Shark Depredation and Unwanted Bycatch in Pelagic Longline

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Shark Depredation and Unwanted Bycatch in Pelagic Longline Fisheries From late 2005 vessels specifically altering fishing strategy to target fish at greater depth have reported a corresponding decline in catch rates of non-target species, including sharks. So far, this change in fishing strategy is not widespread. A1.9.3. Bait type Perhaps not so common elsewhere in pelagic longline fisheries is the widespread dependence on baiting hooks with live fish in Australia. The catch rates of sharks when using conventional thawed bait compared to when using live bait has not been evaluated, although respondents to the shark survey with live bait experience gave a mixed response to the question. When squid is used for bait, light sticks are generally also used. Respondents to the shark survey (survey section) gave mixed response to both questions relating to shark catch on lights sticks and to bait type but were not questioned on bait type specifically with or without a light stick. Weight of opinion was however toward squid and light sticks exacerbating shark catches. If observer records from 402 sets by vessels that used light sticks are any indication, the number deployed is high, with an average of 605 per set. But from the records the overall percentage of sets in which light sticks are used is unclear. A1.9.4. Line weighting The AFMA observer database of line weighting characteristics in this fishery suggest that, unless the presence of a weight went unrecorded, most vessels do not use any branchline weight. In a 47 vessel sample, 15 used weight, either 38g or 60g with 2 using 100g at an average distance away from the hook of 4.7 m. As previously mentioned, line setting depth (and therefore perhaps shark catch reduction potential) may increase when lines are more heavily weighted in an effort to reduce seabird mortalities (DEH 2005). A1.9.5. Method used to dispatch captured fish Contrary to perhaps the majority of the worlds’ pelagic longline fisheries, Australian operators mostly utilize the legal prerogative of firearms to kill captured fish once these are alongside the vessel. Effective, arguably more humane and beneficial to product quality, this method of dispatch is likely to be increasing the number of sharks that are killed and kept, are killed to recover the hook and then discarded or, simply killed for no specific reason other than an aversion to discarding any sharks alive. Without firearms, and taking into account potential time wasted and safety issues, the best option is discarding. In fact, few operators except some of those that use firearms consider handling live sharks viable from a safety and economic perspective. A1.9.6. Hook type Consistent with the trend in pelagic longline fisheries elsewhere, there is recent interest in assessing the consequence of a change to circle hooks on species catch and survival rates in Australia. Most recent data on hook type usage are from only 23 vessels, 20 of which were using ‘J’ hooks of various sizes, two were using circle hooks and one vessel had a mix of both types. It will be some time therefore before any conclusive evidence may emerge in relation to hook type performance in this fishery. Although there has been some evidence that circle hooks may actually catch more sharks (Ward et al., 2005), fish caught on circle hooks are likely to be less damaged by the hook, (Falterman et al., 2002; Watson et al., 2005). A1.10. Survey of Shark Fishing Practices, Handling Strategies, and Fishers’ Opinions of Sharks and Shark Management A1.10.1. Methods Between 1 January and 16 February 2006, nine fishing ports scattered throughout the entire latitudinal extent of the east coast pelagic longline fishery were visited with the objective of conducting interviews with individual fishers and fleet managers. Because shark bycatch can be a controversial and sensitive issue for fishers to discuss, input of a meaningful nature to the survey was generally sought from those in the industry with a prior reliably cooperative record. Whilst not all those interviewed were still actually fishing, all had done so while the most recent shark-specific management conditions have applied. Interviews were conducted individually and the duration required was generally from 60 to 90 minutes. Initially the survey comprised 62 questions but was progressively modified to be more relevant, appropriate and comprehensive with consideration to information provided by the respondents. Answers have been provided for 49 of these questions. Of those interviewed, three were fleet owner/managers and one was an owner/manager who also fishes. These interviewees combined, control 1/3 of all vessels in the fishery. Eight others interviewed were owner/operators and a further two worked on vessels that they did not own. Although confidentiality in relation to participation was offered, all respondents had no hesitation in indicating that this was not necessary. To be expected in a survey of this nature, much useful, relevant information not canvassed, was forthcoming. Much of this additional information has been incorporated into the results of the survey. As a means of putting the practicalities of the Australian longline fishery into world context, a profile of the Australian vessels and their methods of operation was constructed. Because no such summary of current fleet characteristics seems to have been previously collated, information was sought from the AFMA observer database (Table A1.1) of vessel, gear and fishing activity throughout 2005. Data of this nature over a longer time interval were not considered indicative of current gear and/or operational characteristics because these have changed in response to recent regulatory requirements. The operational and gear characteristics were considered in relation to their potential effect on shark catch rate and handling practices. Also undertaken, was a review to put pelagic Australian longline fishery shark catches and utilisation into perspective with consideration to other fisheries, management means and measures. A1.10.2. Survey results It was obvious that the attitude to sharks both in terms of economic incentive to utilize or not, was somewhat dictated by latitudinal change in species presence, their abundance and how this alters the extent of negative economic consequences from gear and target species destruction. Sharks caught by pelagic longline fishing in Australia fall into three categories of economic relevance to operators: to some they are considered equal component of target species catch composition: to others they are treated as by-product only and largely as a consequence of logistics (tending to mostly land and 46
