Abstract
Coral reef habitats in the Papahānaumokuākea Marine National Monument (PMNM) are characterized by abundant top-level predators such as sharks and jacks. The predator assemblage is dominated both numerically and in biomass by giant trevally (Caranx ignobilis) and Galapagos sharks (Carcharhinus galapagensis). A lower diversity of predatory teleosts, particularly groupers and snappers, distinguishes the PMNM from other remote, unfished atolls in the Pacific. Most coral reef top predators are site attached to a “home” atoll, but move extensively within these atolls. Abundances of the most common sharks and jacks are highest in atoll fore reef habitats. Top predators within the PMNM forage on a diverse range of prey and exert top-down control over shallow-water reef fish assemblages. Ecological models suggest ecosystem processes may be most impacted by top predators through indirect effects of predation. Knowledge gaps are identified to guide future studies of top predators in the PMNM.
Highlights
Large predators are becoming scarce on many coral reefs, with fishing thought to be a major factor in declines [1,2,3,4,5,6,7]
Ecological models suggest ecosystem processes may be most impacted by top predators through indirect effects of predation
We review what is currently known about top predator ecology in the Papahanaumokuakea Marine National Monument (PMNM) and identify important knowledge gaps that limit our understanding of this ecosystem
Summary
Large predators are becoming scarce on many coral reefs, with fishing thought to be a major factor in declines [1,2,3,4,5,6,7]. These shifts appear to favor algaldominated reefs populated by small planktivorous fishes and echinoderms, at the expense of reef-building scleractinian corals [2, 6, 16, 19] These studies indicate that effective conservation of top level predators is important for coral reef ecosystem health. Empirical data from areas in which predator ecology is minimally impacted by humans would be useful for determining how we have altered predator ecology in heavily impacted areas and for setting management goals to help restore predator populations and ecosystem function One such minimally impacted area is the Papahanaumokuakea Marine National Monument (PMNM) in the Northwestern Hawaiian Islands. We review what is currently known about top predator ecology in the PMNM and identify important knowledge gaps that limit our understanding of this ecosystem
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