Shark Depredation and Unwanted Bycatch in Pelagic Longline

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Shark Depredation and Unwanted Bycatch in Pelagic Longline Fisheries deeper setting fisheries. Gear designs are extremely variable between fisheries, as well as from seaport to seaport, by season and fishing ground within a fishery, between vessels within a fishery, and for some parameters, within the gear of an individual vessel. Incentives to reduce shark interactions in pelagic longline fisheries vary along a continuum, based on whether sharks represent an economic disadvantage or advantage. On one extreme, there are pelagic longline fisheries with a regulatory framework limiting shark catches or placing restrictions on shark handling, or lack of markets for shark products, resulting in negligible retention of sharks. In these fisheries, the costs from shark interactions exceed benefits from revenue from sharks, due to: (i) Depredation; (ii) Damage and loss of gear; (iii) Reduced catch of marketable species due to baited hooks being occupied or removed by sharks; (iv) Risk of crew injury from handling caught sharks and being hit by weights when branch lines containing sharks break during gear retrieval; and (v) Reduced fishing efficiency due to the time required to remove sharks from gear for discarding and to repair and replace gear. Fishers identified the time required to repair damaged and lost gear from shark interactions, and to remove sharks to be discarded from gear, as a substantial problem. Lost revenue from shark damage to target species can amount to several thousand U.S. dollars in a single set in some fisheries. In some of these fisheries, there is large interest in minimizing shark interactions. On the other extreme, there are pelagic longline fisheries where revenue from sharks exceeds costs from shark interactions, a large proportion of caught sharks are retained (> 99% in some fisheries), and sharks are either always an important target species, are targeted seasonally or at certain fishing grounds proximate to ports where there is demand for shark products, or are an important incidental catch species. Several nations, including half of the countries covered in this study (Australia, Italy, South Africa, and U.S.A.), have legally binding prohibitions in effect on the removal of shark fins (including the tail) and discarding of the remainder of the shark at sea in their pelagic longline fisheries. Some of the longline fisheries included in this study are subject to prohibitions on the use of wire leaders (Australia, South Africa), have shark retention trip limits (Australia, South Africa), and have size limits for certain shark species (Peru). Fishers in the Italian sector of the Mediterranean industrial longline swordfish fishery are unaware of the finning restriction, and thus the legislation does not affect their practices. However, no shark finning is reported to occur in the fishery due to the lack of a local market for the fins. In the fisheries in Australia, South Africa, and Hawaii, U.S.A., finning restrictions have substantially reduced shark retention, most captured sharks are now discarded alive, while revenue from sharks has been substantially reduced. Japanese longline fishermen in the distant water fleet have adapted to finning regulations applicable in some areas by landing sharks in recently developed local markets rather than by attempting to avoid shark interactions. In waters without finning regulations, including Japanese waters and the North Pacific, sharks are either finned or landed whole, and in either case the ability to sell shark products has contributed to a lack of interest in reducing shark bycatch. A trip limit on the retention of shark carcasses in Australia has likely had no effect on industry practices, as vessels typically will not reach the per-trip limit for shark species that are worth retaining. A shark per-trip retention limit in South Africa may have a large adverse economic effect; however, there may be low compliance. A shark size limit in effect in the Peru longline fishery is not strongly enforced, and few fishers are aware of the rule. Of the few fishers who reported that they were aware of the regulations, all report that they still retain sharks that are under the minimum size limit. A prohibition on the use of a wire trace in the Australia and South Africa longline fisheries has resulted in an increased economic cost from shark interactions from an increase in lost terminal tackle. In fisheries where most sharks are released alive, it is not known how the injury to sharks from retaining hook and trailing monofilament line affects their survival prospects compared to being caught on lines with wire trace. In fisheries where a large proportion of caught sharks are killed either for retention or discarding, prohibiting wire leaders will likely reduce shark fishing mortality. Prohibiting wire leaders may exacerbate seabird bycatch problems: Fishers will be less likely to attach weights close to hooks on branch lines lacking a wire leader due to safety concerns, thus, reducing the baited hook sink rate, and increasing seabird catch rates. In fisheries where there is an incentive to avoid shark interactions, predominant shark avoidance practices are to: (i) Avoid fishing in areas known to have high shark interactions; and (ii) Change fishing grounds when shark catch rates, depredation and gear loss are high but the target species catch rate is low. Some fishers indicate that using fish instead of squid for bait reduces shark interactions. Experimental trials have shown that using fish instead of squid as bait results in a significant and large decrease in shark catch rates. However, results of trials of different hook types are less conclusive, with some studies showing small but significant increases in shark catch rates with a circle hook, and other studies indicating no difference between circle and other hooks. Longline fishers identified numerous fishing