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Shark Depredation and Bycatch in Pelagic Longline Fisheries Page 10 Table 3.1. Shark catch rate and disposition in 12 pelagic longline fisheries for the most current year for which data are available (Megalofonou et al., 2005; Alfaro-Shigueto et al., this volume; Brothers, this volume; Clarke, this volume; Gilman, this volume; Mangel and Alfaro-Shigueto, this volume; Petersen and Goren, this volume; Thomson, this volume). Pelagic Longline Fishery Shark Catch Rate (Number per 1000 hooks) Shark Retention (Fins and/or Carcass) (% of Total Number Caught Sharks) Australia Tuna and Billfish Longline Fishery 5.5 1 Not available Chile Artisanal Mahi Mahi and Shark Longline Fishery 24 2 > 99 2 Chile Longline Swordfish Fishery 8 2 > 99 2 Fiji Longline Tuna Fishery 1.1 78-90 Italy Mediterranean Industrial Longline Swordfish Fishery 0.74 Not available Japan Distant Water Longline Tuna Fishery 0.021 3 Not available Japan Offshore Longline Fishery 0.175 3 Not available Japan Nearshore Longline Fishery 0.020 3 Not available Peru Artisanal Longline Mahi Mahi and Shark Fishery during mahi season 0.99 84 South Africa Longline Tuna and Swordfish Fishery 4.0 80 USA - Hawaii tuna 2.2 2.1 USA - Hawaii swordfish 16.7 0.2 1 Rough estimate based on Australian Commonwealth Scientific and Research Organization unpublished data from a subset of the fleet and time period, possibly not representative (Brothers, this volume). 2 Rough estimate based on interview responses. 3 Based on number of sharks recorded in vessel logbooks (Clarke, this volume; Nakano and Clarke, 2006). The large number of “not available” entries and entries based on rough estimates in Table 3.1 suggests either that there is insufficient data collection and management measures for shark species or that relevant data are collected but have not been analyzed. For fisheries where there is high confidence in available shark catch rates, these range from 0.7 to 17 sharks per 1000 hooks. The location of fishing grounds and characteristics of fishing gear and methods are likely primary factors determining a fleet’s shark catch rate. Certain gear designs (e.g., use of a wire leader, use of squid for bait, and depth of baited hooks) contribute to high shark catch rates. Shallow-setting pelagic longline fisheries generally have higher shark catch rates than deeper-setting fisheries. The proportion of total catch comprised of sharks by number varies widely for the fisheries included in this study. In the Australia longline tuna and billfish fishery, sharks comprise about 27% of the total catch (Brothers, this volume). Observer data from 1999 found that sharks comprised > 25% of the total number of fish caught by Fiji longline tuna vessels (Swamy, 1999), while Secretariat of the Pacific Community observer program data for 1999 and 2002-2005 found that sharks comprised only 5.5% of the total number of caught fish (Thomson, this volume). From 1998-1999, sharks comprised about 18% of the
Page 11 Shark Depredation and Bycatch in Pelagic Longline Fisheries total catch in the Italy Mediterranean industrial longline swordfish fishery (Megalofonou et al., 2005). In the Peru artisanal longline mahi mahi and shark fishery, during the mahi mahi season in the port of Ilo for 2005-2006, sharks comprise less than 1% of the total catch by number (Mangel and Alfaro-Shigueto, this volume). In the South Africa longline tuna and swordfish fishery, from 1998-2005, sharks comprised 16.2% of the total number of caught fish (Petersen and Goren, this volume). In 2001, pelagic sharks comprised about 50% of the catch composition of swordfish sets and 16% for tuna sets in the Hawaii longline fishery (Ito and Machado, 2001). However, since 2004 the shark catch rate in the swordfish fishery dropped 36% when the fishery was required to switch from using J hooks with squid bait to wider circle hooks with fish bait (Gilman et al., 2006a). The results from this study are generally consistent with the literature, which shows that a large quantity of pelagic sharks is taken as bycatch in pelagic longline fisheries with tuna and swordfish as their primary target species (Bailey et al., 1996; Williams, 1997; Matsunaga and Nakano, 1999; Swamy, 1999; Francis et al., 2001; Beerkircher et al., 2002). For example, in the western Pacific, shark species account for the highest category of bycatch in tropical fisheries, where sharks comprise 27% of total bycatch, and in subtropical fisheries, where sharks are 18% of total bycatch (Bailey et al., 1996; Heberer and McCoy, 1997). In the U.S. Atlantic longline swordfish and tuna fisheries, sharks and rays constituted 25% of total catch between 1992 and 2003 (Abercrombie et al., 2005). Beerkircher et al. (2002) found that sharks comprised 15% of the total catch, comprised of 22 elasmobranch species, in the southeastern U.S. pelagic longine swordfish and tuna fisheries. Bonfil (2002) found that the same numbers of sharks are caught in directed fisheries as are caught as bycatch mostly in longline tuna fisheries. However, the recent development of longline directed shark fisheries, especially in the Pacific, may mean that directed shark fisheries are now catching more sharks (Chen et al., 2002; Stevens, 2002; Catarci, 2004; FAO, 2006; Alfaro-Shigueto et al., this volume; Mangel and Alfaro-Shigueto, this volume). For fisheries where information on shark catch composition is available, blue sharks comprise the largest proportion of shark catch. Blue sharks comprise 47% of total shark catch by number of fish in the Australia longline tuna and billfish fishery (Brothers, this volume); 49% in the Fiji longline tuna fishery (Thomson, this volume); > 70% of total shark catch by number for Japan longline fisheries (Clarke, this volume); 57% for the Peru artisanal mahi mahi and shark longline fishery (Pro Delphinus, unpublished data); 69% for the South Africa longline tuna and swordfish fishery (Petersen and Goren, this volume); and 82% and 92% for the U.S.A. Hawaii longline tuna and swordfish longline fisheries, respectively (Gilman, this volume). Identifying effective and commercially viable methods to reduce unwanted shark bycatch in longline fisheries would contributes to reducing shark fishing mortality. Increasing discards of blue sharks in pelagic longline fisheries would likely reduce fishing mortality of this species, as blue sharks are usually alive when hauled to the vessel (Beerkircher et al., 2002; Gilman, this volume; Mangel and Alfaro- Shigueto, this volume; Thomson, this volume). Beerkircher et al. (2002) found that the condition of sharks caught in pelagic longline gear (dead versus alive when hauled to the vessel) varied widely by species, where for example, blue sharks had a relatively low 12.2% mortality, while silky sharks (the most dominant species of shark by number caught in the observed southeastern U.S. pelagic longline swordfish and tuna fisheries, 31.4% of elasmobranch catch) had a 66.3% mortality. Gilman (this volume) found that over 89% of sharks caught in the Hawaii-based longline swordfish fishery and over 93% of sharks caught in the Hawaii-based longline tuna fishery are alive when the gear is retrieved. Mangel and Alfaro-Shigueto (this volume) found that 87% of sharks caught in the Peru artisanal mahi mahi and shark longline fishery were alive when gear was retrieved. Thomson (this volume) analyzes Secretariat of the Pacific Community observer program data from 2002-2005 for the Fiji longline tuna fishery and found that over 94% of blue sharks and over 84% of combined species of sharks were alive when hauled to the vessel.
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Page 55 and 56: Appendix 1, Australia Page 41 Of th
Page 57 and 58: Appendix 1, Australia Page 43 A1.4.
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Appendix 1, Australia Page 61 30. D
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Appendix 1, Australia Page 63 been
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Appendix 1, Australia Page 65 The f
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Appendix 1, Australia Page 67 Shott
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Appendix 2, Chile Page 69 Captures
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Appendix 2, Chile Page 71 Landings
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Appendix 2, Chile Page 73 Table A2.
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Appendix 2, Chile Page 75 Fig. A2.5
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Appendix 2, Chile Page 77 A summary
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Appendix 2, Chile Page 79 Prices ar
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Appendix 2, Chile Page 81 Two of th
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Appendix 2, Chile Page 83 A2.14.6.
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Appendix 2, Chile Page 85 Fig. A2.1
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Appendix 2, Chile Page 87 A2.17. Re
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Appendix 3, Fiji Page 89 • Robert
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Appendix 3, Fiji Page 91 The data i
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Appendix 3, Fiji Page 93 Table A3.4
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Appendix 3, Fiji Page 95 A3.7.2. Pr
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Appendix 3, Fiji Page 97 Table A3.1
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Appendix 3, Fiji Page 99 of whale d
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Appendix 4, Italy Page 101 A4.2. Fl
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Appendix 4, Italy Page 103 Branch l
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Appendix 4, Italy Page 105 catch sp
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Appendix 4, Italy Page 107 Table A4
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Appendix 4, Italy Page 109 (many fi
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Appendix 5, Japan Page 111 Appendix
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Appendix 5, Japan Page 113 A5.2. Hi
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Appendix 5, Japan Page 115 SEA SURF
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Appendix 5, Japan Page 117 A5.3.1.
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Appendix 5, Japan Page 119 period (
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Appendix 5, Japan Page 121 Catch ('
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Appendix 5, Japan Page 123 areas du
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Appendix 5, Japan Page 125 When cut
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Appendix 5, Japan Page 127 o Anothe
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Appendix 5, Japan Page 129 the near
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Appendix 5, Japan Page 131 pieces w
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Appendix 5, Japan Page 133 Japanese
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Appendix 6, Peru Page 135 Appendix
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Appendix 6, Peru Page 137 While the
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Appendix 6, Peru Page 139 Pro Delph
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Appendix 6, Peru Page 141 Table A6.
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Appendix 6, Peru Page 143 Revenue f
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Appendix 6, Peru Page 145 of the ma
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Appendix 6, Peru Page 147 Over a th
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Appendix 6, Peru Page 149 Fig. A6.1
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Appendix 7, South Africa Page 151 A
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Appendix 7, South Africa Page 153 N
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Appendix 7, South Africa Page 155 A
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Appendix 7, South Africa Page 157 T
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Appendix 7, South Africa Page 161 T
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Appendix 8, Hawaii Page 163 Table A
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Appendix 8, Hawaii Page 165 Average
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Appendix 8, Hawaii Page 167 regulat
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Table A8.7. Shark capture statistic
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Appendix 8, Hawaii Page 171 A8.4. M
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Appendix 8, Hawaii Page 173 The pot
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Appendix 8, Hawaii Page 175 A8.7. O
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Appendix 8, Hawaii Page 177 A8.11.3
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Appendix 8, Hawaii Page 179 Pacific
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Shark Depredation and Bycatch in Pe
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