Scale Dependent Drivers of MPA Performance: A Case Study of the Spiny Lobster (Panulirus interruptus) on Santa Catalina Island

Marine Protected Areas (MPA) have become a key tool for resource managers in the conservation and management of coastal resources. However, mismatches in the scale of MPA design and the scale at which target species utilize habitat may affect estimates of MPA performance. In this study we describe the utilization of intertidal habitat by the spiny lobster (Panulirus interruptus) inside and outside of a long standing MPA on Santa Catalina Island. Our results indicate that lobster populations outside the MPA were greater in number and had a higher ratio of reproductively active females. This difference is suggested to be due to the presence of mussel beds outside of the MPA which comprised 75% of lobster’s diet as estimated through stable isotope analysis. However, such habitat is often not incorporated into and, can fall below scales at which MPAs that target lobsters are designed. Through the application of landscape based survey methods, GIS modeling, spatial statistics, and stable isotope analysis, we highlight how the performance of an individual MPA may originate at sub-meter scales via strong interactions between the underlying geological and biogenic habitat; interactions which are not always incorporated into the design of individual MPAs. More specifically, strong differences in the underlying geology of our sites may in part drive differences in the prey communities available to foraging lobsters. Thus, the underlying geology may in part drive MPA performance at Santa Catalina Island. We close with a discussion on the need to integrate landscape based survey approaches, assessments of sub-meter geological and biogenic habitat with, stable isotope analysis to move towards incorporating bio-energetic performance of MPAs into current assessments of MPA success.