Global Diversity Hotspots and Conservation Priorities for Sharks

Luis O Lucifora,Boris Worm,Verónica B García,Andrew Hector

doi:10.1371/journal.pone.0019356

Abstract

Sharks are one of the most threatened groups of marine animals, as high exploitation rates coupled with low resilience to fishing pressure have resulted in population declines worldwide. Designing conservation strategies for this group depends on basic knowledge of the geographic distribution and diversity of known species. So far, this information has been fragmented and incomplete. Here, we have synthesized the first global shark diversity pattern from a new database of published sources, including all 507 species described at present, and have identified hotspots of shark species richness, functional diversity and endemicity from these data. We have evaluated the congruence of these diversity measures and demonstrate their potential use in setting priority areas for shark conservation. Our results show that shark diversity across all species peaks on the continental shelves and at mid-latitudes (30–40 degrees N and S). Global hotspots of species richness, functional diversity and endemicity were found off Japan, Taiwan, the East and West coasts of Australia, Southeast Africa, Southeast Brazil and Southeast USA. Moreover, some areas with low to moderate species richness such as Southern Australia, Angola, North Chile and Western Continental Europe stood out as places of high functional diversity. Finally, species affected by shark finning showed different patterns of diversity, with peaks closer to the Equator and a more oceanic distribution overall. Our results show that the global pattern of shark diversity is uniquely different from land, and other well-studied marine taxa, and may provide guidance for spatial approaches to shark conservation. However, similar to terrestrial ecosystems, protected areas based on hotspots of diversity and endemism alone would provide insufficient means for safeguarding the diverse functional roles that sharks play in marine ecosystems.

Highlights

To derive a global conservation strategy for higher taxa it is fundamental to know where different species occur and which geographic areas harbour high species richness, concentrations of endemic or threatened species, or unique communities of species [1]
High exploitation rates coupled with a slow life history and low resilience to fishing mortality have resulted in population declines, of large sharks, worldwide [e.g. 10–17] and pose a serious threat for the survival of many species
We have found that (1) shark species richness and endemicity are highest on continental shelves and at intermediate latitudes, (2) centers of shark species richness and endemicity tend to be geographically small, with only a few areas harbouring a disproportionately large species richness and endemicity, (3) total shark species richness, richness of finned species, endemicity and functional richness show some notable spatial differences, and (4) shark conservation may be difficult to pursue if based solely on a protected-area framework, due to the large spatial extent of conservation priority areas that represent all major biogeographic units; this is true for the conservation of highly pelagic communities in the open ocean

Summary

Introduction

To derive a global conservation strategy for higher taxa (i.e. above the species level) it is fundamental to know where different species occur and which geographic areas harbour high species richness, concentrations of endemic or threatened species, or unique communities of species [1]. Earlier studies estimated that 60 million individuals [6] or 1.35 million tonnes [7] of sharks and rays are killed globally, either in target fisheries or as unintended bycatch These numbers were based primarily on reported catches, and may still be underestimates considering that the burgeoning shark fin trade alone involved a minimum of 26 to 73 million sharks per year in the late 1990s [8], with a combined weight of 1.7 million tonnes per year (median estimate). High exploitation rates coupled with a slow life history and low resilience to fishing mortality have resulted in population declines, of large sharks, worldwide [e.g. 10–17] and pose a serious threat for the survival of many species Several management strategies, such as setting maximum allowable catches and size limits, or closing of particular areas, have been developed to conserve individual species of sharks, highly commercial ones [5,18,19,20].

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Conclusion