California Marine Life Protection Act

The Marine Life Protection Act, signed into law by the California State Legislature in 1999, directs the State of California to evaluate and/or redesign existing state marine protected areas (MPAs) and create a new network of MPAs to protect California’s marine ecosystems. Marine scientists serving on the Science Advisory Team to the Marine Life Protection Act Initiative provided guidelines for the design of MPAs to meet the goals of the Act. Stakeholders use the scientific guidelines to develop proposed plans for the number, size and locations of MPAs.

MLPA Intiative

The California Marine Life Protection Act Master Plan for Marine Protected Areas describes scientific guidelines for design of a MPA network. The Science Advisory Team determined that no single optimum configuration of MPAs in a network protects the diversity of species and habitats and the diversity of human uses of marine environments. Depending on ecosystem characteristics and types of human uses, a range of different network designs may meet goals of the Marine Life Protection Act in California state waters.

How PISCO Informs the MLPA Network Design

PISCO has played key roles on the Science Advisory Team to California’s MLPA Initiative, helping to generate guidelines for the distribution, size and spacing of MPA networks in the southern, central, and northern study regions of the MLPA. For example, PISCO data generated by the large scale, long-term ecological and oceanographic monitoring programs have been used to:

  • Define geographic patterns of ecosystem variation (termed “bioregions”).
  • Species diversity-habitat area relationships also generated by the monitoring program were used to determine minimum habitats areas for ecosystem protection.
  • Refine a 1-km resolution Regional Ocean Model System (ROMS) model to estimate larval connectivity among MPAs in proposed networks.
  • Describe patterns of species distributions used to refine the ROMS-based model.

Using these data PISCO has used its interdisciplinary nature to develop these syntheses:

  • Combining oceanography and ecology PISCO monitored temperate reef fish movement, these results formed the basis for MPA size guidelines.
  • Using genetic-based estimates of larval dispersal distances PISCO informed spacing guidelines of the networks of MLPA marine protected areas.


The Science Advisory Team developed the following guidelines for MPA design to meet the goals of the Marine Life Protection Act.

  • Every “key” marine habitat should be represented in the MPA network. Key habitats are rocky shores, sandy beaches, coastal marsh, tidal flats, estuarine waters, surfgrass, eelgrass, kelp, rocky reef, soft bottom, submarine canyons, pinnacles, upwelling centers and retention areas.

  • MPAs should extend from the intertidal zone to deep waters offshore.

  • The minimum area of a MPA is 9-18 square miles; the preferred size is 18-36 square miles. The alongshore span of a MPA should be a minimum of approximately 3-6 miles, preferably 6-12.5 miles. The offshore span should extend from the intertidal zone to deep waters.

  • MPAs should be placed no further than 31-62 miles from each other to facilitate dispersal and connectedness among MPAs in a network. Due to their complex ocean circulation and geology, the guideline for MPA spacing does not apply to the Channel Islands.

  • "Key" marine habitats should be replicated in multiple MPAs across large environmental and geographic gradients.

  • At least three to five replicate MPAs should be designed for each habitat type within a biogeographic region. The two biogeographic regions defined for the state of California include the regions from (1) the Oregon – California border south to Point Conception and (2) Point Conception south to the U.S. – Mexico border.

  • For the South Coast Study Region from Point Conception to the U.S. – Mexico border, five bioregions were defined by their unique ecological and physical characteristics: (1) north mainland from Point Conception to Marina Del Rey, (2) south mainland from Marina del Rey to the U.S. – Mexico border, (3) west Channel Islands, including San Miguel, Santa Rosa and San Nicolas islands, (4) mid Channel Islands, including Santa Cruz, Anacapa and Santa Barbara islands, and (5) east Channel Islands, including San Clemente and Santa Catalina islands. At least one replicate MPA should be designed for each habitat type within a bioregion.

  • Placement of MPAs should take into account local resource use and stakeholder activities.

  • Placement of MPAs should take into account the adjacent terrestrial environment and associated human activities.

  • The design of a MPA network should account for the need to evaluate and monitor biological changes within MPAs.

More information about guidelines for design of MPA networks can be found in Section 3 of the California Marine Life Protection Act Master Plan for Marine Protected Areas

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