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Small-scale gill-net fisheries cause massive green turtle Chelonia mydas mortality in Baja California Sur, Mexico

  • Agnese Mancini (a1), Volker Koch (a1), Jeffrey A. Seminoff (a2) and Bénédicte Madon (a3)
Abstract
Abstract

The coastal waters of Baja California Sur, Mexico, include some of the most important foraging grounds of the East Pacific green turtle Chelonia mydas. However, they are also important fishing grounds for artisanal fleets, leading potentially to high levels of bycatch mortality. We studied the impact of a small-scale gill-net fishery at San Ignacio lagoon, north-west Mexico, an important green turtle feeding ground. We conducted mortality censuses and interviewed local fishers to estimate total bycatch mortality at the lagoon. We also used marked drifters and carcasses to estimate stranding probabilities of turtles taken as bycatch. During 2006–2009 we found 262 dead turtles; 96% of the mortality occurred in May–August corresponding to the fishing season for halibut Paralichthys californicus and guitar-fish (Rhinobatus sp.). Stranding probability estimated from drifters was 0.062 (95% confidence interval, CI, 0.035–0.094), yielding a minimum mortality of 3,516 turtles during 2006–2008 (95% CI 2,364–6,057) or 1,172 animals per year. This is probably an underestimate of real mortality as the drifters have higher stranding probabilities than carcasses and most of the nets were set in the lower lagoon where carcasses rarely strand. Interviews with local fishers yielded a similar estimate of 1,087 (95% CI 901–1,286) dead turtles per year. This study is emblematic of the impact of artisanal fleets on marine turtles caused by overlap of fishing and turtle feeding areas. In 2009 strandings declined by > 97%, resulting from a change in fishing practices because of increased vigilance by enforcement authorities, underscoring the importance of law enforcement to protect threatened species.

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Corresponding author
Universidad Autónoma de Baja California Sur, Departamento de Biología Marina, Carretera al Sur km 5.5, 23080 La Paz, BCS, Mexico. E-mail vokoch@uabcs.mx
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L.B. Brooks , J.T. Harvey & W.J Nichols . (2009) Tidal movements of East Pacific green turtle Chelonia mydas at a foraging area in Baja California Sur, México. Marine Ecology Progress Series, 386, 263274.

L. Bugoni , L. Krause & M.V. Petry (2001) Marine debris and human impacts on sea turtles in southern Brazil. Marine Pollution Bulletin, 42, 13301334.

A. Carranza , A. Domingo & A. Estrades (2006) Pelagic longlines: a threat to sea turtles in the Equatorial Eastern Atlantic. Biological Conservation, 131, 5257.

C. Carreras , L. Cardona & A. Aguilar (2004) Incidental catch of the loggerhead turtle Caretta caretta off the Balearic Islands (western Mediterranean). Biological Conservation, 117, 321329.

P. Casale , M. Affronte , G. Isacco , D. Freggi , C. Vallini , P.P. d’Astore . (2010) Sea turtle strandings reveal high anthropogenic mortality in Italian waters. Aquatic Conservation: Marine and Freshwater Ecosystems, 20, 611620.

M. Chaloupka , T.M. Work , G.H. Balazs , S.K. Murakawa & R. Morris (2008) Cause-specific temporal and spatial trends in green sea turtles in the Hawaiian Archipelago (1982-2003). Marine Biology, 154, 887898.


E. Gilman , E. Zollett , S. Beverly , H. Nakano , K. Davis , D. Shiode . (2006) Reducing sea turtle by-catch in pelagic longline fisheries. Fish and Fisheries, 7, 223.

B.J. Godley , A.C. Gücü & A.C. Broderick (1998) Interaction between marine turtles and artisanal fisheries in the eastern Mediterranean: a probable cause for concern? Zoology in the Middle East, 16, 4984.

K.M. Hart , P. Mooreside & L.B. Crowder (2006) Interpreting the spatio-temporal patterns of sea turtle strandings: going with the flow. Biological Conservation, 129, 283290.

S.S. Heppell , H. Caswell & L.B. Crowder (2000) Life histories and elasticity patterns: perturbation analysis for species with minimal demographic data. Ecology, 81, 654665.

V. Koch , L.B. Brook & W.J. Nichols (2007) Population ecology of the green/black turtle (Chelonia mydas) in Bahía Magdalena, Mexico. Marine Biology, 153, 3546.

