Skip to main content

## Search

My Visit

Donate

Smithsonian Institution

## Site Navigation

- Visit   - Hours and Locations
  - Entry and Guidelines
  - Maps and Floor Plans
  - Dining and Shopping
  - Accessibility
  - Visiting with Kids
  - Group Visits     - Group Sales
- What's On   - Exhibitions     - Current
    - Upcoming
    - Past
  - Today's Events
  - Online Events
  - All Events
  - IMAX & Planetarium
- Explore   - Art & Design
  - History & Culture
  - Science & Nature
  - Collections     - Open Access
  - Research Resources     - Libraries
    - Archives       - Smithsonian Institution Archives
      - Air and Space Museum
      - Anacostia Community Museum
      - American Art Museum
      - Archives of American Art
      - Archives of American Gardens
      - American History Museum
      - American Indian Museum
      - Asian Art Museum Archives
      - Eliot Elisofon Photographic Archives, African Art
      - Hirshhorn Archive
      - National Anthropological Archives
      - National Portrait Gallery
      - Ralph Rinzler Archives, Folklife
      - Libraries' Special Collections
  - Podcasts
  - Mobile Apps
- Learn   - For Caregivers
  - For Educators     - Art & Design Resources
    - Science & Nature Resources
    - Social Studies & Civics Resources
    - Professional Development
    - Events for Educators
    - Field Trips
  - For Students
  - For Academics
  - For Lifelong Learners
- Get Involved   - Volunteer     - Behind-the-Scenes
    - Digital Volunteers
    - Smithsonian Call Center
    - Visitor Information Specialist
    - Docent Programs
  - Citizen Science
  - Work with Us     - Office of Human Resources       - Working Here
      - Employee Benefits
      - How to Apply
      - Job Opportunities
      - Job Seekers with Disabilities
      - Frequently Asked Questions
      - SI Civil Program
      - Contact Us
    - Affiliations
    - Global Partners
- Support   - About Membership
  - Become a Member
  - Renew Your Membership
  - Make a Gift
- About   - Museums and Zoo
  - Research Centers
  - Cultural Centers
  - Education
  - Our Organization     - Leadership       - Secretary Bunch
      - Advancement
      - Communications
      - Administration
      - Education
      - Museums and Culture
      - Science and Research
    - Board of Regents       - Members
      - Committees
      - Reading Room
      - Bylaws, Policies and Procedures
      - Contact
      - Schedules and Agendas
      - Meeting Minutes
      - Actions
      - Webcasts
    - General Counsel       - Legal History
      - Internships
      - Records Requests         - Reading Room
      - Tort Claim
      - Subpoenas & Testimonies
      - Events
    - Equal Employment Office       - EEO Complaint Process
      - Individuals with Disabilities
      - Special Emphasis Program
      - Supplier Diversity Program         - Doing Business with Us
        - Policies and Procedures
        - Additional Resources
    - Sponsored Projects       - Policies         - Animal Care and Use
        - Human Research
      - Reports
      - Internships
  - Reports and Plans     - Annual Reports
    - Metrics Dashboard       - Dashboard Home
      - Virtual Smithsonian
      - Public Engagement
      - National Collections
      - Research
      - People & Operations
      - One Smithsonian
    - Strategic Plan
  - Newsdesk     - News Releases
    - Media Contacts
    - Photos and Video
    - Media Kits
    - Fact Sheets
    - Visitor Stats
    - Secretary and Admin Bios
    - Filming Requests

# Adult Fish Struggle To Bounce Back in Marine Protected Areas

                  - Share IconShare Icon                     - 
                    - 
                    - 
                    - 
                    -
                  -                     - 
                    - Print
                    -     
Bluestriped grunts swim around a reef in Hol Chan Marine Reserve, Belize. Credit: Luciano Candisani /iLCP.

Age matters when determining how to protect life in the ocean; every population needs a strong cohort of adults to produce the next generation. But many marine protected areas (MPAs) are falling short of their most basic purpose: to rebuild struggling fish populations. In a new study published April 4 in Global Change Biology, scientists looked at the age breakdown of reef fish in marine protected areas for the first time. They discovered in almost all of them, adult fish populations have either flatlined or declined.

“Adult fish are really important,” said Steve Canty, marine ecologist with the Smithsonian Environmental Research Center and a lead author of the study. “They are the primary catch within commercial fisheries that support livelihoods and food security of coastal communities. Additionally, it is the adults that breed and rebuild the fisheries, and here size matters. Bigger and older female fish produce more and better eggs, and therefore are critical to rebuilding fish populations.”  

It is a vital lesson as the world races to meet the “30 by 30” target to conserve 30% of Earth’s ocean by 2030. Delegates at the United Nations Biodiversity Conference set that ambitious goal in December 2022. However, many experts say the target will mean little unless nations choose sites where marine life can flourish and balance the needs of coastal communities.

The study looked at fish in the Mesoamerican Reef. The longest reef in the Western Hemisphere, it stretches over 600 miles along the coasts of southern Mexico, Belize, Guatemala and Honduras. The region is a biodiversity hotspot, home to over 500 fish species, 60 kinds of corals and one of the largest whale shark congregations on Earth. The marine resources of the region also support the livelihoods and food security of over 1 million people.

