Hostname: page-component-78c5997874-xbtfd Total loading time: 0 Render date: 2024-11-18T08:38:23.637Z Has data issue: false hasContentIssue false
  • English
  • Français

Influence of environmental and fishery parameters on loggerhead sea turtle by-catch in the longline fishery in the Azores archipelago and implications for conservation

Published online by Cambridge University Press:  17 June 2010

R.L. Ferreira ,
H.R. Martins ,
A.B. Bolten ,
M.A. Santos  and
K. Erzini
R.L. Ferreira
Affiliation:
Faculdade de Ciências e Tecnologia, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
H.R. Martins*
Affiliation:
Department of Oceanography and Fisheries, University of the Azores, 9901-862 Horta, Azores, Portugal
A.B. Bolten
Affiliation:
Archie Carr Center for Sea Turtle Research and Department of Biology, University of Florida, Gainesville, FL 32611, USA
M.A. Santos
Affiliation:
Department of Oceanography and Fisheries, University of the Azores, 9901-862 Horta, Azores, Portugal
K. Erzini
Affiliation:
Centre of Marine Sciences (CCMAR), University of Algarve, 8005-139 Faro, Algarve, Portugal
*
Correspondence should be addressed to: H.R. Martins, Department of Oceanography and Fisheries, University of the Azores, 9901-86 Horta, Azores, Portugal email: hrmartins@oma.pt
Get access Rights & Permissions [Opens in a new window]

Abstract

Oceanic juvenile loggerhead sea turtles, Caretta caretta, foraging in Azorean waters, are incidentally caught in drifting longlines that target swordfish, Xiphias gladius, and blue shark, Prionace glauca. Data were recorded during a longline gear modification experiment conducted in 2000. The results show that the captures are not uniformly distributed in relation to fishing effort, with 81% of the loggerheads (N = 232) caught in one-third of the sets (N = 93). The highest turtle catch rates were around the eastern group of islands, an area characterized by the presence of mesoscale eddies induced by bathymetric features. High catch rates coincided with the presence of the thermohaline front, between August and October, and when targeting blue shark. To investigate the causes of these differences we fitted a general linear model to evaluate the influence of mean depth, minimum depth, sea surface temperature (SST), soak area, soak time, moon phase and wind force on turtle and target species catch rates. These results revealed that mean depth and SST were most important for loggerhead catch rates, while minimum depth was the only significant variable for swordfish and mean depth, SST, wind force, moon phase and soak time influenced blue shark catches. The distribution of loggerhead sea turtles can be predicted by monitoring fishing areas in relation to bathymetry and SST. The impact of longline fishing could be greatly and quickly reduced by regulating the blue shark fishery and by increasing fishermen awareness for sea turtle conservation.

Keywords

Caretta carettaoceanic stage juvenilesby-catchswordfishblue sharklongline fisheryAzores
Type
Research Article
Information
Journal of the Marine Biological Association of the United Kingdom , Volume 91 , Issue 8 , December 2011 , pp. 1697 - 1705
Copyright
Copyright © Marine Biological Association of the United Kingdom 2010

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Aires-da-Silva, A., Ferreira, R.L. and Pereira, J.G. (2008) Blue shark catch rate patterns from the Portuguese longline fishery in the Azores. In Pikitch, E.K. and Camhi, M. (eds) Sharks of the open ocean. Oxford: Blackwell Publishing, pp. 230–234.Google Scholar
Báez, J.C., Raimundo Real, P. and Caminas, A. (2007) Differential distribution within longline transects of loggerhead turtles and swordfish captured by the Spanish Mediterranean surface longline fishery. Journal of the Marine Biological Association of the United Kingdom 87, 801–803.Google Scholar
Bakun, A. (1996) Patterns in the ocean. La Paz, Mexico: California Sea Grant College, CIB.Google Scholar
Beverly, S. and Robinson, E. (2004) New deep setting longline technique for by catch mitigation. AFMA report number R03/1398. Secretariat of the Pacific Community, Noumea, New Caledonia, 30 pp.Google Scholar
Bigelow, K.A., Boggs, C.H. and He, X. (1999) Environmental effects on swordfish and blue shark catch rates in the US North Pacific longline fishery. Fisheries Oceanography 8, 178–198.Google Scholar
Bjorndal, K.A., Bolten, A.B. and Martins, H.R. (2000) Somatic growth model of juvenile loggerhead sea turtles Caretta caretta: duration of pelagic stage. Marine Ecology Progress Series 202, 265–272.Google Scholar
Bolten, A.B. (2003) Active swimmers passive drifters: the oceanic juvenile stage of loggerheads in the Atlantic system. In Bolten, A.B. and Witherington, B.E. (eds) Loggerhead sea turtles. Washington, DC: Smithsonian Institution Press, pp. 63–68.Google Scholar
Bolten, A.B., Martins, H.R., Bjorndal, K.A. and Gordon, E.J. (1993) Size distribution of pelagic stage loggerhead sea turtles (Caretta caretta) in the waters around Azores and Madeira. Arquipélago. Life and Marine Sciences 11A, 49–54.Google Scholar
Bolten, A.B., Bjorndal, K.A., Martins, H.R., Dellinger, T., Biscoito, M.J., Encalada, S.E. and Bowen, B.W. (1998) Transatlantic developmental migrations of loggerhead sea turtles demonstrated by mtDNA sequence analysis. Ecological Applications 8, 1–7.CrossRefGoogle Scholar
Bolten, A.B., Martins, H.R. and Bjorndal, K.B. (eds) (2000) Workshop to design an experiment to determine the effects of longline gear modifications on sea turtle bycatch rates: Horta, Faial, Azores, Portugal, 2–4 September 1998. NOAA Technical Memorandum, 50 pp.Google Scholar
Bolten, A.B., Martins, H.R., Isidro, E., Santos, M.R., Ferreira, R.L., Bettencourt, E., Giga, A., Cruz, A. and Bjorndal, K. (2004) Experiment to evaluate gear modification on rates of sea turtle bycatch in the swordfish longline fishery in the Azores—Phase 1 and Phase 2. In Long, K.J. and Schroeder, B.A. (eds) Proceedings of the international technical expert workshop on marine turtle bycatch in longline fisheries. NOAA Technical Memorandum NMFS-OPR-26, pp. 139–153.Google Scholar
Carey, F.G. and Scharold, J.V. (1990) Movements of blue sharks (Prionace glauca) in depth and course. Marine Biology 106, 329–342.CrossRefGoogle Scholar
Carr, A. (1986) Rips, fads, and little loggerheads. BioScience 36, 92–100.Google Scholar
Carranza, A., Domingo, A. and Estrades, A. (2006) Pelagic longlines: a threat to sea turtles in the Equatorial Eastern Atlantic. Biological Conservation 31, 52–57.CrossRefGoogle Scholar
Crouse, D.T., Crowder, L.B. and Caswell, H. (1987) A stage-based population model for loggerhead sea turtles and implications for conservation. Ecology 68, 1412–1423.Google Scholar
Ferreira, R.L. (1999) Caracterização das capturas acessórias da pesca dirigida ao espadarte (Xiphias gladius) nos Açores. BSc thesis. University of Algarve, Portugal.Google Scholar
Ferreira, R.L. (2005) Caracterização das capturas de tartaruga careta (Caretta caretta) e influência de parâmetros ambientais e pesqueiros, na pesca dirigida ao espadarte (Xiphias gladius) nos Açores. MSc thesis. University of Algarve, Portugal.Google Scholar
Ferreira, R.L., Martins, H.R., Bolten, A.B. and Silva, A. (2001) Impact of longline fishing on sea turtle bycatch in Azores. Arquipélago. Life and Marine Sciences 18A, 75–79.Google Scholar
Ferreira, R.L., Santos, M.R., Martins, H.R., Bolten, A.B., Isidro, E., Giga, A. and Bjorndal, K. (2003) Accidental captures of loggerhead sea turtles by the Azores longline fishery in relation to target species and gear retrieving time. Proceedings of the 22nd annual symposium on sea turtle biology and conservation, Miami, USA, 4–7 April 2002. NOAA Technical Memorandum, NMFS-SEFSC-503, 261–262.Google Scholar
ICCAT (1997) Report of the ICCAT swordfish stock assessment session. Halifax, Canada, October 2–9, 1996. Collective Volume of Scientific Papers 46, 165–285.Google Scholar
Lewinson, R.L., Freeman, S.A. and Crowder, L.B. (2004) Quantifying the effects of fisheries on threatened species: the impact of pelagic longlines on loggerhead and leatherback sea turtles. Ecology Letters 7, 221–231.CrossRefGoogle Scholar
Long, K.J. and Schroeder, B.A. (eds) (2004) Proceedings of the International Technical Expert Workshop on Marine Turtle Bycatch in Longline Fisheries. US Department of Commerce, NOAA Technical Memorandum NMFS-F/OPR-26, 189 pp.Google Scholar
Mailly, T., Blayo, E. and Verron, J. (1997) Assessment of the ocean circulation in the Azores region as predicted by a numerical model assimilating altimeter data from Topex/Poseidon and ERS-1 satellites. Annales Geophysicae 15, 1354–1368.Google Scholar
Marques, M.R. (2001) Navegar. 2nd edition. Europa-América.Google Scholar
Martins, H., Bolten, A. and Ferreira, R. (2001) Impact of longline fisheries on sea turtles in the archipelago of the Azores. In Ciccione, S., Ross, D. and Gall, J.Y. (eds) Advance in knowledge and conservation of sea turtles in south-west Indian Ocean. La Réunion 28 Nov.–2 Dec. 1999. Etudes et Colloques du Editions du Centre d'Etude et de Découverte des Tortues Marine de La Reunión 1, pp. 76–77.Google Scholar
Polovina, J.J., Kobayashi, D.R., Parker, D.M., Seki, M.P. and Balazs, G.H. (2000) Turtles on the edge: movement of loggerhead turtles (Caretta caretta) along oceanic fronts, spanning longline fishing grounds in the central North Pacific, 1997–1998. Fisheries Oceanography 9, 71–82.Google Scholar
Polovina, J.J., Howell, E., Kobayashi, D.R. and Seki, M.P. (2001) The transition zone chlorophyll front, a dynamic global feature defining migration and forage habitat for marine resources. Progress in Oceanography 49, 469–483.Google Scholar
Polovina, J., Balazs, G., Howell, E., Parker, D., Seki, M. and Dutton, P. (2004) Forage and migration habitat of loggerhead (Caretta caretta) and olive ridley (Lepidochelys olivacea) sea turtles in the central North Pacific Ocean. Fisheries Oceanography 13, 36–51.Google Scholar
Santos, R.S., Hawkins, S., Monteiro, L.R., Alves, M. and Isidro, E.J. (1995) Marine research, resources and conservation in the Azores. Aquatic Conservation: Marine and Freshwater Ecosystems 5, 311–354.CrossRefGoogle Scholar
Santos, M.R., Bolten, A.B., Martins, H.R., Gonçalves, J. and Ferreira, R.L. (2007a) Distribution patterns of sea turtles caught during an experimental longline fishery. Proceedings of the 25th Annual Sea Turtle Symposium, Savannah, USA, 18–22 January 2005. NOAA Technical Memorandum.Google Scholar
Santos, M.R., Bolten, A.B., Martins, H.R., Riewald, B. and Bjorndal, K.A. (2007b) Air-breathing visitors to seamounts: sea turtles. In Pitcher, T.J., Morato, T., Hart, P.J.B., Clark, M., Haggan, N. and Santos, R.S. (eds) Seamounts: ecology, fisheries and conservation. Oxford: Blackwell Publishing, pp. 239–244.Google Scholar
Serpa, M. (2000) Information on accidental capture of marine turtles in the Azores. In Bolten, A.B., Martins, H.R. and Bjorndal, K.B. (eds) Workshop to design an experiment to determine the effects of longline gear modifications on sea turtle bycatch rates. NOAA Technical Memorandum, pp. 17–21.Google Scholar
Simões, P.R. (1995) The swordfish (Xiphias gladius L. 1758) fishery in the Azores, from 1987 to 1993. Collected Volume of Scientific Papers, ICCAT SCRS/94/109 44, 126–131.Google Scholar
StatSoft Inc (1999) Statistica for Windows. Computer Program Manual, Tulsa, USA.Google Scholar
Watson, J., Foster, D., Epperly, S. and Shah, A. (2004) Experiments in the western Atlantic northeast distant waters to evaluate sea turtle mitigations measures in the pelagic longline fishery. Report on experiments conducted in 2001–2003, NOAA Fisheries, 123 pp.Google Scholar
Witherington, B., Kubilis, P. and Brost, B. (2009) Decreasing annual nest counts in a globally important sea turtle population. Ecological Applications 19, 30–54.Google Scholar
Zar, J.H. (1996) Biostatistical analysis. 3rd edition. Upper Saddle River, NJ: Prentice-Hall.Google Scholar