospheric Administration, now Monterey Bay Aquarium’s director of science and senior author of the paper — was leading a sea turtle research program in Hawaii.

“Our goal was to give hawksbills the attention they deserve,” Kyle says. “Hawksbill sea turtles are critically endangered throughout their range, mostly due to threats from illegal harvesting.” The turtles can grow to more than three feet long and 150 pounds and are distinct for their beautiful, mottled shells. 

“They also have a long slender neck that allows them to search for food in the cavities between branches of coral in a reef. There they find sponges, algae and other invertebrates,” Kyle explains.

“They can really shape a coral reef, allowing coral colonies and the reef ecosystem to thrive,” says Dr. Emily Miller, assistant research scientist at the Aquarium and the paper’s first author. Read more…

Diving into sea otter recovery in Alaska’s Glacier Bay

Glacier Bay National Park in Alaska is home to more than twice as many northern sea otters (Enhydra lutris kenyoni) as all of California is to southern sea otters (Enhydra lutris nereis). Studying the thriving northern species may hold important clues for the future of the recovering southern species. In August, Monterey Bay Aquarium researcher Jessica Fujii spent two weeks studying the Glacier Bay population in the wild.

When she’s not studying sea otters in Alaska during the summer, Jessica Fujii observes otter behavior around Monterey Bay. Photo by Michelle Staedler

Jess is a senior research biologist with the Aquarium’s Sea Otter Program. She studies both wild sea otters and pups raised by surrogate otters so they can be returned to the wild—as was the case with two juvenile males earlier this month.

“Mostly I’m looking at sea otter behavior and foraging ecology—what they’re eating and what that may tell us about the rest of the ecosystem,” Jess says. “It involves a lot of going out in the field and watching the otters from shore.”

This summer, she worked aboard the Alaskan Gyre, a 50-foot U.S. Geological Survey vessel.

“It looks like a fishing boat, but it’s been converted for research purposes,” she says. “What used to be the fish hold is now sleeping quarters and storage.” With six or seven others aboard, “it was cozy; there’s not a lot of extra space.”

The converted fishing boat Alaska Gyre was home base for scientists working in Glacier Bay.

The trip was part of a longstanding collaboration between the Aquarium and researchers with the USGS Alaska Science Center. The two groups sometimes share insights and help each other observe or capture sea otters: “Having that crossover can be really helpful,” Jess says. “It’s also a way to make sure we’re maintaining comparable methods.”

Read more…

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