Shark Depredation and Unwanted Bycatch in Pelagic Longline

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Shark Depredation and Unwanted Bycatch in Pelagic Longline Fisheries A2.14.5. Reducing the attractiveness of baited hooks to sharks, such as by using artificial baits, using or not using light sticks, or avoiding a bait type known to result in high shark catch rates Over a quarter (26.3%) of mahi mahi fishermen believe that avoiding bait types known to result in high shark catch rates would reduce shark interactions. About two thirds (63%) of respondents replied that these strategies would not be effective. Of these, two fishermen (16.7%) replied that shark interactions occur even when not using bait types typically employed for shark capture. Three respondents (25%) believe artificial bait would not be economically viable for mahi mahi capture since bait type for this target species is captured fresh before the setting of the longline. Two of three swordfish fishermen replied that they believe these strategies would reduce shark captures. A2.14.6. Reducing injury to hooked sharks that you will discard Almost a quarter (25.1%) of all respondents with mahi mahi as target species reported discarding small sharks alive. Of these, three quarters (75%) did not indicate a way to reduce injury to hooked sharks that they will discard, while the remainder replied that the use of dehookers will not reduce injury to hooked sharks for discarding. One respondent (5.3%) mentioned that he uses a dehooker to recover hooks from sharks when these are on board and already dead. No swordfish fishermen reported discarding sharks alive. However, one of them said that they would discard blue sharks due low storage capacity. It is unclear whether or not they fin those sharks before discarding. A2.14.7. Reducing shark retention by avoiding a specific size or type of hook, or by not using wire leaders on branch lines Of mahi mahi fishemen, only one respondent (5.3%) replied that the size of the hook would affect the shark catch rate. About 36.8% (among whom there were fishermen that use both nylon and wire leaders) replied that shark retention is or would be reduced by not using a wire leader on their branch lines. Three fishermen (15.7%) that use wire leaders believe that using nylon monofilament would mean an increase in gear loss from sharks. Some respondents use nylon monofilament only because they believe that using wire leaders would decrease their target species capture during the summer. Wire leaders are used during shark season to increase shark capture. Two swordfish fishermen indicated that not using wire leaders will reduce shark retention. A2.14.8. Will the economic impact of sharks be reduced from using a wire leader on branch lines Most respondents (73.7%) that fish for mahi mahi believe that the economic impact of sharks is or would be reduced by using a wire leader on branch lines. Among those respondents were all of the ones that use wire leaders and two thirds of fishermen that use nylon monofilament. One of the latter stated that he will not switch to wire leader because it would reduce his target species capture. However, another fisherman that use wire leaders mentioned that target species capture remains the same as if using nylon monofilament. All three swordfish fishermen interviewed believe that the cost from damage to gear is or would be reduced by using wire traces on branch lines. A2.14.9. Most important factor that affects shark CPUE Over two thirds (68%) of mahi mahi fishermen believe that altering fishing position in relation to certain water temperatures alone will result in a high shark catch rate. The other third (32%) replied that a combination of different factors results in a high shark catch rate. Half of these respondents did not specify these factors. Equal amount of respondents replied (1) that altering fishing position and setting gear deeper will increase shark CPUE, (2) that time of month was an important factor along with altering fishing position in shark capture, or (3) that it is certain water temperatures together with time of the day that are the most important factors affecting shark CPUE. Respondents based their answer on their fishing practices during shark season. According to all swordfish fishermen, it is a combination of different factors that will affect shark CPUE, but they did not specify these factors. A2.15. Incentives and Attitudes on Reducing Shark Bycatch and Depredation In general, both swordfish and mahi mahi fishermen interviewed (95%) are not interested in reducing shark bycatch. Forty-seven percent and 33.3% of mahi mahi and swordfish fishermen, respectively, are interested in reducing shark depredation. The most common reason given by mahi mahi fishermen for not wanting to reduce shark interactions is because of the high value for shark meat and fins. Swordfish fishermen also mentioned that they do not want to avoid catching shark because it is profitable. Only one fisherman from a swordfish vessel replied that he wants to avoid shark interactions because they are not his target species. Over two thirds (68.4%) of respondents believe, in the absence of restrictions on finning sharks, that bycatch during mahi mahi season would not mean a decline of shark populations. Two mahi mahi fishermen (9.1%) replied that shark bycatch during summer time is not high enough to threaten shark populations. Another two fishermen blamed industrial vessels for declines in shark populations due to finning aboard these vessels. About 72% of respondents stated that their general feelings about sharks are that they are economically important. For them, sharks mean mostly extra income. One swordfish fisherman (4.5% of respondents) mentioned that it is sometimes annoying having many sharks in the line. Six (27.3%) respondents stated that sharks should be under sustainable management program. They believe shark populations have declined within the past years and that penalties, bans, and more control over industrial vessels should be enforced for conservation purposes. A2.16. Supporting Figures Figs. A2.8 – A2.16 provide images of the fisheries described in this contribution. 64
Chile Artisanal Mahimahi and Shark Longline Fishery and Longline Swordfish Fishery Fig. A2.8. A typical artisanal mahimahi longline vessel from the port of Arica in northern Chile. Fig. A2.9 An artisanal longline vessel in Arica using a monofilament mainline. Fig. A2.10. Fisherman demonstrating an improvised de-hooker. Fig A2.11. Multifilament mainline and hooks in stern of artisanal longline vessel. Fig A2.12. Sample of J hook and leader used by artisanal vessels in Chile Fig. A2.13. Artisanal mahi mahi longliners in the port of Iquique. Fig. A2.14. J hooks aligned in storage rack of artisanal longliner for mahi mahi, Iquique. 65
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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
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
Page 127 and 128: 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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