Largest global shark biomass found in the northern Galápagos Islands of Darwin and Wolf.

Pelayo Salinas De León,Etienne Rastoin,Enric Sala,David Acuña-Marrero,Mary K Donovan,Alan M Friedlander

doi:10.7717/peerj.1911

Pelayo Salinas De León, Etienne Rastoin + Show 4 more

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https://doi.org/10.7717/peerj.1911

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Abstract

Overfishing has dramatically depleted sharks and other large predatory fishes worldwide except for a few remote and/or well-protected areas. The islands of Darwin and Wolf in the far north of the Galapagos Marine Reserve (GMR) are known for their large shark abundance, making them a global scuba diving and conservation hotspot. Here we report quantitative estimates of fish abundance at Darwin and Wolf over two consecutive years using stereo-video surveys, which reveal the largest reef fish biomass ever reported (17.5 t n}{}{mathrm{ha}}^{-1} on average), consisting largely of sharks. Despite this, the abundance of reef fishes around the GMR, such as groupers, has been severely reduced because of unsustainable fishing practices. Although Darwin and Wolf are within the GMR, they were not fully protected from fishing until March 2016. Given the ecological value and the economic importance of Darwin and Wolf for the dive tourism industry, the current protection should ensure the long-term conservation of this hotspot of unique global value.

Highlights

Sharks and other top reef predators dominate healthy marine ecosystems, so that the traditional fish biomass pyramid is inverted in these increasingly rare areas (Friedlander & DeMartini, 2002; Sandin et al, 2008; Sandin et al, 2015)
Biomass was similar between years (2013 = 19.3 ± 18.9; 2014 = 15.6 ± 19.5) but was significantly different due to the large year x orientation owing to higher biomass in the NW in at both islands (Fig. 2, Table 1)
The first quantitative fish surveys using the stereo-video approach around Darwin and Wolf islands revealed the largest fish biomass reported to date on a reef worldwide (Fig. 4)

Summary

Introduction

Sharks and other top reef predators dominate healthy marine ecosystems, so that the traditional fish biomass pyramid is inverted in these increasingly rare areas (Friedlander & DeMartini, 2002; Sandin et al, 2008; Sandin et al, 2015). A growing body of literature supports the positive effects of NTA, which includes substantial recoveries in fish abundance and biomass (Aburto-Oropeza et al, 2011; Eddy, Pande & Gardner, 2014); a greater biomass, abundance and size of top predators inside reserves than in nearby fished areas (see review by Lester et al, 2009); increase in abundance and biomass in nearby areas due to the spill-over of adults and/or larvae (Goñi et al, 2008; Halpern, Lester & Kellner, 2009; Christie et al, 2010), and shifts in species composition and trophic cascades that result in the restoration of entire ecosystems (Babcock et al, 1999, 2010; Shears & Babcock, 2002, 2003).

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