Shark Depredation and Unwanted Bycatch in Pelagic Longline

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Chapter 2 Fishing Gear and Operational Characteristics The scope of the 12 fisheries included in this study ranged from smallscale domestic artisanal fisheries to modern mechanized industrial fleets of distant water fishing nations. Some of these fisheries never target sharks and rarely retain caught sharks, while in other fisheries sharks are occasionally an important incidental catch species or can be an important target species. Table 2.1 summarizes the general gear and operational characteristics of each fishery included in the study, focusing on parameters that are likely to affect shark interactions. For instance, the number of hooks in a basket, float line length and branch line length will affect the depth of baited hooks when soaking, which affects shark catch rates. The material used for the trace (leader) will affect shark retention on branch lines. The type of bait used will affect shark catch rates. The information in Table 2.1 is intended to provide a generalized characterization of the gear of each fishery. However, for some parameters, there may be large variability in fishing gear and methods between vessels in a fleet and even for an individual vessel. For instance, some vessels in the Fiji longline tuna fleet fish at grounds within the Fiji Exclusive Economic Zone (EEZ), while larger vessels fish at grounds much more distant from their home port, on the high seas and in other nation’s EEZs, and these two categories of vessels have substantial differences in the gear characteristics (Thomson, this volume). In some fisheries, vessels will seasonally substantially alter their gear when they change their primary target species (e.g., Chile and Peru artisanal longline mahi mahi and shark fisheries, Alfaro-Shigueto et al., this volume, Mangel and Alfaro-Shigueto, this volume; Japan offshore and nearshore pelagic longline tuna fisheries, Clarke, this volume). Gear characteristics may also vary substantially between seaports within a fishery (Mangel and Alfaro-Shigueto, this volume; Japan offshore and nearshore pelagic longline tuna fisheries, Clarke, this volume). Due to the large and diverse nature of the fleets, and because the information is not available in many cases, it is not practical to summarize the Japanese distant water, offshore and nearshore longline fisheries in Table 2.1. Available information for these fleets is presented in Appendix 5. The following is a summary of the main gear and operational characteristics of each fishery included in the study that affect shark catch rates: • Australia longline tuna and billfish fishery: There are about 90 vessels, 15-30 m in length, in this year-round fishery. Trip length is typically four days or less. All but one of the vessels fish in waters off Australia’s east coast. Hooks are set at depths between 33-77 m. Regulations prohibit the use of a wire leader on branch lines. A variety of fish species and squid are used for bait. About 11% of bait is caught by vessels and held aboard alive in circulating tanks for extended periods. Lightsticks are used. Gear soaks through the night. • Chile artisanal longline mahimahi and shark fishery and longline swordfish fishery: (i) The artisanal fishery, with about 131 vessels with lengths < 18 m, targets mahi mahi during the austral summer when mahi mahi is more available and has a higher value than sharks, and targets sharks throughout the year. Trip length varies by season with mahi mahi-targeting trips typically lasting three to four days. The artisanal fishery, when targeting sharks, is restricted to grounds along Chile’s northern coast. Baited hooks are set at depths between 9-72 m. Wire leaders are used during the shark season. Bait species include sardine, mackerel and flying fish. Lightsticks are not used. Setting and hauling is conducted manually. Gear is set and soaks during the day. (ii) The industrial and artisanal swordfish fishery has 16 vessels with lengths ranging from 17-42 m. The fishery operates primarily from March to December. Vessels fish at grounds near Valparaiso and Concepcion at 80 o W longitude, between 16-40 o S latitude. Baited hooks are set at depths between 58-70 m. Wire leaders are typically used. Mackerel and squid are used for bait. Lightsticks are used. Gear soaks at night.
