Since August 2020 there have been several instances where large numbers of Pismo clams have become unburied during low tide events. These events appear to be localized and have occurred in several locations along Pismo State Beach.
The cause of these events remains unclear. Several possibilities include harmful algal blooms that produce domoic acid, bacterial and fungal infections that degrade muscle and visceral tissue, stress from environmental changes such as temperature fluctuations, and overcrowding. In the last five years, the Pismo clam population has increased, and some unburying events are in these densely populated areas.
The Department of Fish and Wildlife is working collaboratively with State Parks, California Department of Public Health, and researchers at California Polytechnic State University in San Luis Obispo to investigate possible causes.