The Aquarium of Niagara announced Monday that its rescued California sea lion, Mia, has passed away.

Aquarium staff says Mia was humanely euthanized after a four-week period of declining health, including kidney failure.

Staff says Mia was rescued off the coast of California in June 2014 after being found stranded and suffering from pneumonia. The aquarium says Mia is believed to have suffered from domoic acid poisoning as a result of harmful algae blooms, which led to seizures during her rehab. Shortly after arriving at a care center in San Pedro, she gave birth to a pup, Isabel. Both Mia and Isabel were given a permanent home at the Aquarium of Niagara, where staff say Mia was able to receive the advanced level of care necessary for her survival over the past 9.5 years. 

"The Aquarium of Niagara has centered its identity on providing high-quality, long-term care for even the most vulnerable animals,” Chad Fifer, president and CEO of Aquarium of Niagara, said in a statement. “When you visit the Aquarium, you’ll encounter other non-releasable animals like Mia whose lives have been impacted by human activity – things like boat strikes, wildlife trafficking, and owner surrenders. These animals often require special accommodations and husbandry practices, and we are not only proud of our commitment to their wellbeing, but also our efforts to share their stories to drive conservation action for their counterparts in the wild.”

“As animal care professionals, we are extremely proud to have given the highest level of care to Mia for the past 9 ½ years,” Hallie Torre, associate curator, marine mammals and birds, said in a statement. “I have been working with Mia since the day she joined our Aquarium family, and I’ve watched her grow and develop alongside countless animal care specialists whose lives and careers have been shaped by their work with this incredible animal. Mia brought joy to many, and she will be greatly missed.”

The aquarium says that while her exact age was unknown, Mia was estimated to be at least 15 years old at the time of her death.