A major study assessing California’s Marine Protected Areas (MPAs) has confirmed that when properly designed and enforced, MPAs significantly increase fish populations, particularly among species targeted by fisheries. The findings, published in Conservation Biology, provide important insights as British Columbia is looking to implement its own network of MPAs, called the Great Bear Sea Marine Protected Area Network.
Researchers from the University of California, Santa Barbara (UCSB), have evaluated the effectiveness of California’s MPA network, which was established 25 years ago. Their analysis of 59 MPAs found that fish biomass (total weight of a fish population) increased across the network, with the biggest gains seen in areas with strict protections, diverse habitats, and a history of intense fishing pressure.
How California’s MPAs Were Designed
In 1999, California passed the Marine Life Protection Act (MLPA), requiring the state to restructure its marine reserves. Instead of creating a single large protected area, California implemented a network of 124 MPAs spread along the coast, allowing fish and other marine life to move between them. The goal was to support a wide range of marine life, protect key habitats, and support long-term fishery sustainability.
The approach is similar to what is being considered in British Columbia, where the federal government and Indigenous nations are working to establish an MPA network along the Pacific coast. The proposed Great Bear Sea MPA Network, covering 30% of the Great Bear Sea’s 100,000 square kilometres, is designed to balance ecological protection with sustainable use.
Of the 30% targeted for protection, more than half is already covered by existing MPAs. The Great Bear Sea MPA Network aims to build on this foundation by implementing new MPAs in areas of the coast that are vital for the survival of numerous species, including the more than 80 species at risk. Amongst at-risk species are yelloweye rockfish, bocaccio rockfish, quillback rockfish, canary rockfish, northern abalone, fin whales, humpback whales, North Pacific right whales, eulachon, and basking sharks.
Major Findings: More Fish, Bigger Fish
The UCSB-led study analyzed long-term monitoring data from MPAs spanning surf zones, kelp forests, shallow reefs, and deep reefs. Researchers found that MPAs consistently led to higher fish biomass, particularly for species that had been heavily fished before protection measures were introduced.
“If you have different habitats in proximity to each other, then there’s more variability in the types of resources, foods, shelters—the types of things fish need to survive—in the space where they’re living.”
Cori Lopazanski, doctoral student at UCSB’s Bren School of Environmental Science & Management
Older MPAs showed the most pronounced benefits, reinforcing the idea that recovery takes time, especially for slow-growing species like rockfish, which are also abundant in BC waters. MPAs with strict fishing restrictions saw the best results, confirming that stronger protections lead to healthier fish populations. Areas with diverse habitats also performed well, as they provide the necessary resources for different species to thrive.
“If you have different habitats in proximity to each other, then there’s more variability in the types of resources, foods, shelters—the types of things fish need to survive—in the space where they’re living,” said co-author Cori Lopazanski, a doctoral student at UCSB’s Bren School of Environmental Science & Management.
What This Means for British Columbia
California’s process included input from fishers, scientists, and local communities. In BC, Indigenous leadership and local stakeholder engagement have been critical in ensuring MPAs are both effective and equitable.
The development of the Great Bear Sea MPA Network uses a collaborative approach involving Indigenous leadership, governmental partnerships, and extensive community and industry consultation. In February 2023, 15 First Nations, alongside the Government of Canada and the Province of British Columbia, jointly endorsed the MPA Network Action Plan during the Fifth International Marine Protected Area Congress (IMPAC5).
With Canada committed to protecting 30% of its oceans by 2030, California’s 25-year MPA experiment provides a real-world example of how marine protection can work when properly implemented.
Check out this article to learn more.
