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Length frequency distributions of billfishes (Xiphiidae and Istiophoridae) from Indonesian tuna longline observer data









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    Report of the Eleventh Session of the IOTC Working Party on Billfish 2013
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    The Eleventh Session of the Indian Ocean Tu Commission?s (IOTC) Working Party on Billfish (WPB) was held in La Réunion, France, from 18 to 22 September 2013. A total of 24 (23 in 2012) participants attended the Session, including one invited expert, Dr. Humber Andrade, from the Universidade Federal Rural de Permbuco, Brazil. The meeting was opened on 18 September, 2013 by the Chair, Dr Jérôme Bourjea (La Réunion, France), who welcomed participants to La Réunion, France. Catch, Catch-and-effort, Size data The WPB RECOMMENDED that all CPCs assess and improve the status of catch-and-effort data for marlins (by species) and sailfish, noting that improvements to the data for the EU fleets and its provision to the IOTC Secretariat, would be most beneficial to the work of the WPB. (para. 25) Effect of piracy on billfish fisheries The WPB NOTED that, although no specific alysis of the impacts of piracy on fisheries in the Indian Ocean were presented at this meeting, paper IOTC–2013–WPB11–07 Re v_1 indicated that there has been a substantial displacement of catch (Fig. 1) and effort eastward (Fig. 2). Since 2004, annual catches have declined steadily, largely due to the continued decline in the number of active Taiwan,Chi longliners in the Indian Ocean (Fig. 3). In recent years, the proportion of fishing effort of the Japanese longline fleet sharply decreased in the north-western Indian Ocean (off the Somalia coastline), while fishing effort increased in the area south of 25°S, especia lly off western Australia. (para. 40) The WPB NOTED that the relative number of active longline vessels in the IOTC area of competence have declined substantially since 2008 (Fig. 3), and AGREED that this was likely due to the impact of piracy activities in the western Indian Ocean. Since 2011, there has been an increase in the relative number of active longline vessels in the Indian Ocean for Japan (68 in 2011 to 98 in 2012), Chi (10 in 2011 to 32 in 2012) and the Philippines (2 in 2011 to 14 i n 2012) (Fig. 3). (Para. 41) Pakistan gillnet fishery RECALLING IOTC Resolution 12/12 to prohibit the use of large-scale driftnets on the high seas in the IOTC area, paragraph 1, which states: “1. The use of large-scale driftnets on the high seas within the IOTC area of competence shall be prohibited.” “Large-scale driftnets” are defined as gillnets or other nets or a combition of nets that are more than 2.5 kilometers in length whose purpose is to enmesh, entrap, or entangle fish by drifting on the surface of, or in, the water column.”, the WPB RECOMMENDED that the SC note the findings of the study that gillnets in excess of the 2.5 km limit are being used by the gillnet fleets of Pakistan on the high seas, in contravention of Resolution 12/12. (para. 44) Revision of the WPB workplan The WPB RECOMMENDED that the SC consider and endorse the workplan and assessment schedule for the WPB for 2014, and tentatively for future years, as provided at Appendix XII and Appendix XIII, respectivel y. (para 192) Consolidated recommendations of the Eleventh Session of the Working Party on Billfish The WPB RECOMMENDED that the Scientific Committee consider the consolidated set of recommendations arising from WPB11, provided at Appendix XIV, as well as the magement advice provided in the draft resource stock status summary for each of the billfish species under the IOTC mandate: (para 205) o Black marlin (Makaira indica) – Appendix VII o Blue marlin (Makaira nigricans) – Appendix VIII o Strip ed marlin (Tetrapturus audax) – Appendix IX o Indo-Pacific sailfish (Istiophorus platypterus) – Appendix X o Swordfish (Xiphias gladius) – Appendix XI ???????????????????A summary of the stock status for billfish species under the IOTC mandate is provided in Table 1.
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    Size frequency – equations used to estimate standard lengths and estimate 2013
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    The available data on the sizes of billfish species caught by the different fisheries are presented as:??Size frequency data available: The size frequency data available in the IOTC databases is presented in (xls files compressed with WinZip): • FL_SWO.zip (as of 15-07-2013), contains the available data for swordfish • EFL_BLM.zip (as of15-07-2013), contains the available data for black marlin • EFL_BUM.zip (as of 15-07-2013), contains the available data for blue marlin • EFL_MLS_rev.zip (as of 13-09-2013), contains the available data for striped marlin • EFL_SFA.zip (as of 15-07-2013), contains the available data for Indo-Pacific sailfish Or click here if you want to download the above five files in one go FL_ALL_rev.zip The following standard lengths are used for billfish species: • Fork length: straight length from the tip of the lower jaw to the fork of the tail. Used for swordfish (SWO) • Eye to fork length: straight length from the eye orbit to the fork of the tail. Used for marl ins (BUM, BLM, MLS) and Indo-Pacific sailfish (SFA). All size data strata not recorded as standard length was converted into standard length by using the equations available for each species. Fish recorded under size class intervals other than those used for billfish species was assigned to the corresponding  size class interval(s) for each species (first class is 15cm for all billfish species and class interval is 3cm). Equations: The equations used to estimate standard lengths from non-standar d measurements and to estimate weight from the available lengths can be found in Equations (as of 25-06-2013) Details about the type of SF data available can be found in SF_Reference.zip.
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    National Report – Australia 2013
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    Pelagic longline and purse seine are the two main fishing methods used by Australian vessels to target tu and billfish in the Indian Ocean Tu Commission (IOTC) Area of Competence. In 2012, three Australian longliners from the Western Tu and Billfish Fishery and one longliner from the Eastern Tu and Billfish Fishery operated in the IOTC Area of Competence. They caught 13.1 t of albacore (Thunnus alalunga), 167.4 t of bigeye tu (Thunnus obesus), 23.0 t of yellowfin tu (Thunnus albacares), 209.3 t of swordfish (Xiphius gladius) and 2.5 t of striped marlin (Tetrapturus audax). These catches represent approximately 13 per cent of the peak catches taken by Australian vessels fishing in the IOTC Area of Competence in 2001, for these five species combined. In addition, Australian vessels using minor line methods took a small amount of catch. The number of active longliners and levels of fishing effort have declined substantially in recent years due to reduced profitability, primarily as a resu lt of lower fish prices and higher operating costs. The catch of southern bluefin tu (Thunnus maccoyii) in the purse seine fishery was 4503 t in 2012. A small amount of skipjack tu (Katsuwonus pelamis) was caught by purse seine fishing in 2012 (0.2 t). In 2012, less than 1 t of shark was landed by the Australian longline fleet operating in the IOTC Area of Competence and 11 371 sharks were discarded/released. In 2012, 17.8 per cent of all hooks set in WTBF longline operations were observed over three trips in the IOTC Area of Competence.

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