The Department updates the message as needed. Callers may leave a message at this number to request more detailed information. During late spring, summer, or fall, localized patches or streamers of color appear in the ocean or bays along the California coast. The color of the water comes from the millions of tiny organisms in the water. Water color varies from brown to red depending on how many and what kinds of organisms are present.
Many people believe that red tides cause shellfish to be toxic.
Most red tides are harmless . Toxin-producing organisms do not generally cause red tides. Although the presence of a red tide is a warning that shellfish may be toxic, the absence of a red tide does not mean they are safe to eat . Shellfish can consume enough toxic organisms to become toxic even when there is no visible red tide. Toxic mussels are very dangerous because people eat the entire mussel including the viscera.