The Pacific angel sharks, also known as Squatina californica, are ambush predators with wing-shaped pectoral fins, flattened bodies and gray, brown and black coloring. Their births follow the natural pupping patterns for most sharks, which is typically March through June, said director of husbandry Christina Slager.
"We are very excited because it's a very rare occurrence," Slager said. "We're looking forward to being able to learn things about the pups."
The pups are being monitored hourly from behind-the-scenes nursery tanks. They weighed between 115 to 120 grams at birth with a length between 21 and 24 centimeters.
The four pups will be available for the public to view in about two years when they are expected to reach adulthood, Slager said.
The aquarium launched a research project in 2008 to explore the breeding patterns and migration in conjunction with tidal cycle, current flows and oceanographic data of angel sharks and also sevengill sharks, considered to be the largest predators in the San Francisco Bay.