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Sharks: Bycatch in the tuna longline fishery in the Indian Ocean by Thai tuna longliners in 2012









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    Billfish fishery of Thailand 2013
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    Thai tu longline that composed of 3 tu longlines in 2007 and 2 tu longliners during 2008-2012. The main fishing ground was central and southern part of the Indian Ocean. This report was based on the data extracted from fishing longsheets which were delivered to Department of Fisheries, Thailand During 2007-2012, is summarized and calculated the hook rate in Catch Per Unit Effort (CPUE). The fishing operations were recorded 2,276 fishing days. The highest total catch was in 2010 with 607.69 tonne s followed by 2012, 2007, 2011, 2009 and 2008, respectively (494.95,461.64, 370.39, 295.23 and 265.57 tonnes). The highest CPUE was found in 2010 with 13.62 fish/1,000 hooks followed by 2012 and 2007, respectively (10.80 and 10.20 fish/1,000 hooks). The major catch species wer bigeye tu (Thunnus obesus) , yellowfin tu (T. albacores) Albacore tu (T. alalunga), swordfish and shark. In 2012, the numbers of individual billfish were 736 individual fishes with 25.05 tonnes. The highest total catch of Billfish was in 2010 with 80.58 tonnes followed by 2008, 2009, 2012, 2011 and 2007, respectively (59.35, 54.63, 25.05, 16.00 and 8.23 tonnes) The highest CPUE was found in 2008 and 2010 with 1.0 fish/1000 hooks.
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    National Report – Thailand 2013
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    Neritic tu species in the Andaman Sea Coast, Thailand comprise 7 species (Thunnus tonggol, Euthynnus affinis, Auxis thazard, A. rochie, Katsuwonus pelamis and Sarda orientalis, Scomberomorus spp.). These species were caught from purse seine, king mackerel gill net and trawl, while purse seine was the main fishing gear. The trend of neritic tu catches have been decreasing from 45,083 tons in 1997 to 13,093 tons in 1999. The production was quite stable around 10,711 and increase to 11,861 in 2009. These neritic tu species are more or less have its production trend similarity. Three Thai tu longliners were operated in the Indian Ocean in 2007 and in 2008- 2012 only two Thai tu longliners kept on fishing there. Fishing grounds were mainly in the western coast of Indian Ocean. The fishing operations were recorded 2,276 fishing days. The highest total catch was in 2010 with 607.69 tonnes followed by 2012, 2007, 2011, 2009 and 2008, respectively (494.95,461.64, 370.39, 295.23 and 265.57 tonne s). The highest CPUE was found in 2010 with 13.62 fish/1,000 hooks followed by 2012 and 2007, respectively (10.80 and 10.20 fish/1,000 hooks). The major catch species wer bigeye tu (Thunnus obesus) , yellowfin tu (T. albacores) Albacore tu (T. alalunga),swordfish and shark.
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    An overview of the bycatch landed by local and foreign tuna longliners in Mauritius for the period 2009 to 2012 2013
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    This paper presents by-catch estimates landed by tiol and foreign longliners fishing inside and outside the EEZ of Mauritius for the period 2009 to 2012. Some 100 licences are issued annually to foreign longliners to fish in the Exclusive economic zone (EEZ) of Mauritius. The average annual landing from these vessels during the period under report amounted to 3 102 tonnes of albacore tu which is the targeted species followed by 796 tonnes of yellowfin tu (Thunnus albacares), 360 tonnes of big-ey e tu (Thunnus obesus) and 1106 tons of by-catch comprising billfish, other tu-like species and sharks. A total of 21 196 tonnes of tu and tu-like species was transhipped in Port-Louis by non-licensed fishing vessels targeting albacore (Thunnus alalunga), from 2008 to 2012. The proportion of by-catch landed during this period varied between 28.9% and 39.4%. The total catch landed by non-licensed longliners targeting big-eye tu has increased over the years from 3495 tonnes in 2008 to 8125 tonnes i n 2012. The proportion of by-catch in the total catch seems to be the same (33.1%-47.0%) as compared to the level of by-catch of albacore-targeting fishing vessels (37.9%-39.4 %). The proportion of by-catch landed by longliners targeting swordfish (Xiphias gladius) varied between 37.2% to 49.6%. A comparison of shark landings by tu longliners and swordfish-targeting longliners was carried out: the levels of sharks in the total catch of longliners targeting big-eye tu are higher (7.9%-20.2%) than those targeting albacore (3.6%-8.03%). However, the catch of sharks was very significant in swordfish-targeting vessels varying between 24.3%-39.1% of the total catch in comparison to albacore-targeting fleets and big-eye targeting fleet. Sharks landed by swordfish-targeting vessels consisted mainly of blue shark (Prioce glauca) (74.2-84.2%) followed by moro (Isurus oxyrhinchus) (7.1-20.0%) and mako shark (Isurus paucus) (4.6-9.2%). Moreover, Mauritius has a small number of tiol boats targeting swordfish that operate in its EEZ. These boats also land a considerable amount of non-targeted tu and tu-like species including sharks. The by-catch levels for tiol boats targeting swordfish was higher (50.8%- 52.7% of the total catch) as compared to the FAD fishery whose by-catch varied between 27.9%- 42.9%.

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