Large abalone are not threatened by the predators of their earlier life, but larger, and often more efficient predators now become important. Fishes, such as the cabezon, can dislodge some abalone and swallow them whole. Even very large abalone are no match for the crushing jaws of a bat ray. The sea otter is the most effective predator, capable of removing all exposed abalone within reach. Only those in deep crevices or under large rocks will survive.
Abalone are one of the first food items taken by otters as they move into new habitat.
Below are listed 6 major reasons for the decline. Commercial abalone harvesting is now primarily concentrated in southern California. Mortality of small abalone for many reasons. Abalone are easily over harvested because of slow growth and variable reproductive success. Initial high harvests cannot be sustained.