Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Comprehensive bycatch assessment in US fisheries for prioritizing management


Wild-capture fisheries help provide food security to billions of people, yet bycatch of non-target species threatens ecosystem health and fishery sustainability. Appropriate monitoring and fisheries management can mitigate bycatch but require standardized bycatch data to be robustly recorded and effectively disseminated. Here we integrated and analysed 30,473 species-specific bycatch records from 95 US fisheries in 2010–2015. We examined patterns in fish and invertebrate, marine mammal, seabird and sea turtle bycatch and developed a standardized scoring system, the relative bycatch index, to assess bycatch performance of each fishery. The estimated amount of fish and invertebrate discards totalled 1.93 million tonnes (4.26 billion pounds) over the 6-year period. We found that the national discard rate is 10.5%, considerably lower than past estimates. Results from our relative bycatch index analysis can be used to facilitate management intervention strategies for particular fisheries or gear types, such as shrimp and otter trawls and several pelagic longline and gillnet fisheries, which had the poorest bycatch performance. These findings underscore the need for continued, high-quality, easily accessible bycatch information to better support fisheries management in the United States and globally.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Prices vary by article type



Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Proportion of US federally managed fisheries appearing in the NBR sorted by gear type in five NMFS reporting regions.
Fig. 2: Bycatch patterns in all fisheries.
Fig. 3: Distribution of relative bycatch index (RBI) scores.
Fig. 4: The annual relative bycatch index (RBI) score for 61 fisheries that have 6 years of data (2010–2015).

Data availability

All the raw NBR data can be explored, queried, visualized and downloaded at:

Code availability

All code used to analyse data and generate plots found in the paper is at:


  1. Food and Agriculture Organization. The State of World Fisheries and Aquaculture 2018 – Meeting the Sustainable Development Goals (FAO, 2018).

  2. Benaka, L. R., Bullock, D., Hoover, A. L. & Olsen, N. A. (eds) US National Bycatch Report First Edition Update 3 (US Department of Commerce, NOAA, 2019).

  3. Davies, R. W. D., Cripps, S. J., Nickson, A. & Porter, G. Defining and estimating global marine fisheries bycatch. Mar. Policy 33, 661–672 (2009).

    Article  Google Scholar 

  4. Pérez-Roda, M. et al. A Third Assessment of Global Marine Fisheries Discards No. 633 (FAO, 2019).

  5. Gilman, E. L. Bycatch governance and best practice mitigation technology in global tuna fisheries. Mar. Policy 35, 590–609 (2011).

    Article  Google Scholar 

  6. Gilman, E. et al. Robbing Peter to pay Paul: replacing unintended cross-taxa conflicts with intentional tradeoffs by moving from piecemeal to integrated fisheries bycatch management. Rev. Fish. Biol. Fish. 29, 93–123 (2019).

    Article  Google Scholar 

  7. Wilcox, C. & Donlon, C. D. Compensatory mitigation as a solution to fisheries bycatch–biodiversity conservation conflicts. Front. Ecol. Environ. 5, 325–331 (2007).

    Article  Google Scholar 

  8. Lewison, R. L., Crowder, L. B., Read, A. J. & Freeman, S. A. Understanding impacts of fisheries bycatch on marine megafauna. Trends Ecol. Evol. 19, 598–604 (2004).

    Article  Google Scholar 

  9. Lewison, R. L. et al. Global patterns of marine mammal, seabird, and sea turtle bycatch reveal taxa-specific and cumulative megafauna hotspots. Proc. Natl Acad. Sci. USA 111, 5271–5276 (2014).

    Article  CAS  Google Scholar 

  10. Little, A. S., Needle, C. L., Hilborn, R., Holland, D. S. & Marshall, C. T. Real-time spatial management approaches to reduce bycatch and discards: experiences from Europe and the United States. Fish. Fish. 16, 576–602 (2015).

    Article  Google Scholar 

  11. Senko, J., White, E. R., Heppell, S. S. & Gerber, L. R. Comparing bycatch mitigation strategies for vulnerable marine megafauna. Anim. Conserv. 17, 5–18 (2014).

    Article  Google Scholar 

  12. Eguchi, T., Benson, S. R., Foley, D. G. & Forney, K. A. Predicting overlap between drift gillnet fishing and leatherback turtle habitat in the California current ecosystem. Fish. Oceanogr. 26, 17–33 (2017).

    Article  Google Scholar 

  13. Swimmer, Y. et al. Food color and marine turtle feeding behavior: can blue bait reduce turtle bycatch in commercial fisheries? Mar. Ecol. Prog. Ser. 295, 273–278 (2005).

    Article  Google Scholar 

  14. Shiode, D., Hu, F., Shiga, M., Yokota, K. & Tokai, T. Midwater float system for standardizing hook depths on tuna longlines to reduce sea turtle by-catch. Fish. Sci. 71, 1182–1184 (2005).

