Marine Biology

, Volume 160, Issue 3, pp 653–665 | Cite as

Identifying and mapping local bycatch hotspots of loggerhead sea turtles using a GIS-based method: implications for conservation

  • Giulia CambièEmail author
  • Noela Sánchez-Carnero
  • Toni Mingozzi
  • Ramón Muiño
  • Juan Freire
Original Paper


Fisheries bycatch of marine megafauna is a worldwide conservation issue. In this study, we propose a method for generating reliable maps of sea turtle bycatch hotspots. Based on a well-defined area of fishing effort determined from the longline sets monitored in 2007 and 2010, we calculated the fishing area with the highest turtle bycatch density for both years. Our results show that it is important to consider all the components of fishing effort (area, number of hooks and soak time) in order to standardize the bycatch events, and thus the spatial density of the captures can be considered an index of abundance and aggregation of the species. Moreover, the high-resolution level of the analyses was useful for investigating the cumulative effect of the longline sets, which often overlap, and made it possible to correctly map the capture density and the intensity of the fishing effort at any given location.


Fishing Advanced Very High Resolution Radiometer Advanced Very High Resolution Radiometer Fishing Effort Longline Fishery 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



The authors would like to thank all the fishers involved in the survey for their assistance and unconditional support of this project. A special thanks to P. and C. Polimeno, S. Urso, S. Aceña, and V. Urgorri for the valuable help. We are also indebted to E Raabe of Arc Dehooker for providing the “Turtle Kits” for free and to Spanish Centro de Recepción, Proceso, Archivo y Distribución de Imágenes de Observación de la Tierra (CREPAD) for processing images. Finally, we wish to thank two anonymous reviewers for their very useful comments and suggestions.


