Re‐Creating Missing Population Baselines for Pacific Reef Sharks

Abstract

Sharks and other large predators are scarce on most coral reefs, but studies of their historical ecology provide qualitative evidence that predators were once numerous in these ecosystems. Quantifying density of sharks in the absence of humans (baseline) is, however, hindered by a paucity of pertinent time‐series data. Recently researchers have used underwater visual surveys, primarily of limited spatial extent or nonstandard design, to infer negative associations between reef shark abundance and human populations. We analyzed data from 1607 towed‐diver surveys (>1 ha transects surveyed by observers towed behind a boat) conducted at 46 reefs in the central‐western Pacific Ocean, reefs that included some of the world's most pristine coral reefs. Estimates of shark density from towed‐diver surveys were substantially lower (

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