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Severe Entanglements Threaten Recovery of Guadalupe Fur Seal Population

The Marine Mammal Center has found that impacts from entanglement in ocean trash and fishing gear is damaging the chance of recovery for species like the threatened Guadalupe fur seal, leaving our experts deeply concerned.


August 14, 2020

Since the beginning of June, The Marine Mammal Center has admitted eight Guadalupe fur seal and California sea lion patients suffering from life-threatening entanglements. If left untreated, this condition can prevent the animal from finding enough food, cause deep wounds and can even result in an early death.

What is especially concerning to our veterinarians is not necessarily the number of animals coming in wrapped in ocean trash and fishing gear, but rather the severity of these entanglements. Experts are deeply troubled by the fact that these life-threatening entrapments are harming the long-term recovery of endangered and threatened species, like the Guadalupe fur seal.

“Trash and plastic pollution in our ocean impacts seal and sea lion patients we rescue each year, as well as large cetaceans such as whales,” says Dr. Cara Field, our Medical Director. “It’s especially alarming to see these preventable entanglements in Guadalupe fur seals because this species is still recovering from the brink of extinction.”

Snaggle pre-admit
Our experts are concerned that the threatened Guadalupe fur seal species is at risk of not recovering from the brink of extinction due to impacts from entanglements. Photo by Cara Field / NOAA permit #18786


In fact, Guadalupe fur seals have the highest prevalence of entanglement in ocean trash and fishing gear out of any marine mammal we rescue. Two major entanglement studies co-published by Daniela Bárcenas de la Cruz, an alumni of our Teaching Hospital, found that approximately 25 percent of Guadalupe fur seals admitted into our care from 2001-2015 were suffering from the effects of ocean trash entanglements.

Overall, not much is known about Guadalupe fur seals because they spend most of their life far offshore. This makes researching this elusive species more difficult, which is a key reason why we work closely with partners in Mexico to investigate the life history of these animals.

Researchers like Tenaya Norris, one of our scientists, are collecting valuable data from Guadalupe fur seals at their main breeding site in Mexico to investigate where they travel in the ocean, how much time they spend on land and how many are in the population each year.

GFS tagging
Center scientist Tenaya Norris (right) adds a satellite tag to a Guadalupe fur seal patient to track its movements in the wild after release. Photo taken pre-COVID-19 / Photo by Bill Hunnewell / NOAA permit #18786


This crucial data teaches us how to better protect this threatened species from entanglements and other significant threats that diminish the animals’ survival rates, like impacts from overfishing and warming ocean temperatures due to climate change.

In conjunction with collecting this important data, our experts work to solve the issue of ocean trash and plastic entanglements. This is critical because while entanglements affect animals of all ages, our research shows younger animals, like our recent Guadalupe fur seal pup patients Neshema and Dansam, appear to be more susceptible than adults.

Not only are pups still mastering the art of fending for themselves in the wild, but an entanglement adds a whole new layer of challenges. You see, human sources of marine debris, such as packing straps or fishing gear, cause life-threatening entrapments around the heads, necks and bodies of marine mammals.

This heavy debris can prevent animals from swimming as well as they normally would, making hunting for fish more challenging than it already is for a young pup. This is likely partially why many animals that come to our hospital with an entanglement are often also suffering from malnutrition, which was the case for both Neshema and Dansam.

GFS Neshema
Guadalupe fur seal pup Neshema rests on the pool’s edge at our hospital while recovering from an entanglement and malnutrition. Photo by Bill Hunnewell / NOAA permit #18786


As one of only two facilities in California permitted to provide long-term rehabilitative care for this threatened species, the Center admitted these two Guadalupe fur seal pups after they were transported to our hospital by our partners at the Northcoast Marine Mammal Center. After six weeks of receiving life-saving care, Neshema and Dansam were released back to the wild with second chance at life.

But for those young animals that don’t make it to our hospital for care, their entanglement inevitably gets tighter and tighter as they grow from a pup into adulthood, likely to cause an early death.

Seals and sea lions are intelligent and curious, which unfortunately means they can see trash as something to eat, investigate or play with—not knowing that this new object could end up being fatal. As the rate of ocean trash and fishing gear continues to rise, the need for a worldwide network of entanglement response professionals is greater than ever before.

Monofilament in Mexico
Center staff member Sophie Guarasci holds up a monofilament fishing line that was removed from a sea lion during a disentanglement in Mexico. Photo taken pre-COVID-19 / Photo by Sarah van Schagen


Thanks to our more than 45 years of experience on the front lines of marine mammal rescue and rehabilitation, our experts are able to support and train organizations and individuals in effective rescue and entanglement response techniques.

“We want to not only share our entanglement response expertise widely to support the recovery and treatment of entangled marine mammals worldwide but also identify and reduce these occurrences,” says Dr. Field. “Ocean trash knows no international boundaries so it’s critical as the world’s largest marine mammal hospital that we help support and build the network of response organizations dedicated to tackling the issue of ocean trash and the conservation of these important species.”

You Can Be a Marine Mammal Hero

As you can imagine, ocean trash is a persistent threat to all marine mammals. None of this life-saving work would be possible without your support.

You can help provide the critical care entangled patients like Neshema and Dansam need, as well as support efforts to prevent entanglements from happening in the first place.

Your special gift will help our experts to:

  • Use innovative rescue tools to capture wild, entangled animals using advanced sedation, tracking and rescue techniques.
  • Perform complicated surgeries to repair injuries caused by entanglements.
  • Train veterinarians and animal experts from countries developing rehabilitation and conservation programs so they can rescue and treat entangled animals on their own coastlines.

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