  1. Báez JC, Real R, Garcia-Soto C, de la Serna JM, Macias D, Camiñas JA (2007) Loggerhead turtle by-catch depends on distance to the coast, independent of fishing effort: implications for conservation and fisheries management. Mar Ecol Prog Ser 338:249–256CrossRefGoogle Scholar
  2. Baum JK, Myers RA, Kehler DG, Worm B, Harley SJ, Doherty PA (2003) Collapse and conservation of shark populations in the Northwest Atlantic. Science 299:389–392CrossRefGoogle Scholar
  3. Beets J, Friedlander A (1999) Evaluation of a conservation strategy: a spawning aggregation closure for red hind, Epinephelus guttatus, in the U.S. Virgin Islands. Environ Biol Fish 55:91–98CrossRefGoogle Scholar
  4. Braun-McNeill J, Sasso CR, Epperly SP, Rivero C (2008) Feasibility of using sea surface temperature imagery to mitigate cheloniid sea turtle–fishery interactions off the coast of northeastern USA. Endang Species Res 5:257–266CrossRefGoogle Scholar
  5. Cambiè G (2011) Incidental capture of Caretta caretta in trammel nets off the western coast of Sardinia (Italy): statistical models of capture abundance and immediate survival. Aquat Conserv Mar Freshw Ecosyst 21:28–36CrossRefGoogle Scholar
  6. Cambiè G, Camiñas JA, Franquesa R, Mingozzi T (2010) Fishing activity and impacts along the main nesting area of loggerhead sea turtle Caretta caretta in Italy: overwhelming discrepancy with the official data. Sci Mar 74:275–285CrossRefGoogle Scholar
  7. Cambiè G, Muiño R, Freire J, Mingozzi T (2012) Effects of small (13/0) circle hooks on loggerhead sea turtle bycatch in a small-scale, Italian pelagic longline fishery. Bull Mar Sci 88:719–730CrossRefGoogle Scholar
  8. Campbell RA (2004) CPUE standardisation and the construction of indices of stock abundance in a spatially varying fishery using general linear models. Fish Res 70:209–227CrossRefGoogle Scholar
  9. Casale P (2011) Sea turtle by-catch in the Mediterranean. Fish Fish 12:299–316CrossRefGoogle Scholar
  10. Casale P, Affronte M, Insacco G, Freggi D, Vallini C, Pino d’Astore P, Basso R, Paolillo G, Abbate G, Argano R (2010) Sea turtle strandings reveal high anthropogenic mortality in Italian waters. Aquat Conserv Mar Freshw Ecosyst 20:611–620CrossRefGoogle Scholar
  11. Chaloupka M (2007) Using Bayesian belief networks to evaluate the relative risk of fishing gear types on sea turtle stocks. FAO. Report of the workshop on assessing the relative importance of sea turtle mortality due to fisheries in Southeast Asia, Bangkok, 19–23 March 2007. FAO interactions between sea turtles and fisheries within an ecosystem context meeting report 2. Food and Agriculture Organization of the United Nations and SEAFDEC, Rome and Bangkok, pp 129–140Google Scholar
  12. COM (2011) Proposal for a regulation of the European Parliament and of the Council on the Common Fisheries Policy. COM, Brussels.
  13. Cressie N, Stern HS, Wright DR (2000) Mapping rates associated with polygons. J Geograph Syst 2:61–69CrossRefGoogle Scholar
  14. D’Agrosa CE (2004) The application of spatial analytical techniques toward the conservation of long-lived marine vertebrates: the pelagic longline fishery as a case study. Dissertation, Duke University, Durham, North Carolina, USAGoogle Scholar
  15. Davoren GK (2007) Effects of gill-net fishing on marine birds in a biological hotspot in the Northwest Atlantic. Cons Biol 21:1032–1045CrossRefGoogle Scholar
  16. Diamond SL (2004) Bycatch quotas in the Gulf of Mexico shrimp trawl fishery: can they work? Rev Fish Biol Fish 14:207–237CrossRefGoogle Scholar
  17. Dunn DC, Kot CY, Halpin PN (2008) A comparison of methods to spatially represent pelagic longline fishing effort in catch and bycatch studies. Fish Res 92:268–276CrossRefGoogle Scholar
  18. Dunn DC, Boustany AM, Halpin PN (2011) Spatio-temporal management of fisheries to reduce by-catch and increase fishing selectivity. Fish Fish 12:110–119CrossRefGoogle Scholar
  19. FAO Fisheries and Aquaculture Department (2009) Guidelines to reduce sea turtle mortality in fishing operations. Rome, FAO, p 128Google Scholar
  20. Fortin MJ, Dale MRT (2005) Spatial analysis: a guide for ecologists. Cambridge University Press, CambridgeGoogle Scholar
  21. Gardner B, Sullivan PJ, Morreale SJ, Epperly SP (2008) Spatial and temporal statistical analysis of bycatch data: patterns of sea turtle bycatch in the North Atlantic. Can J Fish Aquat Sci 65:2461–2470CrossRefGoogle Scholar
  22. Gilman EL (2011) Bycatch governance and best practice mitigation technology in global tuna fisheries. Mar Policy 35:590–609CrossRefGoogle Scholar
  23. Gilman EL, Dalzell P, Martin S (2006) Fleet communication to abate fisheries bycatch. Mar Policy 30:360–366CrossRefGoogle Scholar