V. Koch , W.J. Nichols , H. Peckham & V. de la Toba (2006) Estimates of sea turtle mortality from poaching and bycatch in Bahía Magdalena, Baja California Sur, Mexico. Biological Conservation, 128, 327334.

R.L. Lewison & L.B. Crowder (2007) Putting longline bycatch of sea turtles into perspective. Conservation Biology, 21, 7986.

R.L. Lewison , L.B. Crowder , A.J. Read & S.A Freeman . (2004b) Understanding impacts of fisheries bycatch on marine megafauna. Trends in Ecology & Evolution, 19, 598604.

R.L. Lewison , L.B. Crowder & D.J. Shaver (2003) The impact of turtle excluder devices and fisheries closures on loggerhead and Kemp’s ridley strandings in the western Gulf of Mexico. Conservation Biology, 17, 10891097.

R.L. Lewison , S.A. Freeman & L.B. Crowder (2004a) Quantifying the effects of fisheries on threatened species: the impact of pelagic longlines on loggerhead and leatherback sea turtles. Ecology Letters, 7, 221231.

M.C. López-Castro , V. Koch , A. Mariscal-Loza & W.J. Nichols (2010) Long-term monitoring of black turtles Chelonia mydas at coastal foraging areas off the Baja California Peninsula. Endangered Species Research, 11, 3545.

A. Mancini & V. Koch (2009) Sea turtle consumption and black market trade in Baja California Sur, Mexico. Endangered Species Research, 7, 110.

J.F. Muhlin , C.R. Engel , R. Stessel , R.A. Weatherbee & S.H. Brawley (2008) The influence of coastal topography, circulation patterns, and rafting in structuring populations of an intertidal alga. Molecular Ecology, 17, 11981210.

S.H. Peckham , D.M. Diaz , A. Walli , G. Ruiz , L.B. Crowder & W.J. Nichols (2007) Small-scale fisheries bycatch jeopardizes endangered pacific loggerhead turtles. PLoS ONE, 2(10), e1041.

S.H. Peckham , D. Maldonado-Diaz , V. Koch , A. Mancini , A. Gaos , M.T. Tinker & W.J. Nichols (2008) High mortality of loggerhead turtles due to bycatch, human consumption and strandings at Baja California Sur, Mexico, 2003 to 2007. Endangered Species Research, 5, 171183.

J. Quiñones , V. Gonzalez Carmen , J. Zeballos , S. Purca & H. Manzan (2010) Effects of El Niño-driven environmental variability on black turtle migration to Peruvian foraging grounds. Hydrobiologia, 645, 6979.

C.R. Sasso & S.P. Epperly (2006) Seasonal sea turtle mortality risk from forced submergence in bottom trawls. Fisheries Research, 81, 8688.


J.A. Seminoff , A. Resendiz & W.J. Nichols (2002) Home range of the East Pacific green turtle, Chelonia mydas at a coastal foraging ground in the Gulf of California, Mexico. Marine Ecology Progress Series, 242, 253265.

J. Senko , V. Koch , W. Megill , R.M. Carthy , R. Templeton & W.J. Nichols (2010a) Fine-scale daily movement patterns and habitat use of an endangered marine megaherbivore at a shallow coastal lagoon. Journal of Experimental Marine Biology and Ecology, 391, 92100.

J. Senko , M. Lopez-Castro , V. Koch & W.J. Nichols (2010b) Immature East Pacific green turtles (Chelonia mydas) use multiple foraging areas off the Pacific Coast of Baja California Sur, Mexico: first evidence from mark-recapture data. Pacific Science, 64, 125130.

K. Shanker , B. Pandav & B.C. Choudhury (2004) An assessment of the olive ridley turtle nesting population in Orissa, India. Biological Conservation, 115, 149160.

C.U. Soykan , J.E. Moore , R. Zydelis , L.B. Crowder , C. Safina & R.L. Lewison (2008) Why study bycatch? An introduction to the Theme Section on fisheries bycatch. Endangered Species Research, 5, 91102.

J. Tomás , P. Gozalbes , J.A. Raga & B.J. Godley (2008) Bycatch of loggerhead sea turtles: insights from 14 years of stranding data. Endangered Species Research, 5, 167169.

B.J. Worton (1989) Kernel methods for estimating the utilization distribution in home-range studies. Ecology, 70, 164168.

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Oryx
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