The extent of the global human footprint limits our understanding of what is natural in the marine environment. Remote near-pristine areas provide some baseline expectations for biomass 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, 2-3 times the biomass/ha documented for any other reef shark aggregations. This huge biomass of predators makes the trophic pyramid inverted. Bioenergetics models indicate the sharks require ~ 90 tons of fish/year while the total fish production in the pass is ~ 17 tons/year. Energetic theory shows that such trophic structure is maintained through subsidies and empirical evidence suggests sharks must engage in wide ranging foraging excursions to meet energy needs. We used underwater surveys and acoustic telemetry to assess shark residency in the pass and feeding behavior, and 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 were previously believed to play a minor role representing occasional opportunistic supplements. This research demonstrates fish spawning aggregations can play a significant role in the maintenance of local inverted pyramids in pristine marine areas. Conserving fish spawning aggregations can help conserve shark populations, especially if combined with shark fishing bans.