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A critique of the ecosystem impacts of drifting and anchored FADs use by purse-seine tuna fisheries in the Westernand Central Pacific Ocean







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    Global spatio-temporal patterns in tropical tuna purse seine fisheries on drifting fish aggregating devices (DFADs): Taking a historical perspective to inform current challenges 2013
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    This study provides a historical overview of the use of drifting fish aggregating devices (DFADs) in purse seine fisheries since the early 1990s, using global tu fisheries datasets from the four tu Regiol Fisheries Magement Organizations (RFMOs). Tropical tu purse seine fisheries typically target large yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) tus on free-swimming schools and skipjack (Katsuwonus pelamis) and juveniles of yellowfin and bigeye associated with drifting objects. DFA Ds have ebled global skipjack catches to markedly increase, and have also introduced major scientific issues for all tu-RFMOs. In particular, they have strongly modified the fishing strategies of purse seiners that fish on a combition of free-swimming and DFAD-associated schools. Consequently, the cumulated search time traditiolly used to quantify nomil fishing effort to assess the status of tu stocks is inconsistent and cannot be used to derive time series of abundance indices from catch-per-un it of-effort (CPUE). In addition, the lack of information available on the construction, deployment, and use of DFADs has prevented effective monitoring of the fishing pressure over the last two decades exerted by purse seine fleets using this fishing mode. Juveniles of tropical tus represent a substantial proportion of purse seine catch on DFADs in the three oceans, which has raised particular concern for some bigeye stocks that have been subject to overfishing in the past. Catches of juvenile tus by DFAD fishing may also result in a decrease in recruitment for fisheries that target adult tus such as longliners. In addition, some demographic parameters of tus and other species associated with DFADs may be affected by the resultant habitat modification arising from the widespread deployment of DFADs. Evidence in the literature and provided by the ratio-estimator method suggest that fishing DFAD-associated schools may result in about 100 000 t of bycatch and discards annually. In additi on, there is further potential for ghost fishing related mortality of sensitive species such as marine turtles and pelagic sharks. In this context and following a precautiory approach, we filly discuss the increasing need for all tu-RFMOs to reduce, or at least monitor and control, the use of DFADs to mitigate their adverse effects not only on yellowfin and bigeye stocks but also on open-ocean ecosystems.
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    Statistics of the purse seine fleets of France’s overseas territories targeting tropical tunas in the Indian Ocean 2013
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    Statistical data for the France’s Overseas Territories (FRAT) purse seine fleet have been collected by the “Institut de Recherche pour le D ?eveloppement” (IRD) since 2001. Purse seiners registered in the harbour of Dzaoudzi, Mayotte, belong to the EU purse seine fleet of the Indian Ocean and data collection and processing are similar to the ones used for the French component of the fleet. Tropical tu purse seiners target yellowfin (Thunnus albacares), skipjack (Katsuwonus pelamis), and bigeye t u (Thunnus obe- sus) through two major fishing modes that result in different species and size composition of the catch: fish-aggregating device-associated (FAD) and free-swimming schools (FSC). Here, the acronym ”FAD” encompasses any type of drifting floating object to which tu schools can associate. This definition includes ”tural” objects (e.g. logs, palm branches) and anthropogenic floating objects, such as man- made bamboo rafts equipped with radio-range beacons, satellite transmitters and scanning sors. The fleet activities are described through a suite of fisheries indicators that provide information on fishing capacity and effort, catch, and catch rates for the 3 principal market tropical tus, with a particular focus on the year 2012.
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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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