See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/330818474 Technical mitigation to reduce marine mammal bycatch and entanglement in commercial fishing gear: lessons learnt and future directions Article in Reviews in Fish Biology and Fisheries · February 2019 DOI: 10.1007/s11160-019-09550-6 CITATIONS READS 0 144 2 authors: Sheryl Hamilton G. Barry Baker University of Tasmania University of Tasmania 24 PUBLICATIONS 366 CITATIONS 41 PUBLICATIONS 678 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: Population assessment of Auckland Islands and Chatham Island albatross species View project All content following this page was uploaded by G. Barry Baker on 06 February 2019. The user has requested enhancement of the downloaded file. Rev Fish Biol Fisheries https://doi.org/10.1007/s11160-019-09550-6 (0123456789().,-volV)( 0123456789().,-volV) REVIEWS Technical mitigation to reduce marine mammal bycatch and entanglement in commercial fishing gear: lessons learnt and future directions Sheryl Hamilton . G. Barry Baker Received: 17 September 2018 / Accepted: 12 January 2019 Ó Springer Nature Switzerland AG 2019 Abstract Fisheries bycatch is one of the biggest threats reliably effective technical solutions to reduce small to marine mammal populations. A literature review was cetacean bycatch in trawl nets are available, although undertaken to provide a comprehensive assessment and loud pingers have shown potential. There are currently no synopsis of gear modifications and technical devices to technical options that effectively reduce marine mammal reduce marine mammal bycatch in commercial trawl, interactions in longline fisheries, although development purse seine, longline, gillnet and pot/trap fisheries. of catch and hook protection devices is promising. Successfully implemented mitigation measures include Solutions are also needed for species, particularly acoustic deterrent devices (pingers) which reduced the pinnipeds and small cetaceans, that are not deterred by bycatch of some small cetacean species in gillnets, pingers and continue to be caught in static gillnets. Large appropriately designed exclusion devices which reduced whale entanglements in static gear, particularly buoy pinniped bycatch in some trawl fisheries, and various lines for pots/traps, needs urgent attention although there pot/trap guard designs that reduced marine mammal is encouraging research on rope-less pot/trap systems and entrapment. However, substantial development and identification of rope colours that are more detectable to research of mitigation options is required to address the whale species. Future mitigation development and bycatch of a range of species in many fisheries. No deployment requires rigorous scientific testing to deter- mine if significant bycatch reduction has been achieved, as well as consideration of potentially conflicting miti- Electronic supplementary material The online version of gation outcomes if multiple species are impacted by a this article (https://doi.org/10.1007/s11160-019-09550-6) con- fishery. tains supplementary material, which is available to authorized users. Keywords By-catch Á Cetacean Á Gillnet Á Longline Á S. Hamilton (&) Á G. B. Baker Pinniped Á Trawl Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS 7001, Australia e-mail: [email protected] S. Hamilton Introduction Centre for Marine Socioecology, University of Tasmania, Hobart, TAS 7001, Australia Marine mammals are incidentally killed in a range of fisheries throughout the world (Lewison et al. 2014; S. Hamilton Á G. B. Baker Latitude 42 Environmental Consultants Pty Ltd., 114 Read et al. 2006). This bycatch in active fishing gear is Watsons Rd, Kettering, TAS 7155, Australia 123 Rev Fish Biol Fisheries one of the biggest threats to marine mammal popula- expansion from previously published assessments. tions, particularly cetaceans (whales, dolphins and This paper presents the first comprehensive global porpoises) and pinnipeds (e.g. seals and sea lions) review of technical mitigation measures designed to (Jaiteh et al. 2013;Read2008; Reeves et al. 2013). As reduce marine mammal bycatch in commercial fishing these species are long-lived with high adult survival gear, including assessments of mitigation testing, and low breeding productivity, populations are often effectiveness and, where relevant, operational deploy- slow to recover from declines, even under conducive ment, and a synthesis of best practice mitigation and environmental conditions. Therefore, anthropogenic areas requiring greater attention. activities that increase mortality levels, such as fisheries bycatch, can have significant, long-term population impacts (Gilman 2011; Lewison et al. Methods and scope 