Reducing human impacts on central Californian intertidal gastropods: are marine protected areas effective?

ABSTRACT

The central California coast is visited by millions of people every year, many of whom collect intertidal gastropods for food, bait or recreation in near-shore marine environments. The harvesting of these animals has caused a decline in body size because humans preferentially take the largest individuals. Marine protected areas (MPAs) may serve to protect gastropods from this impact. The average body size and frequency of four gastropod species from eight study locations along the central California coast were determined. Five study locations were in MPAs and three study locations were in non-MPA zones. Gastropods in four California museums were measured and compared to specimens collected in the field. Three of the four species studied were larger and/or more frequent in MPAs than outside MPAs, including both harvested species and one unharvested species. For three of the four species, the average size of individuals from MPA sites was significantly smaller than museum specimens, but this may be due, in part, to our sampling procedure. These findings indicate that MPAs can be effective at reducing human impacts for some species, but that further study is needed to make MPAs as effective as possible for more species.

KEYWORDS:

• Body size
• coastal management
• harvesting
• North America

Acknowledgements

We thank Rachel O’Malley, Department of Environmental Studies at San José State University and John Pearse at UC Santa Cruz for their sustained guidance on this project. We also thank Meagan Beaver for her help in the field and the graduate students in Environmental Studies for their help and advice. In addition, we thank the reviewers for their comments on the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Funding

This project was partially funded by a San José State University, College of Social Sciences research grant.