The U.S. Fish and Wildlife Service on Friday said the shootings happened last September around Asilomar State Beach in Pacific Grove.
The otters are protected under the Endangered Species Act and Marine Mammal Protection Act, which could lead to $100,000 fines and jail time for anyone found guilty of the shootings.
Two of the otters were shot in the head, the third through the back.
Anyone with information is asked to contact the service.