3 months ago, a sick Otto the sea otter was rescued in Morro Bay. On Friday, he came home

A Morro Bay sea otter who spent three months rehabilitating in Marin County from domoic acid poisoning was released back into the harbor Friday morning to the delight of a crowd who came to see him off.

Surrounded by an enthralled group of about 40 bystanders who snapped photos and videos, Otto the otter slowly waddled out of his cage about 9 a.m., took a look around him, and then plunged into the bay north of the Morro Bay Natural History Museum.

“This is the first time that we’ve found an otter that was still alive after becoming sick with domoic acid,” said Shawn Johnson, the mammal center’s director of veterinary science. “For the next week, we’ll be monitoring his movements. We’ll see how well he grooms and forages and relates to other otters.”

Last May, the 9-year-old otter was discovered acting disoriented and lethargic near the South T-Pier in Morro Bay, even allowing boats to brush up against him.

The uncharacteristic behavior led to a call to the Marine Mammal Center, the nonprofit group that rescues and rehabilitates sick and injured marine mammals.

“We monitored him for about a week,” said Diana Kramer, the center’s operations manager. “He was underweight for his age, and he wasn’t gaining weight back over time. He had a severe wound on his nose from fighting with other otters. We realized he needed to be rescued.”

The otter, given the name Otto, was nursed back to health at the group’s veterinary hospital in Sausalito after being diagnosed with domoic acid toxicosis, a condition that attacks the brain and causes lethargy, disorientation and seizures. The toxin accumulates in shellfish such as crabs, clams and scallops, which sea otters eat in large quantities.

An MRI of Otto’s brain showed “a shrunken hippocampus,” the area of the brain known to play a role in memory and navigation, which tends to occur among animals with domoic acid toxicosis.

Otto has had tags surgically implanted in his stomach to allow researchers to track his movements and visually observe his behavior from the shore or by boat.

Produced by a type of algae called Pseudo-nitzschia australis, domoic acid has been known to attack other marine wildlife, including sea lions. The center has assessed the behaviors of sea lions diagnosed with the condition, but no neurological assessments of sea otters have been developed thus far.

Otto has now given scientists that opportunity.

“We’re going to learn about this condition and how brain lesions affect an otter’s ability to function,” Johnson said.

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