Fishing Gear and Operational Characteristics • Fiji longline tuna fishery: In 2006 there were 66 longline tuna vessels licensed to fish in Fiji’s EEZ. All of the vessels are domestic Fiji flagged. These vessels are between 14-37 m in length. The fishery operates year-round. Smaller vessels make trips lasting about 9 days, while larger vessels’ trips last about 30 days. The smaller vessels fish at grounds within the Fiji EEZ while larger vessels fish on the high seas and in the EEZs of Vanuatu and the Solomon Islands. Baited hooks are set at depths between 50-300 m. Vessels do not use wire leaders. Vessels use sardine and pilchard for bait. Only larger vessels use lightsticks. Smaller vessels set gear in the early morning and haul in the afternoon. Larger vessels set gear in the morning and haul at night. • Italy Mediterranean industrial longline swordfish fishery: The number of vessels in the Italy Mediterranean industrial longline swordfish fishery is not available. There are 569 Italian demersal and pelagic longline vessels operating in this region. Vessels participating in the Italian Mediterranean largescale swordfish fishery operate from June-October. Trips are between seven and ten days long. Gear is set shallow, with baited hooks no deeper than 60 m. Wire leaders are not used. Vessels primarily use frozen mackerel for bait. Lightsticks are used. Gear soaks at night. • Japan distant water, offshore and nearshore longline fisheries: In 2003 there were 504, 406 and 480 vessels in the distant water, offshore and nearshore longline fleets, respectively. Distant water vessels are > 120 mt, offshore vessels are 10-120 mt, and the smaller nearshore vessels are < 10 mt. All three fleets operate year-round. Distant water vessel fishing grounds range throughout the world’s oceans on trips lasting two to three months. Offshore vessel trips last from one to four weeks, fishing at grounds east of Japan, generally west of 180o longitude. Nearshore vessel trips generally last from one to seven days and are based in coastal waters. Gear design and methods for all fleets vary with targeting strategy. • Peru artisanal longline mahi mahi and shark fisheries: There are as many as 1,500 vessels operating in the fishery. Vessels are about 15 m long. Mahi mahi is the main target species during the austral summer. Sharks are target species from autumn to spring. Fishers target mahi mahi seasonally when this species is abundant in coastal waters. It is more profitable to target mahi mahi at this time of year relative to targeting sharks due to the shorter distance to fishing grounds and shorter trip length, with concomitant reduced costs for fuel and food, but the value of shark meat is usually > than that of mahi mahi. Vessels may travel up to 900 km from shore during the shark season. Mahi mahi trips typically last 5-7 days and shark trips last 15-20 days. Baited hooks are set at depths between 10-16 m. Wire leaders are not typically used during the mahi mahi season but are used during the shark season to maximize shark retention and reduce gear loss. Giant squid, mackerel and flying fish are used for bait. Lightsticks are not used. Gear soaks during the daytime. • South Africa longline swordfish and tuna fishery: There are about 17 South Africa-flagged vessels in this fishery. In 2006 the fishery was divided into two sectors, where permits are now issued separately for vessels targeting tuna or swordfish. The domestic fishery primarily targets swordfish. Vessel lengths range from 19 - 56 m. The fishery operates year-round. Trips last about 14 days. Vessels fish at grounds off the West coast of South Africa mainly on the continental shelf. Hooks are set shallow, seldom deeper than 40 m. Wire leaders are prohibited. Squid is predominantly used for bait, with some fish bait (pilchard and mackerel) mixed in. Lightsticks are usually used. Gear soaks at night. • U.S. Hawaii longline swordfish and tuna fisheries: In 2005 there were 125 active vessels in the Hawaii longline swordfish and tuna fisheries. Vessels are 10-31 m long. The tuna fishery operates year-round. The swordfish fishery is subject to annual turtle and effort caps, causing the fishery to occasionally close before the end of each calendar year. Tuna vessels make trips of about 21 days, fishing at grounds in the Western and central Pacific Ocean. Swordfish vessels make trips of about 30 days, fishing at grounds in the Eastern Pacific and Western and central Pacific Ocean. Tuna vessels set baited hooks at depths between 35-224 m, while swordfish vessels set hooks shallower, between 25-69 m. Most tuna vessels use a wire trace, use fish for bait and are prohibited from using lightsticks. Swordfish vessels do not use a wire trace, use fish for bait (squid is prohibited for use as bait to address sea turtle interactions), and use lightsticks. Tuna gear soaks during the day while swordfish gear soaks at night.
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Page 9 and 10: Contents Summary and Conclusions 1
Page 11 and 12: Contents Appendix 3. Fiji Pelagic L
Page 13: Contents Appendix 8. USA Hawaii Lon
Page 19 and 20: Chapter 1 Introduction and Methods
Page 21: Introduction and Methods 1.2. Metho
Page 25 and 26: Fishing Gear and Operational Charac
Page 27 and 28: Shark Catch Rates and Disposition T
Page 29 and 30: Chapter 4 National and Internationa
Page 31 and 32: National and International Measures
Page 33 and 34: Economic, Practical, Ecological and
Page 35 and 36: Economic, Practical, Ecological and
Page 37 and 38: Chapter 6 Industry Attitudes and Pr
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Page 41 and 42: Industry Attitudes and Practices Fi
Page 43 and 44: Chapter 7 Potential of Deterrents,
Page 45 and 46: Potential of Deterrents, Hotspot Av
Page 47 and 48: References Campana, S.E., L. Marks,
Page 49: References Neves dos Santos, M., Ga
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Appendix 5 Japan Pelagic Longline F
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Japan Pelagic Longline Fisheries Fi
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Appendix 6 Peru Artisanal Mahimahi
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Peru Artisanal Mahimahi And Shark L
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Appendix 7 South Africa Pelagic Lon
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South Africa Pelagic Longline Tuna
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Appendix 8 USA Hawaii-based Pelagic
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Appendix 9 USA Atlantic, Gulf of Me
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Shark Depredation and Unwanted Bycatch in Pelagic Longline

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