Shark Depredation and Unwanted Bycatch in Pelagic Longline

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Shark Depredation and Unwanted Bycatch in Pelagic Longline Fisheries A8.11.5. 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 A quarter of respondents believe that artificial bait holds promise to reduce shark interactions, but research is needed to find a product that is effective at catching target species. Over half of the respondents replied that they do not know if these strategies would be effective, but that they would have to be economically viable and not reduce target species CPUE. A minority of respondents (2, 17%) believe that these strategies would not be effective. A longline swordfish captain explained that he catches sharks at equal rates on hook with and without lightsticks, so he does not believe that refraining from using lightsticks will affect shark catch rates or depredation. Fig. A8.3. Blue shark CPUE (fish per 1000 hooks) by area for Hawaii-based longline vessels setting gear shallow to target swordfish and yellowfin tuna, 1998 (Ito and Machado, 1999). A8.11.6. Reducing injury to hooked sharks that you will discard Most respondents believe that sharks that are discarded by cutting the branch line or cutting their mouth to remove the hook are not injured to a degree that it will result in their eventual mortality. Several fishers replied that they would not want to bring sharks closer to the vessel than their current practice because this would increase the risk of the swivels hitting the crew if the line breaks; About two thirds of caught sharks are discarded by cutting the branch line. Two fishers that report using a ‘shark line’ to temporally hold branch lines containing caught sharks when they are too busy processing fish on deck to remove the gear from the sharks replied that discontinuing this practice would reduce the mortality of caught sharks. All respondents replied that dehookers would increase the risk of injury to crew, are not effective due to the way many sharks roll when being handled, and could result in increased injury to the shark if they bite on the dehooker while spinning. A8.11.3. Limiting shark access to baited hooks, such as altering fishing practices to consider deployment depth of hooks and timing of the soak and haul to avoid problematic shark species Half of the respondents believe that it is possible to reduce shark interactions by setting baited hooks deeper. Two of the longline tuna captains explained that while they believe it is possible to reduce shark catch by setting gear deeper, they would not do this because it would reduce their catch rate of target species, and because their catch of sharks is not typically problematic. None of the respondents believe that altering the timing of fishing operations would affect their shark catch rate. A8.11.4. Deterring sharks such as with chemical shark deterrents and electrical deterrents A third of respondents believe that deterrents such as chemical compounds and electrical currents will not be effective at reducing shark bycatch and depredation, while two thirds replied that they do not know if they would be effective. One respondent believes that these types of deterrents won’t work if sharks are in a feeding frenzy. Several respondents explained that they would want to know research results on the effect of these strategies on target species CPUE. Two respondents explained that the cost of the deterrent would have to be sufficiently low for them to use it because shark catch and depredation is typically not a large economic problem. A8.11.7. Reducing shark retention by avoiding a specific size or type of hook, or by not using wire leaders on branch lines Two thirds of respondents do not believe that the design or size of the hook would affect the shark catch rate. Most respondents replied that shark retention would be reduced by not using a wire leader on their branch lines. The two interviewed captains (one longline tuna and one longline swordfish captain) who do not use wire leaders on their branch lines replied that they would not want to switch to using a wire leader because they believe it would decrease their target species CPUE. The ten fishers (from longline tuna vessels) who use wire leaders replied that they would not want to eliminate use of the wire leader because this would reduce their tuna CPUE and would increase the risk of injury to crew from being hit by swivels if lines break during hauling. A8.11.8. Will the economic impact of sharks be reduced from using a wire leader on branch lines None of the respondents would be willing to change their current gear design to add or remove a wire leader in order to change the retention of caught sharks on the gear because they believe that this change would result in a net economic cost by reducing target species CPUE. Most respondents replied that the cost from damage to gear would only be slightly reduced by using vs. not using a wire leader on branch lines, as more terminal tackle could potentially be saved when sharks are caught on branch lines with wire leaders. 130