methods and gear characteristics that they conventionally employ to maximize catch rates of non-shark target species, which may contribute to reducing shark catch rates. For instance, the depth of baited hooks; timing of gear setting, soak and hauling; location of fishing grounds in relation to topographic and oceanographic features (e.g., position with regard to oceanic fronts); type and size of bait and hook; leader material; non-use of lightsticks; and other fishing methods and gear designs selected by fishermen to maximize their non-shark target species catch rates may be effective shark avoidance strategies. Research is needed to improve the understanding of the shark avoidance efficacy of these practices. Beyond these strategies, the state of knowledge to reduce unwanted bycatch and depredation by sharks in pelagic longline fisheries is poor. A prioritized next step is to test promising, new strategies
Summary and Conclusion to reduce unwanted shark bycatch, depredation and gear damage in pelagic longline fisheries. Shark deterrents that hold promise include chemical, magnetic, electropositive rare earth metals, and electrical deterrents. Some of these strategies are concepts requiring substantial investment to develop the technology for application in longline gear. Research and commercial demonstrations are needed to assess effects of these deterrents on catch rates of sharks, target and incidental species. Fleet communication programs can enable a longline fleet to avoid shark hotspots. The distribution of sharks in some fishing grounds is often unpredictable, and may be spatially contagious or aggregated. Consequently, fleet communication systems may be employed by fishing industry to report near real-time observations of hotspots to enable a fishery to coordinate operations to substantially reduce fleet-wide depredation and bycatch of sharks. In addition, fleet coordination of daily fishing positions and times, a current practice in many nations’ fleets, may minimize per vessel shark depredation and catch levels relative to vessels that fish in isolation. Such techniques will only be of interest in fisheries where shark interactions pose a substantial economic disadvantage. These shark avoidance strategies promise to benefit shark populations as well as those fisheries where shark interactions are an economic disadvantage. market continues to grow, this will likely lead to a rapid increase in shark catch rates and fishing mortality. This study shows that fishers possess the knowledge to modify their fishing gear and methods to maximize shark catch. Sharks are particularly vulnerable to overexploitation and slow to recover from large population declines. The expanding exploitation of sharks, for their fins as well as meat, warrants concern for the health of shark populations as well as ecosystem-level effects from population declines. This is compounded by the absence of effective management frameworks in most fisheries, in combination with the lack of both reliable fishery-dependent data and fundamental biological information for most shark species. Of the 12 fisheries included in this study, only two are subject to shark retention trip limits, while five have no measures to manage shark interactions. Thus, to prepare for a possible increase in demand for shark meat, in areas where sharks are target species or could become targets, fishery management authorities are encouraged to begin effective data collection, monitoring and precautionary shark management measures to ensure that shark fishing mortality levels are sustainable. A large proportion of pelagic shark species are alive when gear is retrieved. Reducing gear soak time would increase the proportion of caught sharks that are alive when hauled to the vessel. In longline fisheries where information is available, most sharks that are alive when hauled to the vessel and will be discarded are released alive. When a caught shark is discarded, fishers indicate that most of the time they will either cut branch lines, cut the hook out of the shark’s mouth or pull the hook out by force in order to retrieve the terminal tackle before discarding the shark. It is uncommon for fishers to kill a shark to retrieve terminal tackle or to prevent future shark interactions. Most fishers perceive commercially available de-hooker devices to be impractical and potentially dangerous for use with sharks. While available information indicates that a large proportion of sharks caught in longline gear that are released after removal of the hook will survive, and while many fishers do not see a need for new hook removal methods, development of especially designed equipment to discard sharks could improve shark post release survival prospects, reduce the loss of terminal tackle and improve crew safety. In fisheries where shark finning occurs, to avoid injury and increase efficiency, crew first kill the fish before removing fins, and do not remove fins from live sharks. A recent trend of expanding demand for shark meat at several ports worldwide is creating a shift in utilization of shark meat in some fisheries. In these fisheries, there is increased incentive to target and catch sharks. Given the increasing globalization of fish markets, this trend could spread to other fisheries where currently there are no markets for shark meat. This trend toward more utilization of shark meat may be beneficial in the short term in that fully utilized sharks are more likely to be reported in logbooks and landings statistics than are the retention and landing of just fins. However, if the shark meat
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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 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
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Appendix 5 Japan Pelagic Longline F
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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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