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The capture depth of the dominate bycatch species and the relationship between their catch rates and the sea surface temperature









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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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    Book (series)
    Bycatch in longline fisheries for tuna and tuna-like species: a global review of status and mitigation measures 2014
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    This publication is the third in a series on bycatch in global tuna fisheries. Dealing with longline fisheries, its scope is defined taxonomically to comprise only non-tuna and non-tuna-like species. The history of longline fishing illustrates the role of new technologies, the expansion of fishing grounds, and the operational characteristics of the fleets in shaping today’s fishery. More recently, management regulations, the price of oil, the cost of labour, and market demand have also exerted a n influence. No more than 23 percent of the tuna in each ocean is longline-caught. However, there may be up to 7 500 tuna longliners globally with almost 60 percent of them less than 24 m in length. Available data suggest that elasmobranch catches have fallen 14 percent since their peak in 2003. In longline fisheries, shark catch rates may be determined by bait type, soak time, hook shape, leader length and material, depth at which the hook is fished, and whether special gear is deployed to targ et sharks. Vulnerability to hooking, and resilience to haulback and handling, vary by species, size, area and fleet operational practices. Tuna regional fisheries management organizations (t-RFMOs) assess the status of shark populations but data limitations often hinder firm conclusions. There is little information on the implementation or effectiveness of finning bans and no-retention measures. Mitigation measures have been tested but results vary. Six of the seven species of sea turtles are th reatened with extinction, and while longline fisheries may have less impact than net-based fisheries, significant populationlevel impacts may be occurring in some regions. The greatest concern is associated with loggerhead–longline interactions in the Atlantic. Circle hooks and using finfish bait have proved effective mitigation techniques either by reducing hooking or hook swallowing. Other methods require further development. Interactions with pelagic longline fisheries kill 50 000–100 000 sea birds annually. Many of these species, particularly albatrosses, are threatened with extinction. Recent advances in tracking technologies have facilitated mapping of where interactions are most likely. The Western and Central Pacific contains more than 45 percent of the global total albatross and giant petrel breeding distributions. The most promising mitigation methods appear to be night setting, side-setting, line weighting and streamer lines, but further research is needed. All five t-RFMOs r equire use of one or more of these methods in areas that overlap albatross distributions. However, compliance data are limited and improved observer coverage is essential. Marine mammals’ interactions with longline fisheries are detrimental to the fishery but may be positive or negative for the mammals. Although it is often unclear which species are involved, pilot whale interactions in the western Atlantic and false killer whale interactions off Hawaii have triggered national mitigation plans. No t-RFMO has adopted management measures for marine mammal interactions. Research and testing of mitigation measures continue in order to ameliorate both marine mammal impacts and economic losses to industry from depredation. At least 650 species of other bony fishes may be caught in association with pelagic longline fisheries, e.g. dolphinfish, opah, oilfish, escolar and ocean sunfish. Some of these stocks are important as local food supplies. However, it is unclear whether these stocks or the ecosystem they help structure is at risk. More attention should focus on improving fishery statistics and initiating basic monitoring of these stocks’ status. The diversity of pelagic longline gear designs and fishing methods, the variety of habitats they are deployed in, the thousands of marine species they may interact with, v and the different mechanisms and behaviours that govern those interactions provide an array of topics to be addressed in any discussion of bycatch mitigation. Scientifi c and technical issues in mitigation including effects across taxa, effects of combinations of measures, economic and safety considerations, underlying biological mechanisms, handling and post-release mortality, and non-fishery impacts must all be addressed. In addition, it is also necessary to consider issues such as who takes the lead for ensuring mitigation is sufficient for the population as a whole, how to devise effective mitigation implementation strategies, and whether gear modification should be used in concert with more sweeping measures.
