A paper published by MARINe shows that resources can be fully protected in highly visited tidepools if public access is limited and oversight is provided to reduce collection.

Owl limpets are monitored by MARINe because they are ecologically important, long-lived (life-span of 15 years or more), and are collected by humans for bait or food. Their large size and conspicuousness in the upper intertidal made them vulnerable to poachers who can collect thousands of individuals in a single visit.

These large limpets are also vulnerable to collection in “protected areas” by the uninformed public, who cumulatively, may take a significant number of these protected animals over time. Often, poachers and others selectively pull the largest sized of these animals off the rocks. What many people don’t understand is that these limpets change their gender from male to female as they grow larger. Unfortunately, collecting the largest animals of this species significantly reduces the number of reproductive females, thus affecting the overall population.

Sagarin‘s analysis in Marine Biology¹ showed that high level of protection from poaching and collection is the most important management tool for successfully maintaining healthy owl limpet populations. This is not the same thing as protecting the area from visitation. The monitoring data at Cabrillo was instrumental in distinguishing between the two. Cabrillo National Monument is visited by nearly 100,000 people each year. Given that the tidepools cover a relatively small portion of land (approximately 128 acres, of which only 40 acres are easily accessible) concentrating the usage, this translates to a very high visitation rate at the tidepools.

Cabrillo park rangers, however, do several things to limit overuse by the public while allowing high visitation. First, access to the park is controlled by the US Navy, and access is restricted to daytime hours and only when Park rangers are present. Second, monument Rangers patrol the area regularly. Third, rangers and dedicated volunteers interact directly with the public during low tide, educating them about the resources and providing critical oversight to deter collection activities. Rangers have ultimate enforcement authority and can fine visitors if they determine a visitor is harming resources at the park.

In the study by Sagarin, it was found that the number of visitors to a site does not affect limpet size. Limpet sizes at Cabrillo were compared to limpet sizes at many other MARINe sites across Southern California. Limpet size is found to be comparatively large at Cabrillo and similar to other locations along the coast, many of which are completely inaccessible to the public. These large sizes in limpets support the premise that limpets are being protected effectively from poaching and collecting. Only in those places where no enforcement exists, unfortunately a substantial portion of the coast, did owl limpets show negative signs of human impact.