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Patterns and ecosystem consequences of shark declines in the ocean.
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The Global Shark Assessment

Dr. Ransom A. Myers (RAM) and colleagues launched the Global Shark Assessment in 2003 to assess how global shark populations have changed since the beginning of industrial scale fishing, and to make predictions about how these populations respond to global climate change and to different methods of fishing.

"Sharks are in trouble worldwide," said RAM, the Killam Chair of Ocean Studies at Dalhousie University from 1997 until his passing in 2007 (RAMlegacy website). "For these animals to survive, we need to reduce fishing effort by half and have a global ban on shark finning. We need to find out how general shark declines are across all the world's oceans."

Sharks (and other elasmobranches) are vulnerable to fishing pressure because they are long-lived, slow to mature, and produce few offspring compared with most other fish. Hence, directed fishing can decimate sharks much faster than other fish species. Sharks are frequently not the targeted fish and are taken as bycatch. In these fisheries, the slow-to-reproduce sharks may be fished towards extinction, while the more productive fishes continue to drive the industry.

For the Global Shark Assessment, shark biologists teamed up with modeling and statistical experts to take advantage of the substantial amounts of unanalyzed data on sharks. Trends were established by comparing "Historical Baselines", obtained from historical sources including exploratory research cruises, old fisher's logbooks and archived narratives, to contemporary sources such as scientific surveys, scuba divers' observations and fishery logs. Vulnerability to even light levels of fishing pressure and catch-and-release fishing were examined using life history traits (reproductive rates) and feeding habits. And, the integral role of sharks in marine ecosystems was established by exploring the abundance, distribution and behaviour of other marine animals in response to the presence and absence of sharks. This work was published in peer-reviewed scientific journals and received international media coverage.

The potential benefits of shark conservation are extensive. By protecting sharks, a particularly vulnerable group of species, shark conservation offers the opportunity to protect the myriad of other species and ecosystems with which sharks interact. Hence, at stake are not merely sharks, but our still vastly misunderstood marine realm.

Although the Global Shark Assessment project is now finished, many spin-off projects are currently active in assessing the state of shark populations around the world (People & Projects). Visit our Publications page to see some of the work that was produced from the Global Shark Assessment project.