The barely 1-year-old sea lion, named Al Catraz by the center, was spotted on the dock on March 21 and arrived at the marine mammal center severely underweight.
Although it is not unheard of for a pup to be stranded at that location, it is a rare occurrence. Oswald said that about eight pups -- including animals thematically named "Fortress" and "Bird Man" -- have been rescued from Alcatraz over the past two decades.
When the male sea lion pup arrived at the center, Al Catraz weighed approximately 32 pounds -- half the ideal weight for a pup of that age, Oswald said.
"He was just really, really malnourished and in a bad location, so we immediately wanted to rescue him," Oswald said.
Initially too weak to eat on his own, Al Catraz received meals in liquid form for the first few days of his stay but has since begun gobbling about 4 pounds of herring a day without assistance.
How long Al Catraz will remain at the center will depend on whether being malnourished compromised his health, and Oswald said that veterinarians were monitoring the pup's condition.
"The focus right now is on getting him healthy," Oswald said. The pupping season, which runs through June, is the center's busy season, and Oswald said more than 60 elephant seals and at least 11 harbor seal pups were currently on site.
Oswald said it costs the center about a dollar per pound for the herring and that by the end of June the center will have fed about 40,000 pounds of herrings to animals in the center's care.
"Right now, we're pretty busy," he said.