A paper in the Current Biology Journal describes the “inverted trophic pyramid” that exists at the South Pass at Fakarava, French Polynesia. Between 250 to 700 grey reef sharks (Carcharhinus amblyrhynchos) inhabit the area thanks to the grouper spawning aggregations that occur in the pass.
These seasonal concentrations of fish allow for a much higher population density of sharks that would otherwise be possible. However, it also makes the area very vulnerable to overfishing as if the groupers are overfished, the sharks will be unable to sustain their population.
Chief researcher, Johan Mourier has posted this video describing the paper’s findings: