SCIENTIFIC COMMITTEE TENTH REGULAR SESSION Majuro, Republic of the Marshall Islands 6-14 August 2014 Bycatch in Longline Fisheries for Tuna and Tuna-like Species: a Global Review of Status and Mitigation Measures WCPFC-SC10-2014/ EB-IP-04

The history of global longline fishing illustrates the role of new technologies (e.g. vessel innovations, freezers, fishing gear), the expansion of fishing grounds, and the operational characteristics of the fleets (e.g. fleet sizes, fishing methods, product focus) in shaping today’s fishery. More recently, management regulations, the price of oil, the cost of labour, and market demand have also exerted an influence. At present, no more than 23% of the tuna in each ocean (Atlantic, Pacific, and Indian) is LL-caught. Although overall pelagic longline catches have decreased since 2004, global pelagic longline fishing effort has expanded since 2008 and currently there may be as many as 7,500 tuna longliners globally with nearly 60% of these <24m in length. Elasmobranchs (sharks, skates and rays) occupy a unique position somewhere along the spectrum between explicit target species and undesirable bycatch. Although underreporting is rampant, available data suggest that catches have fallen 14% since their peak in 2003. In longline fisheries bait type, soak time, hook shape, leader length and material, depth at which the hook is fished, and whether special gear is deployed to target sharks, all may determine shark catch rates. Vulnerability to hooking, and resilience to haulback and handling, will vary by species, size, area and fleet operational practices. Tuna Regional Fisheries Management Organizations (t-RFMOs) have recently begun assessing shark populations’ status but data limitations often hinder the drawing of firm conclusions. Finning bans and no-retention measures have been adopted but there is little information on their implementation or effectiveness. Mitigation measures such as circle hooks, nylon leaders and repellents/deterrents have been tested but results vary across fisheries, species and sizes. All but one of the seven species of sea turtles is threatened with extinction, and while globally longline fisheries may have less impact than net-based fisheries, significant population-level impacts may be occurring in some regions. The greatest concern is associated with loggerhead-longline interactions in the Atlantic; although impacts have been mitigated in some fisheries (e.g. the United States), the population continues to decline. Circle hooks and using finfish (rather than squid) bait have been shown to be effective either by reducing hooking or reducing hook swallowing. Other methods, such as avoiding preferred sea turtle habitat and use of deterrents will require further development before they can reliably mitigate impacts. Only one t-RFMO requires circle hook or finfish bait use to reduce sea turtle interactions, and there are few data to evaluate the extent to which population impacts continue. It is estimated that 50 000 – 100 000 seabirds are killed annually by interactions with pelagic longline fisheries. Many of these species, particularly albatrosses, are threatened with extinction. Recent advances in tracking technologies have facilitated mapping of where seabird-longline interactions are most likely. The Western and Central Pacific has been found to contain over 45% of the global total albatross and giant petrel breeding distributions with particular areas of high risk in the band between 20-40o in the North Pacific and between 20-50o in the South Pacific, especially around New Zealand. The most promising mitigation methods appear to be night setting, side-setting, line weighting and streamer lines, but further research on remaining limitations and the effectiveness of these methods in individual fisheries is needed. All of the five t-RFMOs require use of one or more of these methods in areas which overlap albatross distributions. However, compliance data are limited and improved observer coverage is essential for verification and to assess residual impacts. A wide range of marine mammals interact with longline fisheries in ways that are detrimental to the fishery but may be either positive (i.e. depredation from the hook provides a feeding opportunity) or negative (i.e. risk of hooking or entanglement) for the marine mammal. Although it is not often clear from fishermens’ reports of depredation which species are involved, it is most often the odontocetes (toothed whales and dolphins) which are implicated. In particular, pilot whale interactions in the western Atlantic and false killer whale interactions off Hawaii have triggered national mitigation plans for longline fisheries. As yet, none of the t-RFMOs have adopted management measures for marine mammal interactions. Research and testing of mitigation measures such as physical barriers (streamers, sleeves or cage devices), as well as acoustic techniques (deterrence or harassment), continues in order to ameliorate both marine mammal impacts and economic losses due to depredation in longline fisheries. At least 650 species of other bony fishes may be caught in association with pelagic longline fisheries but a lack of reporting requirements, low commercial value and frequent discarding, a supposed low vulnerability to fishing pressure, and/or the difficulties of species identification result in limited data. The most commonly encountered species appear to be dolphinfish, opah, oilfish, escolar and ocean sunfish. Some of these stocks are important as local food supplies and should be safeguarded for that reason. However, given the poor data quality, it remains unclear whether either these stocks or the ecosystem they help structure is at risk. It is therefore recommended that more attention be paid to 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, and the different mechanisms and behaviours that govern those interactions, provide an almost overwhelming array of topics to be addressed in any discussion of bycatch mitigation. Scientific 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, 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 must also be considered.