Disentanglement of Cape fur seals (Arctocephalus pusillus pusillus) with reversible medetomidine-midazolam-butorphanol.

Brett R Gardner,Steven A Mccue,Pieter G.H Kotze,Maryke Musson,S Mduduzi Seakamela,Brandon Spolander

doi:10.4102/jsava.v92i0.2119

Brett R Gardner, Steven A Mccue + Show 4 more

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https://doi.org/10.4102/jsava.v92i0.2119

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Abstract

Anaesthesia in pinnipeds is considered a much higher risk than in most terrestrial mammals because of their frequent proximity to water and physiological and anatomical adaptations related to diving, which also influence their anaesthesia management. Anaesthetising and immobilising entangled seals does not allow for selection of animals that are at a safe distance from the water’s edge. Medetomidine-midazolam-butorphanol (MMB) sedation was trialled on eight entangled Cape fur seals (CFS) (Arctocephalus pusillus pusillus) to determine if it was safe to use on animals that entered the water post-darting. The MMB was given at an estimated dose of 0.03 mg/kg, 0.2 mg/kg and 0.2 mg/kg, respectively, via remote darting. Sedation was reversed with intramuscular atipamezole (0.15 mg/kg) and naltrexone (0.4 mg/kg) to antagonise the effects of medetomidine and butorphanol, respectively. Moderate sedation was achieved in six animals. Six of the animals entered the water after being darted. There was a single mortality and a single animal that was too lightly sedated for capture. The preliminary results indicate that MMB produces suitable sedation for disentanglement of CFS. Additionally, MMB might be suitable for application to field-based biological research.

Highlights

Sedation and anaesthesia of otariid seals has advanced significantly in the last decade, producing safer outcomes for these marine mammals (Haulena & Schmitt 2018)
Unpublished disentanglement data (1990–2008) from the Victoria & Alfred (V&A) Waterfront (Cape Town) revealed that the majority of seal entanglements were from fishery products such as raffia cord, polypropylene box bands and monofilament fishing line (Department of Environment, Forestry and Fisheries [DEFF], unpublished data)
Comparing the published literature for the MMB combination in otariid seals, it appears that the midazolam and butorphanol dose is fairly consistent throughout its use in captive California sea lions (CSLs) (Spelman 2004), wild CSLs caught in haul-out traps and manually injected (Melin et al 2013) and wild CSLs darted with MMB (Frankfurter et al 2016)

Summary

Introduction

Sedation and anaesthesia of otariid seals has advanced significantly in the last decade, producing safer outcomes for these marine mammals (Haulena & Schmitt 2018). Pharmacological immobilisation of otariid seals has been associated with a high rate of mortality (Geschke & Chilvers 2009) Much of this was attributed to the presence of water near sedated animals and their specific physiological adaptations to diving (Baylis et al 2015; Haulena & Schmitt 2018). Cape fur seals (CFS) (Arctocephalus pusillus pusillus) interact with human activities at harbours along their range, most notably on the west coast (south-east Atlantic Ocean). These interactions are most evident at fishing harbours such as Cape Town and Hout Bay. Fishing harbours present haul-out and scavenging opportunities for CFSs, including interactions with anthropogenic debris. Unpublished disentanglement data (1990–2008) from the Victoria & Alfred (V&A) Waterfront (Cape Town) revealed that the majority of seal entanglements were from fishery products such as raffia cord, polypropylene box bands and monofilament fishing line (Department of Environment, Forestry and Fisheries [DEFF], unpublished data)

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