Shark Depredation and Unwanted Bycatch in Pelagic Longline

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Shark Depredation and Unwanted Bycatch in Pelagic Longline Fisheries A2.4. Range of Fishing Gear and Methods Fig. A2.1. Bycatch species in the Chilean industrial longline swordfish fishery, 2005 (Barría et al., 2006). fishing areas are in front of Valparaiso and Concepcion at 80°W (Barria et al., 2006). The fishery has been monitored by IFOP since 2001 through the collection of information from shore based and onboard observers. During 2005 the onboard observer program covered 74% of the industrial vessels (Barria et al., 2006). A2.3. The Elasmobranch Fishery The Chondrichthyans fishery has become an important resource for developing countries. Its role increased in terms of food and income generation due to the increasing demand for shark fins, the increase in human population, and the decline in landings of traditional species. Developing countries’ catches increased from 76,000 metric tons (MT) in 1950 to 575,031 MT in 2000 for a value in the year 2000 of $515 million (Cattarci, 2004; FAO, 2006) . Chile has a fishery targeting chondrichthyans. This fishery has increased significantly over the last few decades. Table A2.1 and Fig. A2.2 show the production of elasmobranchs in Chile for the past several decades. The species of chondrichthyans captured for commercial ends in Chile include primarily makos (Isurus oxyrhinchus), blues (Prionace glauca), smoothhounds (Mustelus sp.), yellownose skates (Dipturus chilensis), D. trachyderma, and a holocephali (chimera) known as “pejegallo” (Callorynchus callrynchus) (Sernapesca, 2006). Fig. A2.3 shows the catches of these species of chondrichthyans in Chile from 1990 to 2005 (SERNAPESCA, 2006). For this study we conducted interviews of artisanal longliners in Chile’s northern regions. These vessels target mahi mahi and sharks primarily during the summer months. We also surveyed the industrial swordfish longline fishery where sharks are captured as bycatch. A2.4.1. Artisanal mahi mahi longline This fishery operates in Arica, Iquique, Tocopilla, Antofagasta and Caldera (Barria et al., 2006). Vessels are between 9.1 and 13 meters total length (Barria et al., 2006). They typically work with a surface horizontal longline. Mainline length varies slightly by boat from 2,700 to 3,600 meters. Number of hooks also varies but is typically about 100-350. Mahi mahi season is from December to March. Trip length varies by season with mahi mahi trips typically lasting 3 to 4 days. Almost all vessels use J hooks. Bait species include sardine, mackerel and flying fish (Barria et al., 2006). Total boat crew generally consists of 2 to 3 persons. Gear is set around 7:00 AM and hauled at 4:00 or 5:00 PM (Barria et al. 2006 and present surveys). Weighted swivels and steel leaders are used during the shark season. Table A2.2 provides a comparison of artisanal mahi mahi gear with industrial longline swordfish gear. A2.4.2. Industrial swordfish fishery This fishery mainly uses the American longline configuration (12 of 16 vessels) but several vessels use the Spanish configuration. The following information on gear characterization for both configurations was taken from Barria et al. (2006). See Table A2.2 and Figs. A2.4 and A2.5 for a comparison of longline gear configurations. The Spanish configuration includes a mainline of braided polypropylene rope. The mainline is divided into 110 hooks sections. Each of these sections has a radio beacon buoy at its beginning and end. Every 23 fathoms there is a branchline with a hook, and each branchline is knotted to the mainline. A buoy is placed every 10 branchlines. Branchlines are 4.5 fathoms long. Leaders are made of polypropylene but also has a portion made of metal cable (1.5 mm diameter). This cable adds weight to the line and is better able to retain sharks. Vessels usually deploy a 45 nautical mile long mainline containing approximately 2,000 hooks. The Spanish system does not allow for variation in the depth of the hooks. These vessels also use photoactive plastic polymer balls that glow after being exposed to light. Each hook has four of these. Spanish and Chilean mackerel and squid (Ilex argentinus) are used for bait. The American configuration has a monofilament mainline. In this system the mainline is divided into sections of 220-250 hooks with a radio beacon buoy at the beginning and end. The mainline usually has a total of 7 beacon buoys and 1500 (range of 1200-2000) hooks. Distance between hooks and depth of hooks can be modified. Every 5 hooks there is a float buoy. As the distance between hooks is increased, the maximum depth of the hooks increases as does the total mainline length. Mainline length ranges from 35 to 55 nautical miles. The American configuration uses lights in the weighted swivel (65-75g.). These may be chemical or battery powered. Light are green or violet. Branchlines may be 6 to 18 meters long and have a 15-20 cm cable leader. This system uses a timer for setting of hooks 1 All prices are given in U.S. dollars unless otherwise indicated 56
