Events & Media

November 29, 2016

Varied Responses to Marine Protected Areas
Bren researchers find that different users redistribute differently after MPAs are established

Since the early 1900s, California has established marine protected areas (MPAs) to conserve biodiversity in its coastal waters. Initially, those areas were established haphazardly with little regard for regional conservation goals, and were not managed under a coherent plan. That changed with the passage of the Marine Life Protection Act in 1999. The Act created a state-wide network of new and existing MPAs and required a cohesive, regularly updated plan to manage them.

Aerial photographs like this were used to monitor dispersal of activity after marine protected areas were established in the Channel Islands.
Photograph courtesy of Channel Islands National Marine Sanctuary

MPAs alter the location and pattern of fishing and non-fishing activities. But what does the shift by marine users look like? Are all responses to MPAs by all users always the same?

Scientists and managers tend to oversimplify the effects of such redistribution of activity by assuming that all users do indeed respond in the same way, or by omitting stakeholder activity from the decision-making process once protected areas have been established. For example, scientists and managers may assume that all fishers refocus their efforts by moving just outside the boundaries of MPAs to capitalize on the productivity of the new protected area. This implies that fishers of fast-moving and spatially dispersed species, such as squid, would respond in the same way as those harvesting more sedentary species, like sea urchins. But user groups might actually redistribute their activities in different ways, which should be considered in future network planning and management.

The authors of a recent paper, Bren School postdoctoral researcher Reniel Cabral, Dean Steve Gaines and their co-authors examined the actual redistribution of activities after MPAs were established. In “Drivers of redistribution of fishing and non-fishing effort after the implementation of a marine protected area network,” published in the October issue of Ecological Applications, the authors determine, based on a case study of the California Channel Islands MPA network, that that the redistribution effects of MPAs vary by type of marine activity. (Read full article)

The authors took an innovative approach to analyzing redistribution of fishing and non-fishing activities, using long-term aerial surveys of boats around the California Channel Islands. The surveys document user type and location during six years before and eight years after the MPA network was established.

The authors find that commercial and recreational users, such as divers, urchin harvesters, and commercial fishers, respond differently to MPAs depending on what activity they are conducting and the biology of the species they are targeting. For example, dive boats prefer to visit areas near MPA borders, as their passengers may dive within the MPA and also fish recreationally outside the border. On the other hand, urchin harvesters are not attracted to MPA borders, because urchins do not move a lot and are therefore less likely to cross MPA borders. The MPA benefit for urchins would likely come in the form of increased larval exportation from inside MPAs to fished areas beyond them. Accordingly, the authors maintain that the effects of MPAs on the health of fisheries, fish populations, and ecosystems would be better understood if the analysis included such differences in redistribution for multiple activities.

State regulations require that California’s MPAs undergo regional comprehensive reviews every five years. The reviews present a significant opportunity to incorporate the authors’ findings. Including redistribution information in the reviews would result in a more accurate description of MPA impact. Improving accuracy is desirable because the reviews will influence policy and public sentiment regarding the future of California’s MPA network.