Publication Date

Spring 2015

Degree Type


Degree Name

Master of Science (MS)


Environmental Studies


Lynne Trulio


Body size, California, Gastropods, Intertidal, Marine protected areas, Owl limpet

Subject Areas

Environmental studies; Environmental science; Ecology


As the human population has exponentially increased, so have anthropogenic effects on the ocean including pollution, eutrophication, acidification, changes in sea level, and overfishing. The California coast is visited by millions of people every year and is subject to a range of impacts. In the near-shore marine environment, people collect intertidal gastropods for food, bait or recreation. Collecting these animals has caused a decline in body size because humans preferentially take the largest individuals. Marine protected areas (MPAs), established to protect marine resources, may serve to reduce impacts to species, including gastropods. I collected 2510 individual samples to determine the body size and frequency of five gastropod species along the central California coast to assess whether MPAs may protect intertidal species from over-exploitation. I hypothesized that gastropods in MPAs, compared to non-MPAs zones, would have larger body sizes and be more frequent and be similar in size to museum specimens. I found that, for two of the five species studied, gastropods were larger inside MPA field locations; for most species the average size of specimens from MPA sites was significantly larger than museum specimens and collected gastropods had higher frequencies of presence inside MPAs. For coastal managers, these results indicate that MPAs are effective for some gastropod species studied, but in order for all species to benefit fully from MPA protection continued research is necessary to determine species-specific requirements.