Abstract
Overfishing is the primary cause of marine defaunation, yet declines in and increasing extinction risks of individual species are difficult to measure, particularly for the largest predators found in the high seas1,2,3. Here we calculate two well-established indicators to track progress towards Aichi Biodiversity Targets and Sustainable Development Goals4,5: the Living Planet Index (a measure of changes in abundance aggregated from 57 abundance time-series datasets for 18 oceanic shark and ray species) and the Red List Index (a measure of change in extinction risk calculated for all 31 oceanic species of sharks and rays). We find that, since 1970, the global abundance of oceanic sharks and rays has declined by 71% owing to an 18-fold increase in relative fishing pressure. This depletion has increased the global extinction risk to the point at which three-quarters of the species comprising this functionally important assemblage are threatened with extinction. Strict prohibitions and precautionary science-based catch limits are urgently needed to avert population collapse6,7, avoid the disruption of ecological functions and promote species recovery8,9.
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Data availability
Data are available on https://www.sharkipedia.org/ and at https://doi.org/10.5281/zenodo.4135325. Source data are provided with this paper.
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Acknowledgements
We thank all members of the IUCN SSC SSG and other experts who contributed to the data collation and, in particular, A. Aires-da-Silva, F. Carvalho, J. Cheok, S. Clarke, R. Coelho, E. Cortés, T. Driggers, C. Dudgeon, M. Hoffmann, Y. Jiao, T. Kashiwagi, A. Kock, C. Lowe, J. Rice, L. Tremblay-Boyer, W. J. VanderWright and S. Wintner. The scientific results and conclusions, as well as any views or opinions expressed herein, are those of the author(s) and do not necessarily reflect those of institutions or data providers. This project was funded by the Shark Conservation Fund, a philanthropic collaborative pooling expertise and resources to meet the threats facing the world’s sharks and rays. The Shark Conservation Fund is a project of Rockefeller Philanthropy Advisors. This work was funded by the Shark Conservation Fund as part of the Global Shark Trends Project to N.K.D. and C.A.S., and US National Science Foundation grant DEB-1556779 to H.K.K. P.M.K. was supported by the Marine Biodiversity Hub, a collaborative partnership supported through funding from the Australian Government’s National Environmental Science Program. N.K.D. was supported by Natural Science and Engineering Research Council Discovery and Accelerator Awards and the Canada Research Chairs Program.
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C.L.R., P.M.K., R.A.P. and N.K.D. organized and led the workshop investigation of data quality and facilitated the 2018 Red List assessments. N.P., H.K.K. and N.K.D. conceptualized the analysis. J.S.Y., C.L.R., H.K.K., R.B.S., N.P. and N.K.D. compiled and curated the time-series data. J.K.C., A.D.M. and H.W. provided additional time-series data. N.P., R.B.S. and H.W. conducted the statistical analysis. N.P., H.K.K. and N.K.D. visualized the data and wrote the first draft. N.K.D. and H.K.K. acquired the funding. All authors discussed the time-series data, analysis and results, and contributed to writing the manuscript.
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Extended data figures and tables
Extended Data Fig. 1 Hierarchical building of the global LPI and RLI.
LC, least concern; NT, near threatened; VU, vulnerable; EN, endangered; CR, critically endangered; EX, extinct.
Extended Data Fig. 2 Calculation of the LPI.
a, Schematic example of constructing the observed (black) and projected (blue) LPI. First, year-to-year rates of change (yyrc) (dt) are averaged between species in the same region (for example, in region 1 (R1), species A with \({d}_{{{\rm{A}}}_{t}}\) and species B with \({d}_{{{\rm{B}}}_{t}}\) averaged in \({d}_{{{\rm{R}}1}_{t}}\)). In a second step, yyrc are averaged between regions 1, 2 and 3 to give the global yyrc. The observed LPI builds on the yyrc calculated from the estimated abundance index from the state–space population model. The projected LPI builds on the yyrc calculated from the estimated and projected abundance index from the state-space population model. Projections are from the last data point to 2020. b, Global LPI for oceanic sharks and rays estimated from 1970 to 2018 in black and extrapolated to 2020 in blue. The black and the thick blue lines denote, respectively, the mean of the estimated and extrapolated LPI. The white and thin blues lines denote, respectively, the 95% credible intervals of the estimated and extrapolated LPI and the grey lines denote each iteration of the estimated LPI. c, The annual percentage change was calculated from the posteriors of the estimated LPI (grey) and extrapolated LPI (blue) around the final-assessment year relative to the posteriors for 1970. Vertical bars for the 1970–2018 period denote the median of the estimated and extrapolated LPI.
Extended Data Fig. 3 Global and species-specific LPI for oceanic sharks and rays from 1970 to 2018.
Global original LPI is the mean black line. Faint grey lines show the effect of excluding all data for a single species at a time and recalculating the mean global LPI for all other species. No means from jackknife species trends fall outside the 95% credible interval from the run with all of the datasets included, suggesting that our selection of species did not unduly influence the overall LPI result.