Chile Artisanal Mahimahi and Shark Longline Fishery and Longline Swordfish Fishery Table A2.1. Catch of the main shark species in Chile, 1991-1996 (SERNAPESCA, 2006; Vanuccini, 1999). Species 1991 1992 1993 1994 1995 1996 Rays 1,171 1,239 1,971 2,899 2,622 2,67 Makos 1,118 702 581 450 475 320 Smoothhounds 937 481 398 588 193 225 Blues 212 175 237 33 39 11 Total 3,438 2,597 3,187 3,970 3,329 3,235 Fig. A2.2. Total elasmobranch production in Chile, by species groups, 1950- 2004 (FAO, 2006). Fig. A2.3. Catch of chondrichthyans in Chile, 1990 - 2005 (SERNAPESCA, 2006). (8 to 16 seconds). Bait used is squid and Chilean mackerel. Bait is usually hooked through the eye but may also be hooked in the back or tail. The American configuration generally operates more cleanly (less bycatch) than the Spanish system. Table A2.2 and Fig. A2.4 and A2.5 summarize the general fishing methods and gear deployment strategies for the longline for mahi mahi and swordfish in the ports where surveys were conducted. It should be noted, however, that fishing methods and gear deployment vary somewhat from port to port and vessel to vessel. A2.5. Catch and Discard Rates of Target and Bycatch Species A summary of shark yield for the artisanal longline shark fishery from 2003-2005 is presented in Table A2.3 A summary of swordfish captures, effort and yield for the industrial and artisanal swordfish fleets during 2004 and 2005 is presented in Table A2.4. During the 2005 season of the industrial swordfish fishery, almost all sharks captured were retained and commercialized (Table A2.5). Total fleet effort for 2005 consisted of 2.16 million hooks. A2.6. Regulations and Management Framework Fisheries regulations are formulated by the Fisheries Sub Secretary (SUBPESCA). Implementation and monitoring of regulations is conducted by SERNAPESCA. Ley General de Pesca y Acuicultura (1991) established a number of regulations for industrial and artisanal fisheries. The most important of these is the proportional distribution of total captures to industrial vessel owners (a maximum capture limit per owner). SUBPESCA has also established maximum quotas by fishing season and by Regions and has suspended new authorizations of industrial vessels. Chile has a National Plan of Action for Sharks that addresses most of these regulations and promote the establishment of other, new regulations. These proposed regulations would address issues such as bycatch monitoring and assessment (SERNAPESCA, 2006a). 57
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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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Page 19 and 20: Chapter 1 Introduction and Methods
Page 21 and 22: Introduction and Methods 1.2. Metho
Page 23 and 24: Fishing Gear and Operational Charac
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
Page 39 and 40: Industry Attitudes and Practices Lo
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
Page 52 and 53: Shark Depredation and Unwanted Byca
Page 99 and 100: Appendix 5 Japan Pelagic Longline F
Page 101 and 102: Japan Pelagic Longline Fisheries Fi
Page 103 and 104: Japan Pelagic Longline Fisheries mo
Page 105 and 106: Japan Pelagic Longline Fisheries Ta
Page 107 and 108: Japan Pelagic Longline Fisheries is
Page 109 and 110: Japan Pelagic Longline Fisheries ta
Page 111 and 112: Japan Pelagic Longline Fisheries In
Page 113 and 114: Japan Pelagic Longline Fisheries A5
Page 115 and 116: Appendix 6 Peru Artisanal Mahimahi
Page 117 and 118: Peru Artisanal Mahimahi And Shark L
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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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USA Hawaii-based Pelagic Longline S
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Appendix 9 USA Atlantic, Gulf of Me
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USA Atlantic, Gulf of Mexico and Ca
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Shark Depredation and Unwanted Bycatch in Pelagic Longline

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