The facility's outdoor exhibits had already been open to the public.
Asked if there was any truth to speculation that perhaps the aquarium's marine wildlife had been affected by the monthslong shutdown, Nicole Meek, director of visitor operations, said it was "hard to say."
"But the truth is that our animals continue to get the regular care and engagement that they always got," Meek said. "So that some of them might notice that there weren't as many people on the outside of the glass, but some of them might have not."
Meek noted that the animals were not isolated "from those in their families or those in their enclosures, so they really didn't experience what we experienced - being quarantined or working from home, home schooling, etc."
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The Aquarium of the Pacific's indoor exhibits reopened at 25% capacity, in accordance with health guidelines. Face coverings are required along with physical distancing, and extra hand-sanitizing stations have been installed.
Meek encouraged visitors to make reservations in advance.
"Don't come down here and be turned away or be disappointed because there's a wait," she said, urging the public to visit the aquarium's website to purchase tickets in advance.