Shark Depredation and Unwanted Bycatch in Pelagic Longline

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Shark Depredation and Unwanted Bycatch in Pelagic Longline Fisheries Table A8.1. Effort data for the Hawaii-based longline tuna and swordfish fisheries, 1987 – 2004 (Western Pacific Regional Fishery Management Council, 2005a; Clemens, 2006). Year Number of active vessels Number of trips Number of hooks set (millions) 1987 37 Not known Not known 1988 50 Not known Not known 1989 88 Not known Not known 1990 138 Not known Not known 1991 141 1,671 12.3 1992 123 1,266 11.7 1993 122 1,192 13.0 1994 125 1,106 12.0 1995 110 1,125 14.2 1996 103 1,100 14.4 1997 105 1,125 15.6 1998 114 1,140 17.4 1999 119 1,138 19.1 2000 125 1,103 20.3 2001 101 1,034 22.4 2002 100 1,165 27.0 2003 110 1,215 29.9 2004 125 1,338 32.0 2005 125 1,533 34.9 Table A8.2 summarizes the general fishing methods and gear of the contemporary Hawaii-based longline tuna and swordfish fisheries. The information in Table A8.2 is intended to provide a generalized characterization of the Hawaii longline fleet. However, the longline gear configurations and fishing methods are not consistent between Hawaii vessels. For instance, the color of main and branch lines, weight amount and location, type of buoys, vessel horsepower, trip length and fishing days, vary between vessels. A8.3. Catch and Discard Rates of Target and Bycatch Species Table A8.3 summarizes CPUE of all caught (retained and discarded) fish species for combined Hawaii-based longline tuna and swordfish fisheries. Table A8.4 presents the total catch by weight and value of the Hawaii-based longline swordfish and tuna fisheries for 1987-2004. Table A8.5 presents the catch composition for the Hawaii longline fleet by weight and value for 2001. The annual average catch of blue, mako, thresher, and other sharks in Hawaii longline fisheries from 1987-2004 was 1,579,700 lb, 137,700 lb, 114,400 lb, and 101,400 lb, respectively, with a combined annual average weight of 1,933,200 lb (Western Pacific Regional Fishery Management Council, 2005a). In 2001, pelagic sharks comprised about 50% of the catch composition of swordfish longline sets, compared to 16% for tuna sets (Ito and Machado, 2001). Shark CPUE has been about 10 times higher in shallow sets targeting swordfish compared to sets targeting tuna (Ito and Machado, 1999). Since regulations designed to reduce interactions with sea turtles in the Hawaii-based pelagic longline swordfish fishery came into effect in May 2004, which required the fleet to switch from using a 9/0 J hook with squid bait to a wider 18/0 10 degree offset circle hook with fish bait, there has been a significant 36% decrease in shark (combined species) CPUE relative to the period before the sea turtle regulations came into effect (Gilman et al., 2006a). From 1994 – 2002, the period before the sea turtle regulations came into effect, shark CPUE for the Hawaii-based longline swordfish fishery was 21.9 sharks per 1000 hooks (20.4 – 23.5 95% CI). From 2004 – 2006, the period since the sea turtle regulations have been in effect, shark CPUE was 14.0 sharks per 1000 hooks (13.6 – 14.5 95% CI). Based on research conducted in the Azores longline swordfish and blue shark fishery (Bolten and Bjorndal 2002) and U.S. North Atlantic longline swordfish fishery (Watson et al., 2005), this observed decrease in shark CPUE is likely due to the fleet’s change from using squid to mackerel for bait. From 1994 – 2006, observer data show that blue sharks comprised 92.6% of total caught sharks in Hawaii longline swordfish targeting sets. From 1994 – 2006, observer data show that blue sharks comprised 82.2% of total caught sharks in Hawaii longline tuna targeting sets. From 1993 – 2000, logbook data show that blue sharks comprised an average of 87.5% of total reported shark catch, with an average of 3,509 lbs of blue sharks caught annually (Western Pacific Regional Fishery Management Council, 2005a). From 2001 – 2004, blue sharks comprised an average of 18.4% of total reported shark catch, with an average of 65,500 lbs of blue shark caught annually (Western Pacific Regional Fishery Management Council, 2005a). The Hawaii-based longline swordfish fishery was closed from February 2002- May 2004 due to concerns over interactions with sea turtles (Gilman et al., 2006a,b), which explains the substantial drop in weight and proportion of blue shark catch during this period. Table A8.6 presents statistics from logbook data on shark bycatch in combined Hawaii-based longline tuna and swordfish fisheries from 1994-1999 and for 2004. Table A8.7 presents statistics for only observed sets targeting swordfish by Hawaii-based longline vessels on the condition of sharks when hauled to the vessel, condition of discarded sharks, and number and proportion of retained sharks. Table A8.8 presents similar statistics from observer data for observed sets targeting tuna. An increase in demand for shark fins, resulting from increasing income in China, and increased demand from the U.S. mainland for Hawaii shark fins as the supply from U.S. Atlantic coastal shark fisheries declined due to significant reductions in shark quotas, are believed to explain the gradual increase in percent of caught sharks that were finned from 1994-1999 (McCoy and Ishihara, 1999; U.S. National Marine Fisheries Service, 2001). In 1999, before restrictions on shark finning were instituted, 65.4% of caught sharks were finned while carcasses of only 1.1% of caught sharks were retained for combined Hawaii longline fisheries (U.S. National Marine Fisheries Service, 2001). The Shark Finning Prohibition Act came into effect in March 2002, which explains the sudden drop in retention of only fins from caught sharks. Whole shark carcasses have been a stable and insignificant component of shark landings, typically representing < 1% of shark catch. Hawaii longliners generally only retain carcasses of mako and thresher 122
