The Rocky Intertidal Zone

Download the "Life In the Intertidal Zone" brochure

Enjoying Tidepools
Knobby Seastar

Knobby seastars are fascinating residents of the tidepools at Cabrillo National Monument.

NPS Photo


Possible Temporary Closure of Road to Tidepools - On weekends and Holidays and when there is a good low tide the road to the tidepools may be closed periodically when tidepool parking lots are full to capacity. The road to the tidepool area will be closed (usually 30-45 minutes), until sufficient capacity in the parking areas becomes available. This temporary closure of the road allows for traffic to flow freely and allows a more pleasant experience for the visitor by reducing the number of people and reducing the damage to the fragile ecosystem. Please plan your trips to allow for this delay. Thanks for your patience with our staff when dealing with this issue.


Windows to the Sea

On the western side of Point Loma lies the rocky intertidal zone, a window into the ocean ecosystem that lies along of San Diego's coast. During periods of low tide, pools form along this shore in rocky depressions. In them you may see flowery anemones, elusive octopi, spongy deadman's fingers, and a myriad of other creatures. The tidepools are a wonderful discovery zone, but be careful if you visit.

The intertidal area is a very sensitive ecosystem. Few animals in this ecosystem can harm humans, but many animals are sensitive, and can even be killed, when handled or just touched by humans. Ask a ranger or volunteer how you can best explore the tidepools without harming them.

Ranger walks are available during most low tides and a slide program is shown daily at the park visitor center. Low tides during convenient daylight hours are most common in the winter during full and new moons. Check a tide chart or give us a call at (619) 557-5450, extension 0, before you visit for the best time to explore the tidepools.

Inhabiting the subtidal zone, outside of Cabrillo National Monument’s boundaries, is the kelp forest. This is a habitat where large marine plants (kelp) form tall “trees” making an underwater forest. The kelp helps support life in the deeper ocean. These plants are fed upon by sea urchins and abalone. Large fish and mammals also inhabit the kelp forest, eating the sea urchins and abalone.

The Cautious Visitor

Please keep in mind that algae-covered rocks are wet and slippery. Because you can expect to get wet, wear shoes with good traction and wear clothes you don't mind getting wet. You will be more relaxed, have more fun, and be safer if you don't have to worry about your good shoes or pants getting doused by a stray wave.

The Plight of the Owl Limpet

The tidepools at Cabrillo National Monument are currently being studied to assess the impact human visitors have on them. Initial results seem to indicate that humans are contributing substantially to the decline of many species. The National Park Service, however, believes that we are capable of resolving the problems that face the intertidal animal and plant life so that we may – hopefully - undo some of the damage and help these species survive.

For example, consider the plight of the owl limpet...

Owl limpets are still fairly common on the rocks of Cabrillo's tidepools. But so too were abalone at one time. Then people discovered how good abalone tastes and they began disappearing. Now it is nearly impossible to find even a small abalone at Cabrillo. Like the abalone before them, owl limpets today may be in danger of disappearing simply because they taste good.

In the 1970s, owl limpets that lived in Cabrillo's tidepools were abundant and averaged 50.25mm across in size. Meanwhile, only four miles up the coast at Sunset Cliffs, owl limpets at that time averaged only 30.61mm. The older, larger owl limpets at Sunset Cliffs were apparently being gathered for human consumption. At Cabrillo National Monument, however, no collecting of any kind is allowed, so the animals are able to grow older and bigger.

Here is a curious and worrisome twist: owl limpets are hermaphroditic - in other words, they are both male and female during their life span. They are male when they are young (and small), and female when they get older (and larger). This is important because it may be that owl limpets are not growing large enough to fulfill the female role of reproduction at Sunset Cliffs. At Cabrillo, however, the tidepools are closely monitored and owl limpets are able to grow to a large, female, size.

It is possible that protected areas like Cabrillo’s tidepools serve an important function as breeding grounds for owl limpets and other commercially important species in the area. Most limpets hatch from eggs into a larval form that drifts with the ocean's currents to their eventual homes. Perhaps many owl limpets that spawn (hatch) at Cabrillo are swimming away and replenishing other areas of the coastline with young owl limpets. If this speculation is the case, then it is very important that we protect and preserve areas like the Cabrillo tidepools.

A recent study, however, suggests that even the Cabrillo owl limpet population is in danger. Between 1990 and 1995, owl limpet numbers declined an overall 23%, and individual animals were found to average only 45mm in length (5.25mm less than they were twenty years ago). Park Rangers sometimes discover people collecting illegally in the park, and are worried that this poaching may be causing the decline. The park has increased the presence of Park Rangers and Volunteers in the tidepools, and Rangers take a strong stance on enforcing the "No Collecting" policies in the park.

We hope you will visit and discover the Cabrillo tidepools. If you do, please remember to be careful and be mindful of the rules, so that we may preserve the diversity of life that exists here.

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