It is June 21. Do you know what that means?

It’s time to wish a very happy birthday to Zoe and Sierra!

Zoe and Sierra have been together since they were born. Health issues with their mothers left these two newborn pups unable to survive in the wild.

They joined the New England Aquarium family in 2011.

Zoe and Sierra in 2011, shortly after arriving here ...
and in 2019.


Zoe the California sea lion


Zoe and Sierra have been together since the day they were born. You can often find them together – snuggling, playing, or exploring. If you see one of them, you are bound to see the other nearby.

Exploring behind the scenes, sharing toys, and playing “keep away,” or even just sharing an afternoon nap, these two honorary siblings are never far apart.

As babies, they often curled up in this little sandbox. It is still a favorite sleep spot!

Since sea lions are native to the West Coast, you may be asking…

How did Zoe and Sierra end up at the New England Aquarium?

The Santa Barbara Marine Mammal Stranding Center in California tended to two pregnant sea lions on the beach, who appeared to be in distress. The sea lions were experiencing seizures, indicative of domoic acid poisoning, and were not able to take care of the pups, nor were they interested in doing so. The stranding center’s only option was to feed a special formula, high in fat and ground-up fish, to Zoe and Sierra – while looking for a home for them. We had the space and staff to care for two sea lions in our Marine Mammal Center, so we offered to provide the care that they needed.

What is Domoic Acid?

Increasing water temperatures combined with excess phosphorus from runoff create harmful algae blooms, known as red tides, in the ocean. Under these circumstances, the algae produces large quantities of diatoms. These diatoms then release the neurotoxin domoic acid.

Everything in the ocean is connected

That’s why marine mammals are susceptible to domoic acid poisoning.

ocean food web

Filter feeders eat the algae, inevitably taking in domoic acid. Larger fish eat the filter feeders, and sea lions eat the larger fish. The domoic acid affects the hippocampus in the brain of sea lions and causes lethargy, tremors, seizures, and even fatality. It is similar to how shellfish poisoning affects people.

Conservation Context: What Can You Do to Help?

Ride your bike, walk, or take public transit instead of your car whenever possible. Encourage your family and friends to do the same. By reducing the use of fossil fuels, you can help slow down the rate of global warming.
Another simple solution? Use phosphorus-free laundry detergent and fertilizer! This will reduce the amount of phosphorus that reaches the ocean and feeds the red tide.