CIE Peer Review

Subject Shark Predation Mitigation as a Tool for Conservation of the Hawaiian Monk Seal
Document(s) Reviewed
Gobush KS
2010. Shark Predation on Hawaiian Monk Seals: Workshop II & Post-Workshop Developments, November 5-6, 2008. NOAA Technical Memorandum NMFS-PIFSC-21.
Download (3.6 MB PDF)
Harting AL
2010. Shark Predation on Hawaiian Monk Seals Workshop Honolulu, Hawaii. January 8-9, 2008. Pacific Islands Fisheries Science Center. PIFSC Administrative Report H-10-02C.
Download (0.5 MB PDF)
Date December 2011

The Hawaiian monk seal population, declining steadily at over 4% per year, is heading toward extinction unless survival of the seals, particularly pups, is increased significantly. The seal population faces many threats. At French Frigate Shoals (FFS), one of the primary breeding sites in the Northwestern Hawaiian Islands (NWHI), the major threat is shark predation in nearshore waters on preweaned and newly weaned monk seal pups. A high incidence of pup loss to sharks sets FFS apart from other sites in the NWHI. Since peaking during 1997–1999, pup predation at FFS has declined to 6-11 pups a year, still an unsustainable rate as a result of falling birth rates. Potential monk seal predators at FFS include Galapagos sharks (Carcharhinus galapagensis) and tiger sharks (Galeocerdo cuvier). However, PIFSC scientists in the Hawaiian Monk Seal Research Program (HMSRP) have only observed Galapagos sharks attacking and killing FFS pups.

Over the last decade, HMSRP personnel have carried out a multi-faceted program at FFS to mitigate predation by sharks, including: intensive observation of sharks, harassment of sharks, translocation of weaned pups from FFS to other sites, deployment of devices to deter shark predation, and removal of sharks. Decisions to remove sharks must weigh many factors, such as the number an identity of sharks likely involved, wariness of sharks to human activity, and varying opinions about shark culling in a broader ecosystem context. PIFSC activities to mitigate predation by sharks have been guided by peer-reviewed science, inference, expert opinion, and the extensive experience of staff scientists at FFS. The issuance of permits required to remove sharks from FFS waters is a sensitive issue for managers, particularly since the NWHI are part of the Papahānaumokuākea Marine National Monument.

Decisions to permit shark removals must be supported by solid, peer-reviewed science. To ensure proper peer review of the science underlying the shark predation mitigation project, PIFSC solicited the services of the Center for Independent Experts (CIE). The CIE engaged 3 reviewers and charged them with conducting independent evaluations of documents that have guided shark removal actions so far. In addition to reviewing 2 primary PIFSC documents (listed above), the CIE experts were provided with additional pertinent background scientific literature.

Each CIE reviewer was asked to conduct an impartial and independent peer review. Under the Terms of Reference for the peer review, reviewers were charged with evaluating PIFSC practices in the FFS shark removal project as described in the review documents and issuing their findings and recommendations on a broad range of topics. These included:

  1. Data collection operations
  2. Data quality
  3. Analytic methodologies, including strengths and weaknesses
  4. Assumptions, estimates, and uncertainty
  5. Interpretation and conclusions by PIFSC scientists concerning certain points, namely:
    1. The Hawaiian monk seal population is significantly impacted by predation on pups.
    2. The primary species of shark involved in predation of seal pups is the Galapagos shark.
    3. A relatively small number of sharks are responsible for the majority of pup predation.
    4. Removing a small number of large/adult Galapagos sharks targeted in the nearshore areas near pupping islets has the potential of mitigating the predation issue.
    5. Removing 20-40 Galapagos sharks is unlikely to cause neither significant deleterious impacts on that species' population at FFS nor any other unintended ecosystem consequences.
    6. The methods used to monitor shark activity and monk seal pups are adequate to characterize the level of predation.
    7. The methods used to study shark movement patterns represent the best available to understand the ecology of multiple shark species at FFS.
    8. The influence of possible covariates of predation have been adequately analyzed.
    9. The involvement of tiger sharks in the predation issue?
    10. The Galapagos sharks display site-specific movement patterns versus wide-ranging movement patterns.

Each reviewer was also to determine whether the science reviewed is considered to be the best scientific information available and to provide recommendations for further improvements of the project.

The final reports of the CIE reviewers were forwarded by the CIE to PIFSC in December 2011. The reviewer reports are provided here in PDF format.

The findings and recommendations of the CIE reviewers are being carefully examined and considered as PIFSC addresses future research plans and monk seal recovery strategies at FFS.

— Samuel G. Pooley, Director

Reviewer Comments

Dr. John Harwood
Comments (0.2 MB PDF)

Dr. Francesco Ferretti
Comments (0.3 MB PDF)

Dr. Leah Gerber
Comments (0.2 MB PDF)