title: Extreme Inverted Trophic Pyramid of Reef Sharks Supported by Spawning Groupers.
abstract: The extent of the global human footprint [1] limits our understanding of what is natural in the marine environment. Remote, near-pristine areas provide some baseline expectations for biomass [2, 3] and suggest that predators dominate, producing an inverted biomass pyramid. The southern pass of Fakarava atoll-a biosphere reserve in French Polynesia-hosts an average of 600 reef sharks, two to three times the biomass per hectare documented for any other reef shark aggregations [4]. This huge biomass of predators makes the trophic pyramid inverted. Bioenergetics models indicate that the sharks require ∼90 tons of fish per year, whereas the total fish production in the pass is ∼17 tons per year. Energetic theory shows that such trophic structure is maintained through subsidies [5-9], and empirical evidence suggests that sharks must engage in wide-ranging foraging excursions to meet energy needs [9, 10]. We used underwater surveys and acoustic telemetry to assess shark residency in the pass and feeding behavior and used bioenergetics models to understand energy flow. Contrary to previous findings, our results highlight that sharks may overcome low local energy availability by feeding on fish spawning aggregations, which concentrate energy from other local trophic pyramids. Fish spawning aggregations are known to be targeted by sharks, but they were previously believed to play a minor role representing occasional opportunistic supplements. This research demonstrates that fish spawning aggregations can play a significant role in the maintenance of local inverted pyramids in pristine marine areas. Conservation of fish spawning aggregations can help conserve shark populations, especially if combined with shark fishing bans.
authors.affiliation: EPHE, PSL Research University, UPVD, CNRS, USR 3278 CRIOBE, 66360 Perpignan, France; Faculty of Science and Engineering, Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia. Electronic address: johann.mourier@gmail.com.
authors.forename: Johann
authors.initials: J
authors.lastname: Mourier
authors.affiliation: EPHE, PSL Research University, UPVD, CNRS, USR 3278 CRIOBE, 66360 Perpignan, France; SymbioSeas and the Marine Applied Research Center, Wilmington, NC 28411, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Maynard
authors.affiliation: EPHE, PSL Research University, UPVD, CNRS, USR 3278 CRIOBE, 66360 Perpignan, France.
authors.forename: Valeriano
authors.initials: V
authors.lastname: Parravicini
authors.affiliation: Andromede Oceanology, Place Cassan, 34280 Carnon, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Ballesta
authors.affiliation: EPHE, PSL Research University, UPVD, CNRS, USR 3278 CRIOBE, 66360 Perpignan, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Clua
authors.affiliation: Marine Conservation Science Institute, 68-1825 Lina Poepoe Street, Waikoloa, HI 96738, USA.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Domeier
authors.affiliation: EPHE, PSL Research University, UPVD, CNRS, USR 3278 CRIOBE, 66360 Perpignan, France; Laboratoire d'Excellence CORAIL.
authors.forename: Serge
authors.initials: S
authors.lastname: Planes
mesh_terms: D063147:Animal Distribution; D000818:Animals; D001492:Bass / Q000502:physiology*; D057894:Coral Reefs; D004734:Energy Metabolism; D005247:Feeding Behavior; D020387:Food Chain; D008954:Models, Biological; D011114:Polynesia; D012754:Sharks / Q000502:physiology*