Abstract
Entanglement in fishing gear, when not acutely fatal, is a persistent life-threatening problem for gray seals (Halichoerus grypus) on the northeast coast of the United States.1,2 Primarily manifesting as constricting circumferential neck wraps of monofilament netting, these entanglements can cause severe lacerations, impede feeding and diving, increase susceptibility to infection, and slowly lead to mortality.3,4 Mitigating these human interactions is complicated by gray seal haul-out behavior, which involves high density herds occurring at or near the water's edge on tidally-dependent sand bars.3 Recently, The Marine Mammal Center (TMMC) developed a remote sedation system using a dart equipped with an acoustic transmitter to aid with tracking and capture of entangled sea lions in California.5 In 2015 and 2016, the International Fund for Animal Welfare worked with TMMC to determine the feasibility of using their system to dart, track and capture entangled gray seals on Cape Cod, MA. During three weeks of fieldwork, four gray seals were successfully darted from a vessel with combination of midazolam (0.32 mg/kg) and medetomidine (0.021 mg/kg), tracked with a unidirectional hydrophone, captured with hoop and/or seine nets, disentangled, treated, satellite tagged, and immediately released. On physical examination, entanglement wounds were more severe than appreciated from remote visual or photographic evaluation. After release, all four satellite tags demonstrated typical gray seal movement patterns for at least three months. To the authors' knowledge, these are the first successful remote sedation cases in free-ranging entangled phocid seals to date.
Acknowledgements
The authors would like to thank Mendy Garron at National Oceanographic and Atmospheric Administration (NOAA) Greater Atlantic Region, Deb Fauquier, Sarah Wilkin, and Teri Rowles at NOAA Marine Mammal Health and Stranding Response Program for supporting this effort. Thanks are also owed to Dr. Martin Haulena for valuable input on phocid sedation drug choices and dosing. We also thank the Greater Atlantic Regional Stranding Network members, the Northeast Fisheries Science Center, and Geno DeRango of TMMC for field support. Additionally, IFAW's disentanglement program would not be possible without the efforts of its stranding volunteers and interns. All activities were conducted under NMFS permit #18786.
* Presenting author
Literature Cited
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