Shark Declines: Fuel for a Decade of Conservation Effort

Shark Declines: Fuel for a Decade of Conservation Effort

by Austin J. Gallagher & Neil Hammerschlag



Scientists have been studying the population status of sharks for years and while the vulnerability, threatened status and biological importance of sharks has long-been well-recognized and documented by the research community (1), ten years ago, shark conservation was catapulted in the public spotlight after the highly publicized report, titled “Collapse and conservation of shark populations in the northwest Atlantic” by Baum and colleagues (2), in the journal Science. By using fisheries logbook data, this paper presented shocking and significant changes in abundance for many species of shark off the Northwest Atlantic over multiple decades.

While the data-analysis and magnitude of the declines reported within Baum et al. (2), and the subsequent Baum and Myers (3), have been challenged (4), the former article has been cited in the scientific literature a total of 685 times since its publication (Google Scholar, 17 Sept 2013). The paper was the beginning of a series of similar studies, to name just a few, showing patterns of shark declines in the Indian (5), Pacific (6, 7), Northwest Atlantic and Gulf of Mexico (8, 9) and Mediterranean ocean basins (10), while sharks have also been reported to be largely absent throughout the Caribbean (11). Moreover, recent work utilizing different data sources assessing changes in abundance has documented similar patterns of declines in the Gulf of Mexico (12), as well as shifting baselines of predator biodiversity in the Central Pacific (13). The declines in many shark populations over the past decades have also generated species-specific risk and threat analyses (i.e., ecological risk assessment, stock assessment, IUCN Red Listing (14, 15, 16).

Paralleling the pace in the research community has been the rise of the global shark conservation advocacy movement, a social phenomenon fueled by increased digital access to science and interactions via social media (17). Due to the magnitude and increased awareness of shark declines reported by various studies over the past decade as well as the media attention that has been generated from these publications, the take home message that has seemed to resonate with the public is that populations of shark species are drastically declining globally, despite not all shark populations being a cause for concern.

As the threats imposed on shark species continue to become better understood, technologies for studying shark behavior and conservation also continue to evolve rapidly. For example, there continues to be development of non-lethal methodologies for studying threatened shark species (18). Collaborations between national authorities, the public and scientific communities have also been creating shark-specific marine protected areas known as shark sanctuaries. In addition, there is a recent push towards utilizing sharks as a non-consumptive resource through diving ecotourism, a widespread and economically important industry that is now one of the strongest contemporary arguments for their protection (19). Over the next decade, shark conservation efforts will continue to shift its focus from largely describing shark declines to finding and implementing tangible solutions.

An Oceanic Whitetip shark cruises in for a close look
An Oceanic Whitetip shark cruises in for a close look



Literature Cited

1) Stevens JD, Bonfil R, Dulvy NK, Walker PA. 2000. The effects of fishing on sharks, rays, and chimaeras (chondrichthyans), and the implications for marine ecosystems. ICES J Mar Sci 57:476–494.

2) Baum JK, Myers RA. 2004. Shifting baselines and the decline of pelagic sharks in the Gulf of Mexico. Eco Lett 7:135–145.

3) Baum JK, et al. 2003. Collapse and conservation of shark populations in the Northwest Atlantic. Science 299:389–392.

4) Burgess GH, et al. 2005. Is the collapse of shark populations in the Northwest Atlantic Ocean and Gulf of Mexico real? Fisheries 30:19–26.

5) Graham NAJ, Spalding MD, Sheppard CRC. 2010. Reef shark declines in remote atolls highlight the need for multi-faceted conservation action. Aquat Cons: Mar Fresh Ecosyst 20:543-548.

6) Robbins WD, Hisano M, Connolly SR, Choat JH. 2006. Ongoing collapse of coral-reef shark populations. Curr Biol 16:2314-2319.

7) Nadon MO, et al. 2012. Recreating missing population baselines for pacific reef sharks.         Cons Biol 26:493-503.

8) Shepherd TD, Myers RA. 2005. Direct and indirect fishery effects on small coastal       elasmobranchs in the northern Gulf of Mexico. Eco Lett 8:1095–1104

9) Myers R A, Baum JK, Shepherd TD, Powers SP, Peterson CH. 2007. Cascading effects of the loss of apex predatory sharks from a coastal ocean. Science 315:1846-50. 

10) Ferretti F, Myers RA, Serena F, Lotze HK (2008) Loss of large predatory sharks from the Mediterranean Sea. Cons Biol 22:952–64

11) Ward-Paige CA, Mora C,  Lotze HK, Pattengill-Semmens C, McClenachan L, et al. 2010.      Large-scale absence of sharks on reefs in the greater-Caribbean: a footprint of humanpressures. PloS ONE 5:e11968.

