Aerial surveys and distribution models enable monitoring of fishing in Marine Protected Areas

Marine Protected Areas are rapidly becoming a central method for conservation of aquatic resources, but quantifying the success of these reserves in restricting fishing remains a challenge. Monitoring fishing has long been difficult - there are many types of fishers accessing resources in remote places from a diverse set of platforms (e.g., boat types). We used aerial surveys in conjunction with a novel application of species distribution modeling to develop a method for monitoring the change in fisher distributions following the implementation of MPAs. Aerial survey transects were conducted for 3.5 years before and after the implementation of 25 MPAs along the mainland southern California coast in 2012 and resulted in 13,558 vessel observations representing 19 different boat types. We compared actively fishing commercial and recreational vessels with non-fishing vessels to evaluate the use of MPA areas. There was a statistically significant decrease in proportion of vessels observed within MPAs from 17.5% before to 11.4% after MPA implementation, with MPA-implementation, fishing type, and the interaction all predicting the probability of a vessel being observed within MPA boundaries. Distribution models showed both an overall shift in distributions across all boat types and a decrease in predicted probability of habitat suitability of fishing within MPA boundaries after MPA implementation, although results differed among boat types. We illustrate the utility of distribution modeling for evaluating spatial patterns in human activities, providing a powerful tool for conservation biologists and demonstrate the importance of monitoring programs for establishing both baseline and response data needed for adaptive management of marine ecosystems.