Sanctuary Integrated Monitoring Network
National Marine Sanctuaries

Rocky Shores

Rocky Shores_ map
Figure 1. Zones of rocky shores within the Monterey Bay, Gulf of the Farallones, and Cordell Bank National Marine Sanctuaries. [View Larger]
In Gulf of the Farallones and Monterey Bay National Marine Sanctuaries, the rocky shores are characterized by a fascinating and diverse array of intertidal organisms. The dramatic influence of the tidal cycle exposes this region's inhabitants to large fluctuations in temperature, desiccation (drying out) and wave action twice per day.


Rocky shores are divided into a series of zones that are defined by the amount of time the rocks are exposed to air and water. Individual species tend to occupy different parts of the intertidal gradient from the high intertidal zone, where environmental stress is highest, to the low intertidal zone, where biological interactions prevail.

The Splash Zone: Few organisms survive here. Those that can (e.g., barnacles, limpets and a type of green algae) are almost always exposed to the air and are rarely submerged by water.

The High Zone: Organisms that inhabit this zone are exposed to air more than 70 percent of the time and must develop adaptations to survive the long dry periods. For example, limpets, chitons and black turban snails form a watertight seal onto the rocks with their shells to protect themselves from drying out.

The Mid Zone: This zone is densely populated. California mussels often form large beds that provide important refuge and habitat for a variety of other invertebrates and algae.

The Low Zone: In this zone, organisms may be exposed to air just a few times a month so they are more resilient to waves and less resilient to air exposure. Inhabitants include the giant green anemone, the purple sea urchin, the sunflower star and the beautiful sea palm.

Conservation and Management Issues

Crevices and underhangs are home to black abalone Haliotis cracherodii and black turban snails Chlorostoma funebralis. Black abalone were declared an endangered species in 2009.

The Striped shore crab (Pachygrapsus crassipes) is a small crab found on rocky and hard and mud shores of the west coast of North America.

There are a number of conservation concerns relative to this habitat. These include the following:


Monitoring programs are essential to understanding short- and long-term natural variability and for assessing the health of the region's rocky shores. Most current research and monitoring efforts have two main focus areas:
Staff from both the Gulf of the Farallones and Monterey Bay sanctuaries are involved in two rocky-shore research projects:

In the Monterey Bay sanctuary, a study on visitor use and marine reserves at Point Pinos in Pacific Grove has evaluated how visitors affect rocky-shore communities.

In the Gulf of the Farallones sanctuary, the Duxbury Reef Restoration Program analyzes visitor data, determines baseline species diversity patterns and abundance on the reef, and identifies high- and low-impact areas regarding visitor use.