Australia Longline Tuna and Billfish Fishery retain individuals in already dead or near-so condition). The third category into which sharks that are caught fall is that of bycatch whereby operators have no inclination to retain any, and take the safest and quickest means of discarding them. However, all or most survey respondents agreed that their attitude to the sharks that they catch is largely a financial consideration, in that if it was economically worthwhile with established markets and unrestricting regulations, sharks would become a bycatch species of importance to the extent that some operators would actually target them more with appropriate gear changes. Regardless, most respondents were of the opinion that shark-specific regulations have had little or no impact on the nature of and extent of their interactions with sharks. This is because they would seldom have the opportunity to exceed the existing 20 shark per trip retention limit of species that are of sufficient value to make retention worthwhile (unless those species with little or no market value were to become economically attractive to retain). In Australia it would seem that the shark-specific management prescriptions, particularly those of finning and a per-trip retention limit has altered the way in which sharks are handled by 50% of operators, but the regulations do not preclude routine killing of the sharks that are caught. Also, irrespective of the current attitude to finning, historical data do suggest that without specific regulations preventing this, sharks would be killed for their fins alone by many operators. using wire. For example, operators become proficient at retaining all their fishing gear when a shark is caught because the wire from the hook to a 45g or 60g swivel (about 600mm or less away), allows for greater control with much improved safety. (Wire is more likely to not part from the fish under tension and being less elastic (compared to nylon under tension) is not so dangerous). Thus, sharks are generally released in good health alongside the vessel with the fishing gear recovered and un-damaged. Also in parts of Australia the daily gear damage because wire cannot be used is considered economically and/ or operationally unacceptable. But one reason given for a preference not to use wire, if free to do so was that shark handling time and increased difficulties in discarding sharks are unacceptable. Half the respondents do not consider any effort to retain sharks or recover the gear (hook) from sharks is worth it because economic loss from this will always exceed the little revenue derived from retention of sharks. (Table A1.4) (Aside from the associated risks to crew from handling sharks). In fact, potential injury to crew (less of a consideration if firearms are used to kill fish) was an important consideration dictating the fate of sharks caught. Table A1.4 . Summary of opinions expressed by survey respondents on how to minimize or increase shark catches. In the Australian fishery, where an accepted and widespread method used to kill fish is with a firearm, most operators were of the opinion that this practice alone can result in the death of significantly more sharks that are not in any way utilized. Several operators, whilst personally disinclined to do so, indicated that other operators do kill all sharks, if only to safely recover hooks that are otherwise lost as each shark is cut free. But on many vessels, (over 1/3 of the fleet) the safety concerns associated with firearms aboard outweigh any perceived safety or operational advantages of firearms use (57% of respondents). Strategy Set on the cold side of a thermocline Light stick use (esp blue) Intermediate mainline floats Circle hooks (mouth hook only) Live bait use Fewer Sharks X X X More Sharks X X Of the respondents, over half would elect to use wire traces to some degree if free to do so (use of wire traces is not permitted in the fishery). Reasons for this preference varied from this being considered a necessity in lower latitudes owing to: Set hooks deeper Talk to other vessels Larger bait size X X X • The extent of gear damage and therefore lost fishing efficiency caused by sharks, lancetfish, snake mackerel and marlin, if wire is not used; and • The fact that sharks here are an economically viable target catch. More oily bait (pilchards) Use wire trace Discharge burley during set X X (maybe) Elsewhere, operators considered that intermittent wire use could deliberately allow for capture of a specific individual shark (as opposed to it being able to bite through a nylon trace), which would otherwise cause considerable economic loss by biting off hooks or destroying, caught target fish. Several respondents were of the opinion that if wire use was widespread, then with more sharks caught, larger numbers in total would die. It is perhaps worthy to note that in other fisheries where firearms are not the selected method used to despatch fish on hooks and where wire traces are permitted and widely used, there are some advantages, and not just disadvantages, to sharks from ‘J’ hook use Shorter sets Use artificial baits (limited data) Firearms to dispatch fish Avoid known high shark densities Set and haul hooks in daytime X X X X X X 47
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Shark Depredation and Unwanted Byca
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Shark Depredation and Unwanted Byca
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 16 and 17: Shark Depredation and Unwanted Byca
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 99 and 100: Appendix 5 Japan Pelagic Longline F
Page 101 and 102: Japan Pelagic Longline Fisheries Fi
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Page 105 and 106: Japan Pelagic Longline Fisheries Ta
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Japan Pelagic Longline Fisheries In
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Japan Pelagic Longline Fisheries A5
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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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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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