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    Provision of scientific advice for the purpose of the implementation of the EUPOA sharks. Final Report. European Commission, Studies for Carrying out the Common Fisheries Policy (MARE/2010/11 - LOT 2) 2013
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    The scope of the European Union Plan of Action for Sharks covers directed commercial, by-catch commercial, directed recreatiol, and by-catch recreatiol fishing of any chondrichthyans within European Union waters. It also includes any fisheries covered by current and potential agreements and partnerships between the European Union and third countries, as well as fisheries in the high seas and fisheries covered by RFMOs maging or issuing non-binding recommendations outside European Union waters. S cientific advice for the purpose of the magement of shark species in the high seas is carried out mainly via the Scientific Committees of the relevant Regiol Fisheries Magement Organisations (RFMO), as well as through specific projects by tiol institutes, and other research organisms. However, the level of knowledge concerning many shark populations in the high seas of the Atlantic, Indian and Pacific Oceans is far from satisfactory. It is therefore necessary to identify gaps in the current know ledge of fisheries, biology and ecology of sharks that should be filled in order to support advice on sustaible magement of elasmobranches' fisheries and undertaking studies to fill those gaps. Therefore, the objective of this project is to obtain scientific advice for the purpose of implementing the EUPOA on sharks as regards the facilitation of monitoring fisheries and shark stock assessment on a species-specific level in the high seas. The study is focused on major elasmobranch species caught by both artisal and industrial large pelagic fisheries on the High Seas of the Atlantic, Indian and Pacific area, which are currently monitored and potentially maged by respective Tu RFMOs. Specifically, firstly the study aims to collate and estimate historical fisheries data especially on species composition of catches, catches and effort, size frequencies in order to identify the gaps in the current availability of fishery statistics as well current knowledge biology and ecology of sharks tha t should be filled in order to support the scientific advice provided to RFMOs on sustaible magement of elasmobranch fisheries. And secondly, the project aims to review and prioritise the gaps identified to develop a research program to fill those gaps in support for the formulation of scientific advice for magement of sharks. The data and knowledge gaps identified through Phase I will allow focusing and prioritising the future research. From this summarisation of Phase I it will be clear as to what data is available for providing magement advice for shark species, and where gaps in the data render this task difficult. In a second step, recommendations for data collection improvements as well as research necessities and activities will be described. The data collected in Phase I of the project gives a complete picture of the current data availability of information about catch and effort, observer programs, size frequency information, biological information and fishery indicators that may support the assessment of major shark species in Tu RFMOs. In spite of the importance of shark catches by industrial fleets, they have traditiolly consisted of bycatch of commercial fisheries and sharks are most often discarded or finned. Therefore, most of the times, shark catches are not recorded, especially with the required level of resolution, and catches must be estimated by statistical procedures based on observer data, fishing effort and different covariates. Moreover, the informatio n recorded is not usually RFMO) databases. The information on shark bycatch is scarce and their estimates found in the literature are not homogenous which made the raising and/or estimates of ratios (by-catch/target catch) uncertain due to various assumptions made (e.g. conversion of the estimates in number of individuals into weight without any information on the mean size per species). In summary, the main difficulties and data gaps identified in the project can be described as follows: there is a lack of shark reporting in artisal and coastal fisheries; there is a lack of shark reporting in industrial fisheries and when is reported usually is not broken down by species; there is a lack of any size frequency data; there is a lack of regiol biological/ecological information for sharks; there are difficulties to access to the data both at RFMO level and at a country level; species misidentification which affect the collection of fishery statistics; low observer coverage for most of the fleets/areas; difficulties with the use of logbook data for shark assessment (misidentification, underreporting, change in targeting practice). The work carried out in first phase of the project focuses on the collection of fishery information publicly available, mainly in the website public domain of the RFMOs in the Indian, Pacific and Atlantic Ocean as well as in the Mediterranean Sea (ICCAT- GFCM, IOTC, IATTC, and WCPFC) but also on information available in the literature, most of which com es from documents presented at the scientific meetings or workshops of RFMOs. The RFMO data administrators were also contacted in order to obtain any additiol fishery statistics data. Similarly, information from flag states, and from EU- member states, was requested in order to improve the information available on discards levels, size frequencies and biological information. Apart from RFMO official statistics, and in order to get more accurate and altertive catch data, shark catch estimations f or the most recent period were appraised based on fleet specific ratios of shark catch over tu (or target) catches. This was done in a two step process, first a general ratio between shark catches over tu (target) catch was applied to estimate total shark catches for major fisheries and, then, the relative proportion by species in the catch was applied to estimate shark catches by species. Those ratios were obtained from the literature search and/or data from observer programs available in the R FMO or in the literature. This exercise allows identifying the fleets that could be mainly responsible for the catch of the main shark species included in the study based on the best assumption of the shark catch over target species catch ratios derived from the literature but also allows identifying the main impacted shark specis by fisheries in each areas as well as the main origin of underreporting. In the Atlantic and Pacific (east and west), the Longline fleet targeting sharks, swordfish an d/or tropical tus is the most important métier catching sharks; which contributes with 59 %, 86 % and 95 % to the total shark catches respectively. On the contrary, the picture in the Indian Ocean is different where gillnet (GN - sensu lato) are contributing with 61 % of the total shark catch in comparison to 18 % for longliners. In general, the species composition of the sharks in different métiers is similar in all Oceans as well as in the