Marine Protected Area Design

PISCO scientists have been engaged as scientific advisors to California’s Marine Life Protection Act (MLPA) Initiative since 2004. In this capacity, PISCO science has informed the “rules of thumb” for design of effective MPA networks and helped to answer a variety of scientific questions that have arisen in the process of MPA design.

Rules of thumb for MPA network design

An analysis of species assemblages in the kelp forest and rocky intertidal delineated 5 statistically distinct bioregions within the southern California bight.
Credit: Pete Raimondi and Emily Saarman

MPAs should encompass a variety of marine habitats across a range of depths and environmental gradients

PISCO’s monitoring programs have helped to elucidate how ecosystems and the communities they support vary across space and time. This information has been used to define biologically distinct regions within California and to identify the scales across which habitats should be replicated within MPAs for effective protection of the full diversity of marine communities in California.

Median max movement of 25 west coast fish species from PISCO graduate student Jan Freiwald's review and analysis of fish movement literature.
Credit: Jan Freiwald, Larry Allen, and Emily Saarman

MPAs should be large enough that adults don’t move out of them too frequently and become vulnerable to fishing

The movement range of fish and invertebrate species has implications for MPA size guidelines. By understanding the mobility of a wide range of species, scientists can predict which species will likely be protected by an MPA of a given size. A review and analysis of the fish movement literature conducted by PISCO graduate student Jan Freiwald evaluated movement information for 25 west coast temperate reef fishes. This work informed the MPA size guidelines used in the MLPA process.

Analysis of dispersal distance for algae, invertebrates, and fishes based on pelagic larval duration from Kinlan and Gaines (2003).
Credit: Brian Kinlan and Steve Gaines

MPAs should be close enough together that sufficient larvae can disperse from one to the next

PISCO’s genetic and recruitment studies have helped to define larval dispersal distances. PISCO scientists applied genetic models and a synthesis of the literature on population genetics of marine species to generate estimates of larval dispersal distances for algae, invertebrates, and fishes. These dispersal distances were used to generate guidelines for spacing adjacent MPAs.

Additional scientific questions for MPA design

Conceptual model for determining the level of protection conferred upon an ecosystem within an MPA that allows specific extractive activities.
Credit: Mark Carr and Emily Saarman

How well will an ecosystem be protected if a specific fishing activity is allowed within an MPA?

Applying their extensive knowledge of California’s coastal marine ecosystems, PISCO scientists and coordinators helped to develop a conceptual model to classify the potential impacts of extractive activities on marine communities. The conceptual model considers both direct impacts (e.g. habitat destruction) and indirect impacts (e.g. community alteration due to removal of a top predator) through a series of questions in a decision tree. The answers to these questions, derived from diverse sources including published life-history and species movement information, catch records, gear-type information, and discussion with scientists and fishers, lead to an assigned “level of protection” for each use proposed within an MPA.

Species-area relationships drawn from a variety of biological surveys were used to determine the amount of habitat needed to encompass 90% of the habitat-associated biodiversity.
Credit: Pete Raimondi and Emily Saarman

How much habitat is needed to protect the biological community associated with that habitat?

PISCO scientists used a variety of information sources, including PISCO kelp forest and rocky shore monitoring data to assess the relationship between habitat size and biodiversity for a variety habitats. Using this relationship, the MLPA Science Advisory Team was able to set thresholds for the amount of each habitat needed to encompass 90% of the associated biodiversity. This information helped to inform habitat replication and spacing analysis for MPA network design evaluations.

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