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      Greenland shark ( Somniosus microcephalus) feeding behavior on static fishing gear, effect of SMART (Selective Magnetic and Repellent-Treated) hook deterrent technology, and factors influencing entanglement in bottom longlines

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          Abstract

          The Greenland Shark ( Somniosus microcephalus) is the most common bycatch in the Greenland halibut ( Reinhardtius hippoglossoides) bottom longline fishery in Cumberland Sound, Canada. Historically, this inshore fishery has been prosecuted through the ice during winter but winter storms and unpredictable landfast ice conditions since the mid-1990s have led to interest in developing a summer fishery during the ice-free season. However, bycatch of Greenland shark was found to increase substantially with 570 sharks captured during an experimental Greenland halibut summer fishery (i.e., mean of 6.3 sharks per 1,000 hooks set) and mortality was reported to be about 50% due in part to fishers killing sharks that were severely entangled in longline gear. This study investigated whether the SMART (Selective Magnetic and Repellent-Treated) hook technology is a practical deterrent to Greenland shark predation and subsequent bycatch on bottom longlines. Greenland shark feeding behavior, feeding kinematics, and variables affecting entanglement/disentanglement and release are also described. The SMART hook failed to deter Greenland shark predation, i.e., all sharks were captured on SMART hooks, some with more than one SMART hook in their jaw. Moreover, recently captured Greenland sharks did not exhibit a behavioral response to SMART hooks. In situ observations of Greenland shark feeding show that this species uses a powerful inertial suction mode of feeding and was able to draw bait into the mouth from a distance of 25–35 cm. This method of feeding is suggested to negate the potential deterrent effects of electropositive metal and magnetic alloy substitutions to the SMART hook technology. The number of hooks entangled by a Greenland shark and time to disentangle and live-release a shark was found to increase with body length.

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                Author and article information

                Contributors
                Journal
                PeerJ
                PeerJ
                PeerJ
                PeerJ
                PeerJ
                PeerJ Inc. (San Francisco, USA )
                2167-8359
                17 May 2018
                2018
                : 6
                : e4751
                Affiliations
                [1 ]Centre for Sustainable Aquatic Resources, Memorial University of Newfoundland , St. John’s, NL, Canada
                [2 ]Central and Arctic Region, Arctic Aquatic Research Division, Fisheries and Oceans Canada , Winnipeg, MB, Canada
                Author information
                http://orcid.org/0000-0001-7119-8876
                Article
                4751
                10.7717/peerj.4751
                5960585
                5e19c0be-77b8-4c1e-9ca8-9c2fd43bff26
                © 2018 Grant et al.

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ) and either DOI or URL of the article must be cited.

                History
                : 1 December 2017
                : 22 April 2018
                Funding
                Funded by: National Research Council of Canada
                Funded by: Fisheries and Oceans Canada
                Funded by: Department of Environment Government of Nunavut
                Funded by: Canadian Northern Economic Development Agency
                Funded by: Nunavut Offshore Allocation Holders Association
                This work was supported by the National Research Council of Canada, Fisheries and Oceans Canada, Department of Environment Government of Nunavut, Canadian Northern Economic Development Agency, and Nunavut Offshore Allocation Holders Association. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
                Categories
                Animal Behavior
                Conservation Biology
                Marine Biology

                greenland shark,longlines,shark deterrent technology,bycatch mitigation,inertial suction,feeding behavior,feeding kinematics

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