USA Hawaii-based Pelagic Longline Swordfish and Tuna Fisheries Table A8.2. Fishing gear and methods of the Hawaii-based pelagic longline swordfish and tuna fisheries (U.S. National Marine Fisheries Service Pacific Islands Fisheries Science Center, Unpublished Data; Boggs, 1992; Pacific Ocean Producers, 2005; Ito and Machado, 2001; U.S. National Marine Fisheries Service, 2001; Brothers and Gilman, 2006). Fishing Gear and Method Hawaii Longline Tuna Vessel Hawaii Longline Swordfish Vessel Trip duration 21 days 30 days Number of sets per trip 10 17 Number of trips per year 15 Annual swordfish effort is capped at 2,120 sets or until turtle interaction caps are reached, whichever threshold is reached first. From 1991- 2001 vessels targeting swordfish or a combination of swordfish and yellowfin tuna made an average of 11.8 trips per year. Since 2004 there has been an annual fishery-wide cap of 2,120 sets or until caps on turtle interactions are reached, whichever cap is reached first. In 2006 the fishery reached a cap on loggerhead sea turtles after 3 months. Fishing grounds Fishing season(s) From January through March, effort is concentrated between latitudes 15 N and 35 N and longitudes 150 W and 180. From April through June tuna fishing effort expands to the south and spreads further east and west to about longitudes 145 W and 170 E. Year-round Primarily the area to the northeast of the Hawaiian Islands on the high seas in the North Pacific Transition Zone. Can be year-round but effort tends to be highest in the first quarter of the year, and due to an annual cap on turtle interactions and effort, the swordfish fishery can be closed for the year once either of these caps is reached Mainline material Nylon monofilament Nylon monofilament Mainline length Average of 54 km 30 to 100 km Mainline deployment Mainline shooter (to set mainline slack) Manual (no shooter, to set mainline taught) Distance between buoys 800 m 500 m Distance from buoy to mainline (float line length) 22 m (required to be > 20 m) 8 m Average branch line length 13 m 17 m Branch line material Nylon monofilament Nylon monofilament Wire trace or leader on branch lines Yes (0.5 m length) No Number of hooks between buoys 15 to 40 4 to 6 Average maximum depth of hooks when set 234 m 69 m Average maximum depth of mainline when set 221 m 52 m Mainline sink rate 10 m per minute 4 m per minute Timing of set, soak, and haul Gear is set in the morning, soaks during the day, and is hauled before dark. Gear is set in the evening no earlier than 1 hour after local sunset, soaks overnight, and is hauled the following morning no later than local sunrise. Lightstick use No (prohibited) One lightstick every 1 to 5 hooks Number of hooks per set 1,200 to 3,000 700 to 1,000 Hook setting interval 6-8 seconds per hook 12 seconds per hook Radio beacons 6 per set 6 per set Hook type Weight size and location Japan tuna 3.6 ring hook, 14/0, 15/0, and 16/0 circle hooks with 10 degree offset 45-80 g weighted swivels located within 1 m of the hook Clip size and type 145 mm 148-1/8” x 8/0 145 mm 148-1/8” x 8/0 Bait type Mackerel, saury, sardine Mackerel, saury, sardine Number of crew Captain and 3 crew Captain and 4 to 5 crew Vessel Monitoring System Yes Yes 18/0 circle hooks with a 10 degree offset (required) 0 to 80 g weighted swivels attached 5 to 7 m from hook (if weight is attached it is usually attached at the midpoint of the branch line) (in 2005 all swordfish vessels used weighted swivels on branch lines) 123
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Shark Depredation and Unwanted Byca
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Contents Summary and Conclusions 1
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Contents Appendix 3. Fiji Pelagic L
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Contents Appendix 8. USA Hawaii Lon
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Chapter 1 Introduction and Methods
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Introduction and Methods 1.2. Metho
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Fishing Gear and Operational Charac
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Fishing Gear and Operational Charac
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Shark Catch Rates and Disposition T
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Chapter 4 National and Internationa
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National and International Measures
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Economic, Practical, Ecological and
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Economic, Practical, Ecological and
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Chapter 6 Industry Attitudes and Pr
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Industry Attitudes and Practices Lo
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Industry Attitudes and Practices Fi
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Chapter 7 Potential of Deterrents,
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Potential of Deterrents, Hotspot Av
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References Campana, S.E., L. Marks,
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References Neves dos Santos, M., Ga
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Page 99 and 100: Appendix 5 Japan Pelagic Longline F
Page 101 and 102: Japan Pelagic Longline Fisheries Fi
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Page 105 and 106: Japan Pelagic Longline Fisheries Ta
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Page 115 and 116: Appendix 6 Peru Artisanal Mahimahi
Page 117 and 118: Peru Artisanal Mahimahi And Shark L
Page 127 and 128: Appendix 7 South Africa Pelagic Lon
Page 129 and 130: South Africa Pelagic Longline Tuna
Page 135: Appendix 8 USA Hawaii-based Pelagic
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Page 147 and 148: Appendix 9 USA Atlantic, Gulf of Me
Page 149 and 150: USA Atlantic, Gulf of Mexico and Ca
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Shark Depredation and Unwanted Bycatch in Pelagic Longline

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