When accounting for the average weight of different species groups, a minimum estimate

of 49 million sharks can be derived from the FAO landings data. Yet this does not account for unreported and illegal catches. If we estimate an average rate of illegal, unregulated and unreported (IUU) fishing, we arrive at a total of 63 million sharks per year for the year 2000. This minimum estimate of global shark mortality changes only slightly from 2000 to 2010 (61 million sharks) as reported shark landings remained near-constant over the decade. This number is also similar to the upper estimate of shark mortality from the fin trade of 73 million individuals [9]. The abovementioned minimum estimate of shark mortality does not include discards and artisanal fishing Alectinib ic50 since these sources of mortality are not accounted for in the FAO and IUU data.

In the present paper these numbers are estimated for the first time. While the total catch rate of sharks in global longline fisheries could be well estimated from published data, data of similar quality for other fishing gear types that catch sharks, such as Torin 1 manufacturer purse seines, gillnets, and trawls, were not available. Hence it was estimated here (from the FAO data) that about 52% of sharks are caught by longlines, with the remaining 48% caught by all other types of gear combined. This likely underestimates the catches of sharks in other fishing gear; trawls for example can catch very large numbers of small coastal sharks, most of which are discarded [7]. Hence the estimate for total mortality including discards is still likely conservative at 100 million sharks in 2000. These calculations carry uncertainties and should be interpreted with some caution. The number of dead sharks, for example, is sensitive to the assumed percentage of small coastal sharks in the catch. If it is assumed that these are represented in the total catch (including discards) with the same proportion as in the reported and species-identified catch, the total mortality

estimate increases to 273 million sharks, which represents an upper limit of shark mortality estimated here. Another uncertain value is the shark mortality Immune system from artisanal and recreational fishing, which is only partially accounted for in this analysis, a fact that again renders the estimate of 100-million sharks killed annually conservative. Finally, the proportion of sharks that are killed for their fins is well known for the early 2000s (Table 3). However a number of regions now have anti-finning legislation that may reduce the incidence of finning and discarding of carcasses, and hence possibly reduce the mortality of sharks. Yet, despite these legislative changes there is presently no apparent sign of leveling off in the global fin trade (Fig. 1D–F). Nor is there much of a decline in the reported global catches of sharks (Fig. 1B). Several explanations may account for these observations of near-stable catches and fin trade volume.