Extended Data Fig. 4 Time-series output for Carcharhinidae.
a–d, Observed (black or empty points and stars indicate different time-series) and modelled (black line) abundance indices for silky shark (Carcharhinus falciformis) (a), oceanic whitetip shark (C. longimanus) (b), dusky shark (C. obscurus) (c) and blue shark (Prionace glauca) (d) obtained from the state–space population model. The thick black line denotes the mean of the estimated abundance index and the shaded regions denote 95% credible intervals.
Extended Data Fig. 5 Time-series output for Sphyrnidae.
a–c, Observed (black or empty points and stars indicate different time-series) and modelled (black line) abundance indices for scalloped hammerhead (S. lewini) (a), great hammerhead (S. mokarran) (b) and smooth hammerhead (S. zygaena) (c) obtained from the state–space population model. The thick black line denotes the mean of the estimated abundance index and the shaded regions denote 95% credible intervals.
Extended Data Fig. 6 Time-series output for Alopiidae.
a–c, Observed (points) and modelled (black line) abundance indices for pelagic thresher (A. pelagicus) (a), bigeye thresher (Alopias superciliosus) (b) and common thresher (Alopias vulpinus) (c) obtained from the state–space population model. The thick black line denotes the mean of the estimated abundance index and the shaded regions denote 95% credible intervals.
Extended Data Fig. 7 Time-series output for Lamnidae.
a–d, Observed (black or empty points and stars indicate different time-series) and modelled (black line) abundance indices for white shark (C. carcharias) (a), shortfin mako (I. oxyrinchus) (b), longfin mako (I. paucus) (c) and porbeagle (L. nasus) (d) obtained from the state–space population model. The thick black line denotes the mean of the estimated abundance index and the shaded regions denote 95% credible intervals.
Extended Data Fig. 8 Time-series output for Dasyatidae and Mobulidae.
a–d, Observed (points) and modelled (black line) abundance indices for pelagic stingray (P. violacea) (a), reef manta ray (M. alfredi) (b), giant manta ray (Mobula birostris) (c) and shortfin devilray (M. kuhlii) (d) obtained from the state–space population model. The thick black line denotes the mean of the estimated abundance index and the shaded regions denote 95% credible intervals.
Extended Data Fig. 9 Stock assessments for oceanic sharks.
a, Oceanic shark stock status—over time—being at levels of biomass or abundance above MSY (green lines) or below MSY (red lines). Data were obtained from refs. 24,25,28,51, and refs. 81–84,93,94,96,97 in the Supplementary Information. Dotted lines indicate that a stock is above or below the biomass or abundance levels producing MSY following the last stock assessment value. b, Number of published stock assessments for oceanic sharks and rays over time. c, Presentation of 14 stocks of oceanic sharks (no available stock assessments for oceanic rays), status (biomass or abundance over value at MSY) versus pressure (F/FMSY) in a Kobe plot style, for the last year with available data. Circles represent the unique values of each species if only one stock exists and represent the mean of the values of the different stocks (diamonds) when the species has multiple stocks. The plot is divided into four panels: the red panel (top left), with four stocks and three species, corresponds to stocks that are being overfished and where overfishing is occurring; the orange panel (top right), with one stock and one species, corresponds to stocks that are not overfished but where overfishing is occurring; the yellow panel (bottom left), with four stocks and three species, corresponds to stocks that are overfished but where overfishing is not occurring; and the green panel (bottom right), with five stocks and one species, corresponds to stocks that are not overfished and where overfishing is not occurring.
Extended Data Fig. 10 Percentage of reported threat categories in the 31 oceanic shark IUCN Red List assessments.
‘Biological resource use’ and, more specifically, ‘fishing and harvesting aquatic resources’ is the major reported threat.
Supplementary information
Supplementary Information
This file contains Supplementary Methods 1 and 2, Supplementary Tables 1-3, Supplementary Discussion 1-3 and Supplementary References. The Supplementary Methods 1 explains the method used to correct fishing effort, using technological efficiency, into an effective fishing effort. The Supplementary Methods 2 describes the nine encountered situations details when selecting generation time of species and describes the quality of data. Supplementary Table 1 describes all the time-series analysed and provides the ecological information used in the analyses. Supplementary Table 2 describes all the available Red List status available for oceanic sharks and rays and the ones used in the analyses. Supplementary Table 3 describes the type of trajectories and gives the source of the 15 stock assessment outputs of 8 species used in the analysis. The Supplementary Discussion 2 discusses the reasons why the Living Planet Index analysis for oceanic sharks and rays is conservative (true abundance trend index values are likely to be lower and the calculated percent declines worse than estimated here). The Supplementary Discussion 2 discusses the declines in devil rays’ time-series in Mozambique and the context suggesting that these declines may have occurred in other Indian Ocean countries. The Supplementary Discussion 3 discusses some additional management details of the regional fishery management organizations focused on tunas, relative to oceanic shark species.
Supplementary Data 1
Table of the LPI per oceanic shark and ray species per year: median (Credible Interval 95%).
Supplementary Data 2
Table of compiled time-series of mean oceanic shark stock assessments biomass/abundance trajectories relative to maximum sustainable yield per year.
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Pacoureau, N., Rigby, C.L., Kyne, P.M. et al. Half a century of global decline in oceanic sharks and rays. Nature 589, 567–571 (2021). https://doi.org/10.1038/s41586-020-03173-9
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DOI: https://doi.org/10.1038/s41586-020-03173-9
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