Abstract
Previous studies of loggerhead sea turtles have concluded that drifting longlines were the main threat for immature specimens in the western Mediterranean, because immature loggerhead sea turtles mainly inhabit oceanic waters. However, recent aerial surveys have revealed large numbers of immature loggerhead sea turtles over the continental shelf of eastern mainland Spain, where turtles are exposed to neritic fishing gears but not to drifting longlines. We satellite-tracked seven loggerhead sea turtles (minimum straight carapace length (SCLmin) range: 36.5–55.0 cm) to assess whether the turtles in this region are vagrants from the adjoining oceanic regions or whether these loggerheads mostly inhabit the continental shelf. Satellite-tracking revealed that six of the tagged turtles avoided the oceanic realm and made extended use of the continental shelf, whereas only one individual could be considered a true vagrant as it avoided the continental shelf and primarily used the oceanic habitat. These results are in sharp contrast with those previously reported for immature loggerhead sea turtles of similar size from the south-western Mediterranean and fit well a relaxed ontogenic model that was recently proposed for loggerhead sea turtles in the central Mediterranean. Furthermore, these results demonstrate the vulnerability of loggerhead sea turtles of eastern mainland Spain to neritic fishing gears, as three of the seven turtles died and one was bycaught incidentally while being tracked over the continental shelf.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Aguilar R, Mas J, Pastor X (1995) Impact of the Spanish swordfish longline fisheries on the loggerhead sea turtle Caretta caretta population in the western Mediterranean. In: Richardson JI, Richardson TH (eds) Proceedings of the 12th Annual Workshop on Sea Turtle biology and Conservation. NOAA Tech Memo NMFS-SEFSC-361, pp 1–6
Argos (2000) User’s manual. CLS, Ramonville
Avens L, Braun-McNeill J, Epperly S, Lohmann KJ (2003) Site fidelity and homing behavior in juvenile loggerhead sea turtles (Caretta caretta). Mar Biol 143:211–220
Báez JC, Real R, García-Soto C, de la Serna JM, Macías 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 338:249–256
Balazs G, Miya R, Beavers S (1996) Procedures to attach a satellite transmitter to the carapace of an adult green turtle, Chelonia mydas. In: Keinath J, Barnard D, Musick J, Bell B (eds) Proceedings of the Fifteenth Annual Symposium on Sea Turtle Biology and Conservation. NOAA Tech Memo NMFS-SEFSC-367, pp 21–26
Bentivegna F (2002) Intra-mediterranean migration of loggerhead sea turtles monitored by satellite telemetry. Mar Biol 141:795–800
Bertolero A (2003) Varamientos y capturas de tortugas marinas en los alrededores del Delta del Ebro (NE España) entre los años 1984 y 2001. Rev Esp Herpetol 17:39–54
Bolten AB (2000) Técnicas para la medición de tortugas marinas. In: Eckert KL, Bjorndal KA, Abreu-Grobois FA, Donnelly M (eds) Técnicas de investigación y manejo para la conservación de las tortugas marinas, Grupo Especialista en Tortugas Marinas UICN/CSE Publication No 4, pp 126–131
Broderick AC, Coyne MS, Fuller WJ, Glen F, Godley BJ (2007) Fidelity and over-wintering of sea turtles. Proc R Soc B 274:1533–1538
Camiñas JA, de la Serna JM (1995) The loggerhead distribution in the Western Mediterranean Sea as deduced from captures by the Spanish long line fishery. In: Llorente G, Montori A, Santos X, Carretero MA (eds) Scientia Herpetológica. Asociación Herpetológica Española, Barcelona, pp 316–323
Camiñas JA, Báez JC, Valeiras Z, Real R (2006) Differential loggerhead by-catch and direct mortality due to surface longlines according to boat strata and gear type. Sci Mar 70:661–665
