Hundreds of jellyfish wash up on Morro Bay beach: good for turtles, bad for swimmers

The jellyfish are likely moon jellies, a common jellyfish species that is known to breed in great numbers, said Steve Johnston, a staff member at the Monterey Bay Aquarium. Occasionally, a couple of things conspire, he said, and the conditions are just right for a population explosion. The factors that control jellyfish population are algal blooms -- which the jellies feed upon -- water temperature and currents. Jellies float at the mercy of winds and current and, inevitably, some of them drift close to the shore and get caught in the surf where they wash ashore and die, Johnston said. On the beach, the jellies look like translucent, gelatinous blobs. People who spend a lot of time on the water report seeing large schools of the animals floating offshore. ‘The concentrations of them in some spots are pretty amazing,’ said Mike Harris, a marine biologist with the state Department of Fish and Game in Morro Bay. Harris said he’s also seen more leatherback sea turtles in the area. Leatherbacks feed on jellyfish.