Large–Scale Movement and Reef Fidelity of Grey Reef Sharks

Michelle R. Heupel,Richard Fitzpatrick,Colin A. Simpfendorfer,Richard Kazimierz Frank Unsworth

doi:10.1371/journal.pone.0009650

Abstract

Despite an Indo-Pacific wide distribution, the movement patterns of grey reef sharks (Carcharhinus amblyrhynchos) and fidelity to individual reef platforms has gone largely unstudied. Their wide distribution implies that some individuals have dispersed throughout tropical waters of the Indo-Pacific, but data on large-scale movements do not exist. We present data from nine C. amblyrhynchos monitored within the Great Barrier Reef and Coral Sea off the coast of Australia. Shark presence and movements were monitored via an array of acoustic receivers for a period of six months in 2008. During the course of this monitoring few individuals showed fidelity to an individual reef suggesting that current protective areas have limited utility for this species. One individual undertook a large-scale movement (134 km) between the Coral Sea and Great Barrier Reef, providing the first evidence of direct linkage of C. amblyrhynchos populations between these two regions. Results indicate limited reef fidelity and evidence of large-scale movements within northern Australian waters.

Highlights

Conservation concerns about the status of coral reef associated shark populations in various locations around the world [1,2,3,4] make it increasingly important to understand the movements and ecology of these species
In February 2008 nine C. amblyrhynchos ranging from 84–152 cm total length (TL) were fitted with acoustic transmitters in the Ribbon Reefs (Figure 1) including four males and five females (Table 1)
Individual C. amblyrhynchos monitored in the Ribbon Reefs showed variability in movement patterns

Summary

Introduction

Conservation concerns about the status of coral reef associated shark populations in various locations around the world [1,2,3,4] make it increasingly important to understand the movements and ecology of these species. Randall [5] suggested that since reef sharks are widely distributed throughout the Indo-Pacific they must make large-scale movements at some points ( these events may be rare). This suggests potentially complex patterns where some individuals are site attached while others make largescale dispersal movements, but there are no direct data for most species. Recent studies have revealed higher relative abundances of reef sharks in areas closed to fishing and public entry [1,2,4] These results suggest that area closures are supporting larger populations of site attached reef sharks, while fished regions have been locally depleted. The aims of this study were to: 1) determine the level of fidelity to individual reef platforms and marine protected areas, 2) examine the extent of movement within a series of closely associated reef platforms, and

Objectives

Methods

Results

Conclusion