Cardona L, Revelles M, Carreras C, San Félix M, Gazo M, Aguilar A (2005) Western Mediterranean immature loggerhead turtles: habitat use in spring and summer assessed through satellite tracking and aerial surveys. Mar Biol 147:583–591
Carreras C, Cardona L, Aguilar A (2004) Incidental catch of loggerhead turtles Caretta caretta off the Balearic Islands (western Mediterranean). Biol Conserv 117:321–329
Carreras C, Pont S, Maffucci F, Pascual M, Barceló A, Bentivegna F, Cardona L, Alegre F, SanFélix M, Fernández G, Aguilar A (2006) Genetic structuring of immature loggerhead sea turtles (Caretta caretta) in the Mediterranean Sea reflects water circulation patterns. Mar Biol 149:1269–1279
Casale P, Laurent L, De Metrio G (2004) Incidental capture of marine turtles by the Italian trawl fishery in the north Adriatic Sea. Biol Conserv 119:287–295
Casale P, Freggi D, Basso R, Vallini C, Argano R (2007) A model of area fidelity, nomadism, and distribution patterns of loggerhead sea turtles (Caretta caretta) in the Mediterranean Sea. Mar Biol 152:1039–1049
Casale P, Abbate G, Freggi D, Conte N, Oliverio M, Argano R (2008) Foraging ecology of loggerhead sea turtles Caretta caretta in the central Mediterranean Sea: evidence for a relaxed life history model. Mar Ecol Prog Ser 372:265–276
Crowder LB (1990) Community ecology. In: Schreck CB, Moyle PB (eds) Methods for fish biology. American Fisheries Society, Bethesda, pp 609–632
Deflorio M, Aprea A, Corriero A, Santamaría N, De Metrio G (2005) Incidental captures of sea turtles by swordfish and albacore longlines in the Ionina sea. Fish Sci 71:1010–1018
Dugger KM, Ballard G, Ainley DG, Barton KJ (2006) Effects of flipper bands on foraging behavior and survival of Adelie penguins (Pygoscelis adeliae). Auk 123:858–869
Eckert S, Moore JE, Dunn DC, Sagarminaga van Buiten R, Eckert KL, Halpin PN (2008) Modeling loggerhead turtle movement in the Mediterranean: importance of body size and oceanography. Ecol Appl 18:290–308
Estrada M (1996) Primary production in the northwestern Mediterranean. Sci Mar 60(suppl 2):55–64
Gauthier-Clerc M, Gendner JP, Ribic CA, Fraser WR, Woehler EJ, Descamps S, Gilly C, Le Bohec C, Le Maho Y (2004) Long-term effects of flipper bands on penguins. Proc R Soc B 271:423–426
Godley BJ, Gücü AC, Broderick AC, Furness RW, Solomon SE (1998) Interaction between marine turtles and artisanal fisheries in the eastern Mediterranean: a probable cause for concern? Zool Middle East 16:48–64
Gómez de Segura A, Tomás J, Pedraza SN, Crespo EA, Raga JA (2003) Preliminary patterns of distribution and abundance of loggerhead sea turtles, Caretta caretta, around Columbretes Islands Marine Reserve, Spanish Mediterranean. Mar Biol 143:817–823
Gómez de Segura A, Tomás J, Pedraza SN, Crespo EA, Raga JA (2006) Abundance and distribution of the endangered loggerhead turtle in Spanish Mediterranean waters and the conservation implications. Anim Conserv 9:199–206
Hays GC, Äkesson B, Godley BJ, Luschi P, Santidrian P (2001) The implications of location accuracy for the interpretation of satellite-tracking data. Anim Behav 61:1035–1040
Hochscheid S, Bentivegna F, Bradai MN, Hays GC (2007) Overwintering behaviour in sea turtles: dormancy is optional. Mar Ecol Prog Ser 340:287–298
Ivlev VS (1961) Experimental ecology of the feeding of fishes. Yale University Press, New Haven
Jribi I, Echwhiki K, Bradai MN, Bouain A (2008) Incidental capture of sea turtles by longlines in the Gulf of Gabès (South Tunisia): a comparative study between bottom and surface longlines. Sci Mar 72:337–342
Kareiva PM, Shigesada N (1983) Analysing insect movement as a correlated random walk. Oecologia 56:234–238