    Article  CAS  Google Scholar 

  15. Pierre, J. P. & Norden, W. S. Reducing seabird bycatch in longline fisheries using a natural olfactory deterrent. Biol. Conserv. 130, 406–415 (2006).

    Article  Google Scholar 

  16. Swimmer, Y. et al. Sea turtle bycatch mitigation in US longline fisheries. Front. Mar. Sci. 4, 260 (2017).

    Article  Google Scholar 

  17. Melvin, E. F., Guy, T. J. & Read, L. B. Best practice seabird bycatch mitigation for pelagic longline fisheries targeting tuna and related species. Fish. Res. 149, 5–18 (2014).

    Article  Google Scholar 

  18. Alessandro, L. & Antonello, S. An overview of loggerhead sea turtle (Caretta caretta) bycatch and technical mitigation measures in the Mediterranean Sea. Rev. Fish. Biol. Fish. 20, 141–161 (2010).

    Article  Google Scholar 

  19. Barlow, J. & Cameron, G. A. Field experiments show that acoustic pingers reduce marine mammal bycatch in the California drift gill net fishery. Mar. Mammal. Sci. 19, 265–283 (2003).

    Article  Google Scholar 

  20. Carretta, J. V., Barlow, J. & Enriquez, L. Acoustic pingers eliminate beaked whale bycatch in a gill net fishery. Mar. Mammal. Sci. 24, 956–961 (2008).

    Google Scholar 

  21. Hobday, A. J., Hartog, J. R., Spillman, C. M. & Alves, O. Seasonal forecasting of tuna habitat for dynamic spatial management. Can. J. Fish. Aquat. Sci. 68, 898–911 (2011).

    Article  Google Scholar 

  22. Turner, S. M. et al. Cooperative research to evaluate an incidental catch distribution forecast. Front. Mar. Sci. 4, 116 (2017).

    Article  Google Scholar 

  23. Hazen, E. L. et al. A dynamic ocean management tool to reduce bycatch and support sustainable fisheries. Sci. Adv. 4, eaar3001 (2018).

    Article  Google Scholar 

  24. Gilman, E., Passfield, K. & Nakamura, K. Performance of regional fisheries management organizations: ecosystem-based governance of bycatch and discards. Fish. Fish. 15, 327–351 (2014).

    Article  Google Scholar 

  25. Halpern, B. S. et al. Spatial and temporal changes in cumulative human impacts on the world’s ocean. Nat. Commun. 6, 7615 (2015).

    Article  CAS  Google Scholar 

  26. Di Minin, E. et al. Identifying global centers of unsustainable commercial harvesting of species. Sci. Adv. 5, eaau2879 (2019).

    Article  Google Scholar 

  27. Harrington, J. M., Myers, R. A. & Rosenberg, A. A. Wasted Resources: Bycatch and discards in US Fisheries (Oceana, 2005).

  28. Brooke, S. G., Desfosse, L. L. & Karp, W. A. Estimating overall fish bycatch in US commercial fisheries. Mar. Fish. Rev. 74, 1–5 (2012).

    Google Scholar 

  29. NOAA/NMFS. Fishery stock status updates. NOAA Fisheries (2019).

  30. Dulvy, N. K. et al. Extinction risk and conservation of the world’s sharks and rays. eLife 3, e00590 (2014).

    Article  Google Scholar 

  31. Cassoff, R. M. et al. Lethal entanglement in baleen whales. Dis. Aquat. Organ 96, 175–185 (2011).

    Article  Google Scholar 

  32. Wallace, B. P. et al. Global patterns of marine turtle bycatch. Conserv. Lett. 3, 131–142 (2010).

    Article  Google Scholar 

  33. Stock Assessment and Fishery Evaluation (SAFE) Report for Atlantic Highly Migratory Species (NOAA/NMFS, 2019).

  34. Wallace, B. P., Heppell, S. S., Lewison, R. L., Kelez, S. & Crowder, L. B. Impacts of fisheries bycatch on loggerhead turtles worldwide inferred from reproductive value analyses. J. Appl. Ecol. 45, 1076–1085 (2008).

    Google Scholar 

  35. Bolten, A. B. et al. Quantifying multiple threats to endangered species: an example from loggerhead sea turtles. Front. Ecol. Environ. 9, 295–301 (2011).

    Article  Google Scholar 

  36. Casale, P. & Heppell, S. S. How much sea turtle bycatch is too much? A stationary age distribution model for simulating population abundance and potential biological removal in the Mediterranean. Endanger. Species Res. 29, 239–254 (2016).

    Article  Google Scholar 

  37. Melvin, E. F., Dietrich, K. S., Suryan, R. M. & Fitzgerald, S. M. Lessons from seabird conservation in Alaskan longline fisheries. Conserv. Biol. 33, 842–852 (2019).

    Article  Google Scholar 

  38. Read, A. J., Drinker, P. & Northridge, S. Bycatch of marine mammals in US and global fisheries. Conserv. Biol. 20, 163–169 (2006).