  24. Goodyear CP (1999) An analysis of the possible utility of time–area closures to minimize billfish bycatch by U.S. pelagic longlines. Fish Bull 97:243–255Google Scholar
  25. Grantham HS, Petersen SL, Possingham HP (2008) Reducing bycatch in the South African pelagic longline fishery: the utility of different approaches to fisheries closures. Endang Species Res 5:291–299CrossRefGoogle Scholar
  26. Hall SJ, Mainprize BM (2005) Managing by-catch and discards: how much progress are we making and how can we do better? Fish Fish 6:134–155CrossRefGoogle Scholar
  27. IUCN (2011) IUCN red list of threatened species. Version 2011.2. Accessed on 20 Feb 2012
  28. Jentoft S (1989) Fisheries co-management: delegating government responsibility to fishermen’s organizations. Mar Policy 13:137–154CrossRefGoogle Scholar
  29. Kelleher K (2005) Discards in the world’s marine fisheries: an update. FAO Fish Tech Pap 470:131Google Scholar
  30. Kobayashi DR, Cheng I-J, Parker DM, Polovina JJ, Kamezaki N, Balazs GH (2011) Loggerhead turtle (Caretta caretta) movement off the coast of Taiwan: characterization of a hotspot in the East China Sea and investigation of mesoscale eddies. ICES J Mar Sci 68:707–718CrossRefGoogle Scholar
  31. Leeney RH, Amies R, Broderick AC, Witt MJ, Loveridge J, Doyle J, Godley BJ (2008) Spatio-temporal analysis of cetacean strandings and bycatch in a UK Wsheries hotspot. Biodiversity Conserv 17:2323–2338CrossRefGoogle Scholar
  32. Lewison RL, Soykan CU, Franklin J (2009) Mapping the bycatch seascape: multispecies and multi-scale spatial patterns of fisheries bycatch. Ecol Appl 19:920–930CrossRefGoogle Scholar
  33. Lutchman I, Grieve C, Des Clers S, De Santo E (2009) Towards a reform of the Common Fisheries Policy in 2012—a CFP health check. IEEP, London, p 80Google Scholar
  34. Maunder MN, Punt AE (2004) Standardizing catch and effort data: a review of recent approaches. Fish Res 70:141–159CrossRefGoogle Scholar
  35. Mingozzi T, Masciari G, Paolillo G, Pisani B, Russo M, Massolo A (2007) Discovery of a regular nesting area of loggerhead turtle Caretta caretta in southern Italy: a new perspective for national conservation. Biodiversity Conserv 16:3519–3541CrossRefGoogle Scholar
  36. Nelson TA, Boots B (2008) Detecting spatial hot spots in landscape ecology. Ecography 31:556–566CrossRefGoogle Scholar
  37. Polovina JJ, Kobayashi DR, Ellis DM, Seki MP, Balazs GH (2000) Turtles on the edge: movement of loggerhead turtles (Caretta caretta) along oceanic fronts in the central North Pacific, 1997–1998. Fish Oceanogr 9:71–82CrossRefGoogle Scholar
  38. Polovina J, Uchida I, Balazs G, Howell EA, Parker D, Dutton P (2006) The Kuroshio extension bifurcation region: a pelagic hotspot for juvenile loggerhead sea turtles. Deep Sea Res Part II 53:326–339CrossRefGoogle Scholar
  39. Rice PH, Goodyear CP, Prince ED, Snodgrass D, Serafy JE (2007) Use of catenary geometry to estimate hook depth during near-surface pelagic longline fishing: theory versus practice. N Am J Fish Manag 27:1148–1161CrossRefGoogle Scholar
  40. Sims M, Cox T, Lewison R (2008) Modeling spatial patterns in fisheries bycatch: improving bycatch maps to aid fisheries management. Ecol Appl 18:649–661CrossRefGoogle Scholar
  41. Spotila JR, Reina RR, Steyermark AC, Plotkin PT, Paladino FV (2000) Pacific leatherback turtles face extinction. Nature 405:529–530CrossRefGoogle Scholar
  42. Wallace BP, DiMatteo AD, Hurley BJ, Finkbeiner EM, Bolten AB et al (2010) Regional management units for marine turtles: a novel framework for prioritizing conservation and research across multiple scales. PLoS One 5(12):e15465. doi: 10.1371/journal.pone.0015465 CrossRefGoogle Scholar
  43. Watson J, Epperly S, Foster D, Shah A (2005) Fishing methods to reduce sea turtle mortality associated with pelagic longlines. Can J Fish Aquat Sci 62:965–981CrossRefGoogle Scholar
  44. Webster R, Oliver MA (2007) Characterizing spatial processes: the covariance and variogram. In: Geostatistics for Environmental Scientists, 2nd edn. Wiley, Chichester, pp 47–73Google Scholar
  45. Worm B, Lotze HK, Myers RA (2003) Predator diversity hotspots in the blue ocean. PNAS 100:9884–9888CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • Giulia Cambiè
    • 1
    • 2
    Email author
  • Noela Sánchez-Carnero
    • 3
  • Toni Mingozzi
    • 4
  • Ramón Muiño
    • 3
  • Juan Freire
    • 5
  1. 1.School of Ocean SciencesBangor UniversityMenai Bridge, AngleseyUK
  2. 2.Departamento de Zoología y Antropología FísicaUniversidad de Santiago de CompostelaSantiago de CompostelaSpain
  3. 3.Grupo de Recursos Marinos y Pesquerías, Facultad de CienciasUniversidade da CoruñaA CoruñaSpain
  4. 4.Dipartimento di EcologiaUniversità della CalabriaRendeItaly
  5. 5.Barrabés NextMadridSpain

Personalised recommendations