2004; Reeves et al. 2003). Cetaceans and pinnipeds interact with fisheries as Although there has been considerable progress in they may: (1) feed on the same target species or some fisheries regarding the development, testing and associated non-target species of a fishery, (2) be implementation of mitigation measures to reduce attracted to fishing operation discards, and/or (3) marine mammal bycatch in commercial fishing gear, passively encounter fishing gear in the water column much of this information is not easily accessible. A (Fertl and Leatherwood 1997; Hamer et al. 2012). literature review was undertaken using a range of These interactions may result in the bycatch of sources including peer-reviewed journals, unpub- individuals caught in active fishing components (e.g. lished reports, magazine articles, conference papers, nets, hooks, traps), or entangled in supporting gear and websites, and information from government and non- lines. Bycatch in trawl, purse seine, longline, gillnet government organisations. An electronic literature and pot/trap fisheries has been identified as a major search was conducted up to and including August threat to many species (Hall 1998; Hamer et al. 2012; 2018 using Web of Science and Google Scholar. Hamer and Goldsworthy 2006; Hamer et al. 2008; Search terms were bycatch, by-catch and/or mitigat* Knowlton et al. 2012; Reeves et al. 2013; Werner et al. combined with: fisher*, trawl, purse seine, longline, 2015). Other gear types, such as those used in troll and gillnet, pot, trap, line, cetacean, whale, dolphin, squid jigging fisheries, are considered to be more porpoise, pinniped, seal, sea lion in any field. Refer- selective in targeting species and, therefore, have less ences from other published papers and the authors’ bycatch risk (Wakefield et al. 2017). personal bibliographic resources were used to identify Over the past decade, there has been heightened relevant papers. Key researchers were contacted via awareness and attention on the development of email or ResearchGate (https://www.researchgate.net/) solutions to reduce fisheries bycatch. For example, to access relevant non-published reports. the Food and Agriculture Organization of the United Studies on the development and implementation of Nations (FAO), as part of an ongoing commitment to technical mitigation measures (i.e. gear modifications bycatch management work, convened a workshop to and mitigation devices) for marine mammal bycatch in consider means to reduce marine mammal mortality in commercial trawl, purse seine, longline, gillnet and fisheries and aquaculture operations (FAO 2018). pot/trap fishing gear were reviewed. Fisheries not Also, a number of bycatch mitigation reviews have considered to be high risk to marine mammal species, focussed on particular aspects of mitigation or gear such as trolling and jigging (Arnould et al. 2003), and type, or on certain species or species groups (Dawson mitigation of mortalities from lost, discarded or et al. 2013; Geijer and Read 2013; Hamer et al. 2012; abandoned gear (i.e. ghost fishing) were not included. How et al. 2015; Laverick et al. 2017; Leaper and Reviewed studies predominantly addressed cetacean Calderan 2018; Werner et al. 2006, 2015). However, and/or pinniped bycatch as most mitigation research there is no readily accessible synthesis of best practice has focussed on these taxa. mitigation methods for marine mammals and, further- Technical measures are presented on a fishing gear more, the high level of bycatch that continues to occur basis (trawl, purse seine, longline, gillnet and pot/trap) in fisheries around the world (Gray and Kennelly with the exception of pingers and a range of weakened 2018; Reeves et al. 2013) necessitates an update and gear, which are applicable to different fishing gears 123 Rev Fish Biol Fisheries and are therefore more effectively dealt with in a Mitigation relevant to multiple types of fishing collated section. For each measure, the scientific gear evidence for mitigation effectiveness, caveats or uncertainties in the methods or results, research Pingers (Acoustic deterrent devices) requirements and, where possible, recommendations for effective operational implementation were Pingers, small electronic devices with relatively low identified. acoustic outputs (\ 160 dB), were developed to Although outside the scope of this review, it was reduce high levels of small cetacean bycatch in apparent that effective bycatch mitigation strategies gillnets (Dawson et al. 2013; Kraus et al. 1997; often comprise a suite of management measures in Reeves et al. 2013). Pingers also include louder conjunction with technical mitigation. These include devices ([ 132 dB) to deter marine