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Marine Ecology Progress Series

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MEPS 736:93-105 (2024)  -  DOI:

Incorporating environmental factors is critical for determining conservation baselines for relative abundance of sharks on coral reefs

Naomi F. Farabaugh1,*, Mark E. Bond1, Demian Chapman1,2, Eric Clua3, Alastair R. Harborne1, Michelle Heupel4,5, Jeremy J. Kiszka1, Michael R. Heithaus1

1Institute of Environment, Department of Biological Sciences, Florida International University, North Miami, FL 33181, USA
2Sharks and Rays Conservation Program, Mote Marine Laboratory, Sarasota, FL 34236, USA
3Paris Science et Lettres, Labex Corail, CRIOBE UAR3278 EPHE-CNRS-UPVD, Baie Opunohu, 98729 Papetoai, Moorea, French Polynesia
4Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania 7004, Australia
5Australian Institute of Marine Science, Townsville, Queensland 4810, Australia
*Corresponding author:

ABSTRACT: Populations of sharks, including those inhabiting coral reefs, have experienced dramatic global declines. Setting appropriate targets for restoring reef shark populations requires estimates of expected relative abundances in the absence of intense fishing. It is therefore important to identify factors that drive the carrying capacity of sharks in relatively intact reef systems and to determine whether expected shark abundance varies according to easy to assess variables. These variables could then be used by managers for setting restoration targets, or prioritizing resource allocation, for particular areas in the absence of detailed data. French Polynesia, the world’s largest shark sanctuary, provides a model system for addressing this question. We used baited remote underwater video surveys to assess relative abundance of sharks on 35 reefs across the broad geographic range of French Polynesia. Boosted regression tree models revealed that relative abundance of sharks varied significantly with island geomorphology. Overall, relative shark abundances at high islands were nearly 3 times lower than on atolls, and among atoll geomorphology types, open atolls had abundances nearly 20% higher than closed atolls. Island group, temperature, and net primary productivity had more limited effects. Human pressure (measured as market gravity) was not a significant factor. Although species-specific patterns varied, our findings suggest that environmental factors, particularly island geomorphology, should be taken into account when setting shark abundance recovery targets. Using this easy to assess factor can facilitate the allocation of conservation effort and improve assessments of species recovery efforts for islands in the Indo-Pacific region.

KEY WORDS: Baited remote underwater video stations · BRUVS · Carrying capacity · Biogeography · Marine predator · Marine conservation · Shark sanctuary · Boosted regression trees · Marine protected areas

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Cite this article as: Farabaugh NF, Bond ME, Chapman D, Clua E and others (2024) Incorporating environmental factors is critical for determining conservation baselines for relative abundance of sharks on coral reefs. Mar Ecol Prog Ser 736:93-105.

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