    Article  Google Scholar 

  39. McDonald, S. L., Lewison, R. L. & Read, A. J. Evaluating the efficacy of environmental legislation: a case study from the US marine mammal take reduction planning process. Glob. Ecol. Conserv. 5, 1–11 (2016).

    Article  Google Scholar 

  40. Hayes, S. A., Gardner, S., Garrison, L., Henry, A. & Leandro, L. North Atlantic Right Whales – Evaluating Their Recovery Challenges in 2018 (NOAA, 2018).

  41. Lebon, K. M. & Kelly, R. P. Evaluating alternatives to reduce whale entanglements in commercial Dungeness crab fishing gear. Glob. Ecol. Conserv. 18, e00608 (2019).

    Article  Google Scholar 

  42. Costello, C. et al. Global fishery prospects under contrasting management regimes. Proc. Natl Acad. Sci. USA 113, 5125–5129 (2016).

    Article  CAS  Google Scholar 

  43. North Pacific Fishery Management Council Pollock Conservation Cooperative and High Seas Catchers’ Cooperative Joint Annual Report 2018 (NPFMC, 2019).

  44. Lewison, R. et al. Dynamic ocean management: identifying the critical ingredients of dynamic approaches to ocean resource management. Bioscience 65, 486–498 (2015).

    Article  Google Scholar 

  45. National Oceanic and Atmospheric Administration. Fish and fish product import provisions of the Marine Mammal Protection Act. Fed. Register 81, 1–31 (2016).

    Google Scholar 

  46. Rausser, G., Hamilton, S., Kovach, M. & Stifter, R. Unintended consequences: the spillover effects of common property regulations. Mar. Policy 33, 24–39 (2009).

    Article  Google Scholar 

  47. Zeller, D., Cashion, T., Palomares, M. & Pauly, D. Global marine fisheries discards: a synthesis of reconstructed data. Fish. Fish. 19, 30–39 (2018).

    Article  Google Scholar 

  48. Burgess, M. G., Polasky, S. & Tilman, D. Predicting overfishing and extinction threats in multispecies fisheries. Proc. Natl Acad. Sci. USA 110, 15943–15948 (2013).

    Article  CAS  Google Scholar 

  49. Burgess, M. G. et al. Protecting marine mammals, turtles, and birds by rebuilding global fisheries. Science 359, 1255–1258 (2018).

    Article  CAS  Google Scholar 

  50. Howell, E. A., Kobayashi, D. R., Parker, D. M., Balazs, G. H. & Polovina, J. J. TurtleWatch: a tool to aid in the bycatch reduction of loggerhead turtles Caretta caretta in the Hawaii-based pelagic longline fishery. Endanger. Species Res. 5, 267–278 (2008).

    Article  Google Scholar 

  51. Wickham, H. Tidy data. J. Stat. Softw. 59, 1–23 (2014).

    Article  Google Scholar 

  52. Evaluating Bycatch: A National Approach to Standardized Bycatch Monitoring Programs (NOAA/NMFS, 2004).

  53. Desfosse, L. L., Karp, W. A. & Brooke, S. G. Evaluating the quality of bycatch data and bycatch estimates among disparate fisheries. Mar. Fish. Rev. 74, 6–13 (2012).

    Google Scholar 

  54. Vanderwal, J., Falconi, L., Januchowski, S., Shoo, L. & Storlie, C. SDMTools. Species distribution modelling tools: tools for processing data associated with species distribution modelling exercises (CRAN, 2014);

  55. Brodie, S. et al. Improving consumption rate estimates by incorporating wild activity into a bioenergetics model. Ecol. Evol. 6, 2262–2274 (2016).

    Article  Google Scholar 

  56. Murphy, W. & Rowlingson, B. Fiftystater: map data to visualize the fifty US states with Alaska and Hawaii insets (CRAN, 2016);

Download references


We thank the fisheries observers who collected bycatch data that informed this work. Further, we thank the team at the National Observer Program (NOAA/NMFS) for drafting the NBRs, which provided the raw data used in this study. In addition, we appreciate data management assistance by C. Donegan and an internal review by S. Mesnick and J. Carretta (NOAA Southwest Fisheries Science Center). This work was made possible by a California Sea Grant Fellowship to M.S.S. and funding through the Fisheries Information Systems NOAA/NMFS.

Author information

Authors and Affiliations



M.S.S., L.R.B., S.J.B. and E.L.H. conceived and designed the study. M.S.S., S.B., H.W. and A.H. analysed the data. H.W. created the web application with input from all authors. M.S.S. wrote the manuscript with input and edits from all authors.

Corresponding author

Correspondence to Matthew S. Savoca.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–4 and text.

Reporting Summary

Rights and permissions

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Savoca, M.S., Brodie, S., Welch, H. et al. Comprehensive bycatch assessment in US fisheries for prioritizing management. Nat Sustain 3, 472–480 (2020).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing