Differential loggerhead by-catch and direct mortality due to surface longlines according to boat strata and gear type
DOI:
https://doi.org/10.3989/scimar.2006.70n4661Keywords:
Caretta caretta, drifting longline, fisheries, incidental capture, pre-release mortality, sea turtleAbstract
Surface longline gears are used to fish different species, mainly albacore Thunnus alalunga (Bonnaterre, 1788), bluefin tuna Thunnus thynnus (Linnaeus, 1758), and swordfish Xiphias gladius Linnaeus, 1758, and are considered highly dangerous for threatened marine turtles. Loggerheads Caretta caretta (Linnaeus, 1758) can be incidentally captured by surface longlines. A number of captured individuals die during the fishing operation, which we consider direct mortality due to fishing. We analysed the relative loggerhead by-catch and direct mortality associated with each type of boat and gear from April to December during the period 1999-2004 in the Spanish surface longline fleet that fishes in the western Mediterranean Sea, an important fishing area for this fleet. We used different indices to compute the catch per unit effort (CPUE) according to the number of hooks and to the number of fishing operations for each type of boat and gear. Both by-catch and direct mortality differed significantly according to the type of boat and gear. With respect to the number of hooks, boats longer than 12 m not using a roller and targeting bluefin tuna captured the highest number of loggerheads, whereas boats longer than 12 m with a roller that targeted swordfish caused the highest direct mortality. With respect to the number of fishing operations, boats longer than 12 m without a roller that targeted albacore captured the highest number of loggerheads; the highest direct mortality was caused by this type of boat and by boats longer than 12 m using a roller and targeting swordfish.
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References
Aguilar, R., J. Mas and X. Pastor. – 1992. Impact of Spanish swordfish longline fisheries on the loggerhead sea turtle Caretta caretta population in the western Mediterranean. In: J.I. Richardson, and T.H. Richardson (eds.), Proceedings of the 12th annual workshop on sea turtle biology and conservation, pp. 25-29. NOAA Tech. Memo., NMFS, SEFSC 361.
Báez, J.C., J.A. Camiñas and L. Rueda. – 2006. Accidental fishing capture of marine turtles in South Spain. Mar. Turtle Newsl., 111: 11-12.
Camiñas, J.A. – 1997. Capturas accidentales de tortuga boba Caretta caretta (Linnaeus, 1758) en el Mediterráneo occidental en la pesquería de palangre de superficie de pez espada (Xiphias gladius Linnaeus, 1758). Collect. Vol. Sci. Pap. ICCAT, 4: 446-455.
Camiñas, J.A. and J.M. de la Serna. – 1995. The loggerhead distribution in the western Mediterranean Sea as deduced from captures by the Spanish longline fishery. In: G. A. Llorente, A. Montori, X. Santos and M. A. Carretero, (eds.). Sci. Herpet., 316-323.
Camiñas, J.A., J.M. de la Serna and E. Alot. – 1992. Loggerhead (Caretta caretta L.) frequency observed in the Spanish surface long-line fisheries in the western Mediterranean Sea during 1989. Rapp. Comm. Int. Mer Médit., 33: 286.
Camiñas, J.A. and X. Valeiras. – 2001. Proyecto europeo para la evaluación de las capturas accidentales de tortugas marinas en las pesquerías de palangre de superficie y arrastre en el Mediterráneo (EMPT). Primeros resultados. 1ª Simposium de la Sociedad Española de Cetáceos, Ceuta, 23-27 febrero 2000. Libro de resúmenes: 5-9.
Chaloupka, M., D. Parker and D. Balazs. – 2004. Modelling postrelease mortality of loggerhead sea turtles exposed to the Hawaii-based pelagic longline fishery. Mar. Ecol. Prog. Ser., 280: 285-293. doi:10.3354/meps280285
Cheng, J.J. and T.H. Chen. – 1997. The incidental capture of 5 species waters of Taiwan. Biol. Conserv., 82: 235-239. doi:10.1016/S0006-3207(97)00027-X
Julian, F. and M. Beenson. – 1998. Estimates of marine mammal, turtle and seabird mortality for 2 California gillnet fisheries 1990-1995. Fish. Bull., 96: 271-284.
Laurent, L., J.A. Camiñas, P. Casale, M. Deflorio, G. de Metrio, A. Kapantagakis, D. Margaritoulis, C.Y. Politou and X. Valeiras. – 2001. Assessing marine turtle bycatch in European drifting longline and trawl fisheries for identifying fishing regulations. Project-EC-DG Fisheries 98-008. Joint project of BIOINSIGHT, IEO, IMBC, STPS and University of Bari. Villeurbanne, France. Available online in: http://www.seaturtle.org/).
Lewison, R.L., S.A. Freeman and L.B. Crowder. – 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. doi:10.1111/j.1461-0248.2004.00573.x
Poiner, J.J. and A.N.M. Harris. – 1996. The incidental capture, direct mortality and delayed mortality of turtles in Australia’s northern praws fishery. Mar. Biol., 125: 813-193. doi:10.1007/BF00349264
Robins, J.B. – 1995. Estimated catch and mortality of sea turtles from the east coast otter trawl fishery of Queensland, Australia. Biol. Conserv., 74: 157-167. doi:10.1016/0006-3207(95)00025-Y
Silvani, L., M. Gazo and A. Aguilar. – 1999. Spanish drifnet fishing and incidental catches in the western Mediterranean. Biol. Conserv., 90: 79-85. doi:10.1016/S0006-3207(98)00079-2
UICN. – 2001. Categories and criticism of the red list, of the UICN: Version 3.1. UICN, Gland, Switzerland and Cambridge, England.
Valeiras, J. and J.A Camiñas. – 2003. The incidental capture of seabirds by Spanish drifting longline fisheries in the Western Mediterranean Sea. Sci. Mar., 67(Suppl. 2): 65-68.
Wetheral, J.A. – 1977. Mortality of sea turtles in Hawaii longline fishery: a preliminary assessment of population impacts. NOAA, NMFS, SWFSC, Honolulu Laboratory, Honolulu, HI. Administrative Report H-97-07. 51 pp.
Work, T.M. and G.H. Balazs. – 2002. Necropsy findings in sea turtles taken as by-catch in the North Pacific longline fishery. Fish. Bull., 100: 876-880.
Witzell, W.N. – 1999. Distribution and relative abundance of sea turtles caught incidentally by the U.S. pelagic longline fleet in western North Atlantic Ocean, 1992-1995. Fish. Bull., 97: 200-211.
Yeung, C. – 1999. Estimates of marine mammal and marine turtle by-catch by the U.S. Atlantic pelagic longline fleet in 1998. NOAA Tech. Memo. NMFS-SEFSC-430. 26 pp.
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