USA Hawaii-based Pelagic Longline Swordfish and Tuna Fisheries A8.11.9. What is the most important factor that affects shark CPUE - altering fishing position in relation to certain water temperature, topographic features, or oceanographic features; changing the time of day or month of setting or hauling; changing the depth of hooks, or a combination of these factors? Most respondents believe that the shallower their gear, the closer the fishing gear is to topographic features such as seamounts and shelf breaks, and proximity to oceanographic fronts are the three most important variables that will result in a high shark catch rate. A longline swordfish captain believes that shark abundance will be higher on the colder side of fronts while three longline tuna captains believe that certain species of sharks will be more abundant on the warm side of fronts. Time of day, month, and year were not considered to be important factors determining shark capture. A8.12. Incentives and Attitudes on Reducing Shark Bycatch and Depredation In general, both captains and crew in the Hawaii pelagic longline swordfish and tuna fisheries are interested in reducing shark bycatch and depredation as long as the method employed to achieve this does not also reduce their catch rate of commercially valuable species. The four most common reasons identified for wanting to reduce shark interactions are to (i) reduce the time required to discard caught sharks, (ii) reduce the time and expense of replacing and repairing lost and damaged gear, (iii) reduce lost revenue from damaged target and incidental catch, and (iv) reduce the risk of injuring crew from being hit by weighted swivels when branch line break during hauling. Most (two thirds) of respondents stated that they wish to reduce catch rates of sharks in order to reduce the loss of revenue, where the capture of every shark is one less hook available to catch a target species. A few respondents clarified that that they want to avoid catching sharks because most shark species have no economic value and the two species that can be sold are worth relatively very little. Only one respondent believes, in the absence of restrictions on finning sharks, that fishing mortality would result in the decline of shark populations or that overfishing would occur. Most (75%) of the respondents stated that their general feelings about sharks are that they are a ‘nuisance’ and that they wish they could avoid them. Many respondents see shark depredation, requiring time to remove sharks from hooks, damaging and losing gear, and damaging and losing caught fish, as an expected and unavoidable part of longline fishing. A few respondents believe that sharks are more than just a nuisance, as shark interactions reduce the viability of their livelihood. This is generally consistent with the results reported by McCoy and Ishihara (1999). Two fishers indicated that they see sharks as an apex predator at the top of the marine food chain, and as such, sharks play an important role in maintaining the natural functioning of the ocean ecosystem. One respondent sees sharks as a renewable natural resource, which should be managed for optimal yield just like other commercial marine fish, and that fishers should be able to fin them under a sustainable management regime. A8.13. References Boggs, C. 1992. Depth, capture time, and hooked longevity of longlinecaught pelagic fish: Timing bites of fish with chips. Fishery Bulletin 90(4): 642-658. Bolten, A., Bjorndal, K., 2002. Experiment to Evaluate Gear Modification on Rates of Sea Turtle Bycatch in the Swordfish Longline Fishery in the Azores. Final Project Report submitted to the U.S. National Marine Fisheries Service. Archie Carr Center for Sea Turtle Research, University of Florida, Gainesville, Florida, USA. Brothers, N., E. Gilman. 2006. Technical Assistance for Hawaii Pelagic Longline Vessels to Change Deck Design and Fishing Practices to Side Set. Hawaii Longline Association, U.S. NOAA Fisheries Pacific Islands Fisheries Science Center and Pacific Islands Regional Office, and Western Pacific Regional Fishery Management Council: Honolulu, Hawaii. Clemens, A. 2006. Annual Report on Seabird Interactions and Mitigation Efforts in the Hawaii Longline Fishery for Calendar Year 2005. Administrative Report AR-PIR-04-06. U.S. National Marine Fisheries Service, Pacific Islands Regional Office, Honolulu, HI, USA. Gilman, E., D. Kobayashi, T. Swenarton, P. Dalzell, I. Kinan, N. Brothers. 2006a. Efficacy and Commercial Viability of Regulations Designed to Reduce Sea Turtle Interactions in the Hawaii-Based Longline Swordfish Fishery. Western Pacific Regional Fishery Management Council, Honolulu, HI, USA. ISBN 1-934061-02-6. Gilman, E, Zollett, E., Beverly, S., Nakano, H., Shiode, D., Davis, K., Dalzell, P., Kinan, I., 2006b. Reducing sea turtle bycatch in pelagic longline gear. Fish and Fisheries 7(1): 2-23. Hamilton, M., R. Curtis, M. Travis. 1996. Cost-earnings Study of the Hawaiibased Domestic Longline Fleet. JIMAR Contribution 96-300. Joint Institute for Marine and Atmospheric Research, Honolulu, Hawaii, USA, 59 pp. Ito, R., Machado, W. 2001. Annual Report of the Hawaii-based Longline Fishery for 2000. U.S. National Marine Fisheries Service Southwest Fisheries Science Center, Honolulu Administrative Report H-01-07, Honolulu, HI, USA. Ito, R., Machado, W. 1999. Annual Report of the Hawaii-based Longline Fishery for 1998. U.S. National Marine Fisheries Service Southwest Fisheries Science Center, Honolulu Administrative Report H-99-06, Honolulu, HI, USA. McCoy, M., H. Ishihara. 1999. The Socioeconomic Importance of Sharks in the U.S. Flag Areas of the Western and Central Pacific. Gillett, Preston and Associates, Inc., Honolulu, Hawaii, USA, and U.S. National Marine Fisheries Service Southwest Region Administrative Report AR-SWR-00- 01, La Jolla, CA, USA. 117 pp. Pacific Ocean Producers. 2005. Pacific Ocean Producers Commercial Fishing and Marine Supplies for the Asia-Pacific Region Catalog 2004-2005. Pacific Ocean Producers, Honolulu, Hawaii, USA. U.S. National Marine Fisheries Service. 2005b. 2005 Report to Congress Pursuant to the Shark Finning Prohibition Act of 2000 (Public Law 106-557). U.S. National Oceanic and Atmospheric Administration, U.S. Department of Commerce, Washington, D.C. 52 pp. 131
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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 115 and 116: Appendix 6 Peru Artisanal Mahimahi
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Shark Depredation and Unwanted Bycatch in Pelagic Longline

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