12) Powers SP, et al. 2013. Gulf-wide decreases in the size of large coastal sharks documented by    10) Ferretti F, Myers RA, Serena F, Lotze HK (2008) Loss of large predatory sharks from the Mediterranean Sea. Cons Biol 22:952–64

13) Drew J, Phillip C, Westneat MW. 2013. Shark tooth weapons from the 19th century reflect shifting baselines in Central Pacific predator assemblies. PLoS ONE 8:e59855.

14) Dulvy N, et al. .2008. You can swim but you can’t hide: the global status and conservation of oceanic pelagic sharks and rays. Aquat Cons: Mar Fresh Ecosyst 482:459–482.

15) Cortés E., et al. 2010 Ecological risk assessment of pelagic sharks caught in Atlantic pelagic longline fisheries. Aquat Liv Res 23:25–34.

16) Gallagher AJ, Kyne PM, Hammerschlag N. 2012. Ecological risk assessment and its application to           elasmobranch conservation and management. J Fish Biol 80:1727–1748.

17) Darling E, Shiffman D, Drew J, Cote I. 2013. The role of twitter in the life cycle of a scientific publication. Ideas Eco Evo 6:32-43.

18) Hammerschlag N, Sulikowski J. 2011. Killing for conservation: the need for alternatives to           lethal sampling of apex predatory sharks. Endang Spec Res 14:135-140.

19) Gallagher AJ, Hammerschlag N. 2011. Global shark currency: The distribution, frequency,  and socio-economics of shark ecotourism. Curr Issues Tour 14:797-812.

Research Associate Professor at the University of Miami, Rosenstiel School of Marine & Atmospheric Science Dedicated to advancing marine conservation through research, education and outreach Views my Own
  • Nick Dulvy

    Awareness of the plight of sharks and rays began long before the Baum et al. paper in 2003. Sure other peer-reviewed papers heavily cite this regional paper, but while peer-review is the currency of academia it is not the currency of conservation action and lasting change. By contrast, the global scale IUCN Red List Assessments of sharks and rays garner a minimum of 170,000 page views each year, and have laid the foundation for recent CITES and CMS listings and changed practices of the airline industry.

    There were some earlier warnings of impending population collapses, notably by Mike Holden in the UK. But the tipping point for many in the field began with convergence of thinking resulting from three distinct activities in the early 1990s. Repeat observations of decline and collapse galvanized scientists at the Sharks Down Under conference in Sydney, Australia in 1991, this coincided with the seminal publication in Conservation Biology of a clarion call by Manire and Gruber in 1991 entitled, ” Many Sharks Could Be Headed to Extinction”. The few citations this paper has belies it’s massive impact on the thinking of conservation scientists. The third lasting action, enabled by the other two, was the creation of the Shark Specialist Group of the International Union For the Conservation of Nature in 1991 by Simon Stuart with Sonny Gruber and Sarah Fowler as Co-Chairs. It was this coalescence of consensus that set the scene for the subsequent two-decades of conservation and fisheries effort that most recently culminated in the recent CITES listings of commercially exploited sharks and rays, for the first time, this year.

  • Patrick Nason

    Thank you for pulling these references together. I might add that while the discourse of shark conservation in academia is a few decades old, the cultural interest in preserving shark populations dates much earlier to the writing of Rachel Carson, Jacques Cousteau, and we might even say, more provocatively, Peter Benchley. Like it or not, Jaws made us aware of sharks, the first step of activism and the seed of scientific inquiry. Whether that attention followed the ethic of Quint or that of Hooper is a much longer story.

  • Nick

    Thanks for sharing your comments.

    As we discussed, dating at least as far back as the 30’s, there is a rich history of shark conservation efforts by many, including some unsung heros, that have worked hard and have impacted policy.

    Part of the point we were trying to make is that as social media developed over the last decade, and rapid communication of ideas, we believe that the Baum paper resonated with the public, causing a new public conscious of shark declines. Moreover, rather than focusing on declines to fuel conservation efforts,the next decade will need to continue focusing on tangible solutions to promote resilience and recovery of threatened stocks.

    As we discussed on the phone, it would be really interesting (and useful) to determine how and track which scientific papers have contributed to direct conservation policy!

  • Anonymous

    Thanks to Neil and Austin for a great article. The body of work described, in particular Baum et al. 2003 paper had a great influence on my choice to become a shark researcher. It is clear there are many shark biologists and conservation biologists who made important contributions prior to this time, and continue to do so today. Highlighting an individual who has done exemplary work should not (and I don’t think does in this case) in any way diminish the past work of others.

    — Note: A portion of this comment was censored —

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