Mediterran Sea. For example, Longline (LL - sensu lato ) impacts mainly blueshark and shortfin mako and in a minor extend hammerhead, thresher, silky and oceanic whitetip sharks; whereas Gillnet (GN - sensu lato) are impacting mainly silky, thresher, Oceanic whitetip, and shortfin mako sharks. The catch of silky and oceanic whitetip shark for the longline fleet in the West Pacific is higher than other longline fleets of other Oceans because they are operating in more equatorial waters. Although, in all the Oceans, the contribution to the total catch of Purse seines is minor (maximum of 5 % of total catch in the West Pacific); the species composition of purse seines catch is clearly domited by silky and oceanic whitetip sharks. In all Oceans the main species impacted is blueshark with around 65-75 %, with the exception of the Indian Ocean and Mediterranean Sea, of the total shark catch. The contribution of the rest of the species can vary depending on the relative contribution of different fleets as well as the spatial distribution of the d ifferent fleets. However, in general the blueshark catch is then followed by shortfin mako, hammerhead, silky, thresher, Oceanic withetip shark. In the Indian Ocean, the blueshark contribution to total shark catch is around 35 % followed by silky shark (21 %), thresher (16 %), Oceanic whitetip (11 %), shortfin mako (10 %) and hammerheads (6 %). And in the Mediterrenean, blueshark contribution is around 50 % while other species make up the rest: thresher sharks (25 %), mako sharks (13.3 %), tope shark (6.1 %), rays (3.5 %), and porbeagle (1 %). The comparison between the declared value and the estimated value can be considered as a figure for undereporting. For example, it is worth mentioning that the total average amount of the investigated species estimated is 1.5, 13 and 7 times higher than the average amount declared in the Atlantic Ocean, Mediterranean Sea and Indian Ocean, respectively. However, as the estimation carried out in this alysis was based on ratio of shark catch over to tal target catch there is high uncertainty on fil estimations coming from different sources; such as métier classification, from target species quantities declared and from the shark/target catch ratio used to estimate the shark species investigated; which recommend to take these estimations with caution. It was not possible to apply this methodology to the Eastern and Western Pacific due to the lack of access to disaggretate tu/target species catches from the IATTC/WCPFC public databases. And t he data above should be considered in the light of the different species productivity and susceptibility of a given species to a giving métier. This is important to take into account because in some cases a minor catch of one species from all fleets, or one fleet in particular, can have a great impact if the species in question is more vulnerable showing low productivity and high susceptibility to the fleet(s). So, it is important to consider the results above in the framework of Ecological Risk Assessment (ERA) which can help to identify priorities for observer programs/research efforts. Filly, data gaps identified in relation to shark fishery statistics have been summarized with the aim to develop a research framework that would allow filling those gaps in order to assess and mage the shark population worldwide in a sustaible manner. The design of such programme is benefited and integrates all the information collected through phase I. For example, the data and knowledge gaps identif ied and listed/inventoried through Phase I allows focusing and prioritised the future research. From this summarisation of Phase I it is clear as to what data is available for providing magement advice for shark species, and where gaps in the data render this task difficult. At this stage, recommendations for data collection improvements as well as research necessities and activities are described. As such, the review of existing information; as well as the identification of information gaps, ma in shark species impacted and main métier responsible for major shark catch; presented above provides the basis for development of a research program and priorities for the assessment of the status of sharks in Tu RFMOs. As it is not possible to develop a research program for all the Tu RFMOs, a general framework to develop the research program in support of the scientific advice for shark magement is proposed; which includes: (1) a research framework to identify the main species and fleets that needs to be prioritized for the collection of fishery data and information in order to assure the assessment of principal shark species regiolly in the Tu RFMOs; (2) a general recommendations for all Tu RFMOs to improve the data collection to fill the gaps identified above; and (3) options for magement and mitigation measures for sharks. The research framework is proposed to be organized in three steps: (i) estimation of shark catches by species using the method proposed here which allows ident ifying the most impacted shark species and the métier most affecting those species; (ii) a prelimiry Ecological Risk Assessment (or other prelimiry assessment based on fishery indicators) by fleets which allows to identify the most vulnerable species to focus the efforts in conjunction with point (i); and (iii) specific recommendations of how to apply possible magement measures, to improve data collection and assessment of those fleets/species identified as priorities based on points (ii) and (i ii). The implementation of the three steps is highly related. The project also recommends actions to fill the identified gaps structured in sections as data collection, data reporting, data resolution, data access, and assessment. As the data collected through phase I give a complete picture of what are the main fleets targeting the more important shark species caught in the Tu RFMOs, both EU and other countries catching shark, as well as the extent of their volume; this exercise also helps to i dentify the different species for which more focus is needed and those that are supposed to be caught in a lesser extent. For example, this helps to focus the target or more important fleets to monitor and design specific representative observer schemes for those fleets as necessary. Having in mine the data gaps for major fisheries impacting pelagic sharks stocks in the different t-RFMOs Conventions areas as well as the most important metier catching sharks and most impacted shark species; the p roject proposes some possible solutions and recommendations for the implementation of observers programmes on those fisheries, aiming to improve shark data collection, mely regarding shark catch and discards: species composition; vessel mortality; size and sex data. Magement measures are essential when a given stock is seriously affected by the fishing activity and are aimed at limiting the impact of this activity. The election of a measure will depend on the stock status, on the behavior of the species, on the species being target or not, etc.; but the project summarizes several options of magement and mitigation measures applicable to shark species.

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