Lewison RK, Freeman SA, Crowder LR (2004) Quantifying the effects of fisheries on threatened species: the impact of pelagic longlines on loggerhead and leatherback sea turtles. Ecol Lett 7:221–231
Luschi P, Hays GC, Del Seppia C, Marsh R, Papi F (1998) The navigational feats of green sea turtles migrating from Ascension Island investigated by satellite telemetry. Proc R Soc Lond Ser B Biol Sci 265:2279–2284
Lutcavage ME, Lutz PL (1997) Diving physiology. In: Lutz PL, Musick JA (eds) The biology of sea turtles. CRC Press, Boca Raton, pp 387–410
Margaritoulis D, Argano R, Baran I, Bentivegna F, Bradai MN, Camiñas JA, Casale P, De Metrio G, Demetropoulos A, Gerosa G, Godley BJ, Haddoud DA, Houghton J, Laurent L, Lazar B (2003) Loggerhead turtles in the Mediterranean sea: present knowledge and conservation perspectives. In: Bolten AB, Witherington BE (eds) Loggerhead sea turtles. Smithsonian Books, Washington, DC, pp 175–198
Revelles M, Cardona L, Aguilar A, San Félix M, Fernández G (2007a) Habitat use by immature loggerhead sea turtles in the Algerian Basin (western Mediterranean): swimming behaviour, seasonality and dispersal pattern. Mar Biol 151:1501–1515
Revelles M, Isern-Fontanet J, Cardona L, San Félix M, Carreras C, Aguilar A (2007b) Mesoscale eddies, surface circulation and the scale of habitat selection by immature loggerhead sea turtles. J Exp Mar Biol Ecol 347:41–57
Revelles M, Cardona L, Aguilar A, Fernández G (2007c) The diet of pelagic loggerhead sea turtles (Caretta caretta) off the Balearic archipelago (western Mediterranean): relevance of long-line baits. J Mar Biol Assoc UK 87:805–813
Revelles M, Camiñas JA, Cardona L, Parga M, Tomás J, Aguilar A, Alegre F, Raga A, Bertolero A, Oliver G (2008) Tagging reveals limited exchange of immature loggerhead sea turtles (Caretta caretta) between regions in the western Mediterranean. Sci Mar 72:511–518
Smith WHF, Sandwell DT (1997) Global seafloor topography from satellite altimetry and ship depth soundings. Science 277:1957–1962
Strauss RE (1979) Reliability estimates of Ivlev’s electivity index, the forage ratio, and a proposed linear index of food selection. Trans Am Fish Soc 111:517–522
Tomás J, Aznar FJ, Raga JA (2001) Feeding ecology of the loggerhead turtle Caretta caretta in the western Mediterranean. J Zool Soc Lond 255:525–532
Tomás J, Gozalbes P, Raga JA, Godley BJ (2008) Bycatch of loggerhead sea turtles: insights from 14 years of stranding data. Endang Species Res 5:161–169
Turchin P (1991) Translating foraging movements in heterogeneous environments into the spatial distribution of foragers. Ecology 72:1252–1266
Zar JH (1999) Biostatistical analysis. Prentice-Hall, Englewood Cliffs
Acknowledgments
This project was partially financed by Capital Energy. The authors would like to thank the staff of Parc Natural del Delta de l’Ebre (Spain), Centro de Recuperación La Granja de el Saler of the Conselleria de Medio Ambiente, Urbanismo y Vivienda de la Generalitat Valenciana (Spain) and Le Seaquarium du Grau-du-Roi (France) for reporting the location of the stranded and bycaught turtles. J. Tomás is supported by a Marie Curie Postdoctoral Fellowship.
Author information
Authors and Affiliations
Corresponding author
Additional information
Communicated by U. Sommer.
Rights and permissions
About this article
Cite this article
Cardona, L., Revelles, M., Parga, M.L. et al. Habitat use by loggerhead sea turtles Caretta caretta off the coast of eastern Spain results in a high vulnerability to neritic fishing gear. Mar Biol 156, 2621–2630 (2009). https://doi.org/10.1007/s00227-009-1288-9
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00227-009-1288-9