The scientists examined adult versus juvenile fish biomass in 139 reef sites—111 protected and 28 unprotected. Protected sites in the Mesoamerican Reef fall into three categories: “fully protected areas” where fishing is completely banned, “highly protected areas” that allow activities like subsistence and catch-and-release sport fishing and “general use zones” where commercial fishing is often allowed but specific methods or equipment are banned. Of the marine protected areas in the study, a mere 24% were either fully or highly protected.

“It’s always difficult to prohibit fishing from any part of the sea—as if it goes against a basic human instinct,” said Melanie McField, co-author and director of the Healthy Reefs Initiative. “But fully protecting and enforcing these areas is the best way to grow bigger fish that can rebuild the populations and actually increase overall fish catches outside the fully protected areas.”

The team took their fish biomass data from the Healthy Reefs Initiative, which uses scuba divers to survey fish at hundreds of reefs throughout the region. The initiative has also evaluated the four countries in the Mesoamerican Reef for enforcement and other management practices in protected sites. The study included additional data about coastal development, sea surface temperature and other key variables known to affect fish populations. The scientists looked at data over a 12-year timeframe, from 2006 to 2018.

The results were troubling. Though marine protected areas exist largely to rebuild fish populations, only 11 sites in the study—8% total—saw significant increases in adult biomass. Most sites saw no change, and 28 sites saw declines. The sites with declines had several things in common: They all had heavy coastal development nearby and experienced high levels of warming in their waters. They were also all in general use zones—the weakest type of marine protected area—and even then had only “inadequate or moderate enforcement.”

“Minimal protection in the weakest MPAs proved to be more detrimental than no protection at all, because it allowed for continued and concentrated exploitation without effective management,” said co-author Abel Valdivia, marine conservation scientist with the World Wildlife Fund. “Unlike open-access zones, where fishing pressure may be spread out, weakly protected areas faced unchecked coastal development, warming waters and inadequate enforcement, leading to the decline in adult biomass.”

However, the 11 sites where adults rebounded also had some common trends. They were all in fully protected areas with adequate enforcement, experienced fewer sea surface temperature spikes and were beside areas with a lower human footprint.

This 12-year snapshot of the Mesoamerican Reef offers clues for how the rest of the globe can succeed at “30 by 30” conservation. Strong enforcement and effective management are key to a marine protected area’s success, as is community buy-in and support. Choosing sites with climate change in mind is also critical, the authors said. While many parts of the ocean cannot escape warming waters, sites that could act as climate refuges for both adult and juvenile life stages need to be top candidates for full protection.

“Our study shows that adults and juvenile fish respond very differently to management and environmental change,” said Justin Nowakowski, a lead author and ecologist with the Smithsonian Environmental Research Center. “Adults were more sensitive to stressors like climate change, which can undermine the local benefits of MPAs. The big question now is where to locate new MPAs to maximize positive impacts for the regional fishery. To do this, we need to consider the unique requirements of adult and juvenile life stages—otherwise we are missing the full picture.”

The Smithsonian Marine Station, Conservation International, Barefoot Ocean, Louisiana State University and the University of Maryland Center for Environmental Science also contributed to the study. The article will be available after publication on the journal’s website. For photos, an advance copy of the study or to speak with one of the authors, contact Kristen Goodhue at goodhuek@si.edu.

# # #

SI-118-2024
Media Only
Kristen Goodhue

443-482-2325

GoodhueK@si.edu
Smithsonian Environmental Research CenterResearch News   Newsdesk- News Releases
- Media Contacts
- Photos and Video
- Media Kits
- Fact Sheets
- Visitor Stats
- Secretary and Admin Bios
- Filming Requests
            Search Newsdesk          Search      Media Events      Anacostia Community Museum Celebrates Earth Day With Daylong ActivitiesSat., Apr. 20, 2024 10:00 am - 5:00 pmSubscribe
 Newsdesk RSS Research News RSS
         Media      -    George StoyleSchoolmaster Snapper
Schoolmaster snapper swim around a coral reef in Honduras.
Download(4.98 MB) 
-    Pete Oxford/iLCPBluestriped Grunts & Gray Snapper
Bluestriped grunts and gray snapper, two fish species vital to the local economy, in Belize’s Hol Chan Marine Reserve.
Download(11.36 MB) 
-     George StoyleJuvenile Grunts
Juvenile grunts school in a reef in Honduras. In the study, juvenile fish did better at sites with high coral cover. 
Download(10.26 MB) 
-     Luciano Candisani /iLCPHol Chan Marine Reserve Bluestriped Grunts
Bluestriped grunts swim around a reef in Hol Chan Marine Reserve, Belize.
Download(11.55 MB) 
          Footer logo      
Link to homepage
      Footer navigation      - Contact Us
- Accessibility
- Job Opportunities
- Inspector General
- Records Requests
- EEO & Supplier Diversity
- Shop Online
- Host Your Event
- Press Room
- Privacy
- Terms of Use
      Social media links      - Facebook
- Instagram
- Twitter
- YouTube
      Email signup form      Yes, I would like to receive email from the Smithsonian.Deny submitSign up for Smithsonian e-news:        Email powered by BlackBaud (Privacy Policy, Terms of Use)  Back to Top