Dead tired: evaluating the physiological status and survival of neonatal reef sharks under stress

Bouyoucos, Ian A., Weideli, Ornella C., Planes, Serge, Simpfendorfer, Colin A., and Rummer, Jodie L. (2018) Dead tired: evaluating the physiological status and survival of neonatal reef sharks under stress. Conservation Physiology, 6 (1). coy053.

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Abstract

Marine protected areas (MPAs) can protect shark populations from targeted fisheries, but resident shark populations may remain exposed to stressors like capture as bycatch and environmental change. Populations of young sharks that rely on shallow coastal habitats, e.g. as nursery areas, may be at risk of experiencing these stressors. The purpose of this study was to characterize various components of the physiological stress response of neonatal reef sharks following exposure to an exhaustive challenge under relevant environmental conditions. To accomplish this, we monitored markers of the secondary stress response and measured oxygen uptake rates (⁠ṀO2⁠) to compare to laboratory-derived baseline values in neonatal blacktip reef (Carcharhinus melanopterus) and sicklefin lemon sharks (Negaprion acutidens). Measurements occurred over three hours following exposure to an exhaustive challenge (gill-net capture with air exposure). Blood lactate concentrations and pH deviated from baseline values at the 3-h sample, indicating that both species were still stressed 3 h after capture. Evidence of a temperature effect on physiological status of either species was equivocal over 28–31°C. However, aspects of the physiological response were species-specific; N. acutidens exhibited a larger difference in blood pH relative to baseline values than C. melanopterus, possibly owing to higher minimum ṀO2⁠. Neither species experienced immediate mortality during the exhaustive challenge; although, single instances of delayed mortality were documented for each species. Energetic costs and recovery times could be extrapolated for C. melanopterus via respirometry; sharks were estimated to expend 9.9 kJ kg−1 (15% of energy expended on daily swimming) for a single challenge and could require 8.4 h to recover. These data suggest that neonatal C. melanopterus and N. acutidens are resilient to brief gill-net capture durations, but this was under a narrow temperature range. Defining species' vulnerability to stressors is important for understanding the efficacy of shark conservation tools, including MPAs.

Item ID: 56356
Item Type: Article (Research - C1)
ISSN: 2051-1434
Keywords: bycatch, marine protected areas, oxygen uptake rates, physiological stress response, shark nursery areas, temperature
Copyright Information: © The Author(s) 2018. Published by Oxford University Press and the Society for Experimental Biology. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
Funders: Australian Research Council (ARC), L'Oréal-United Nations Educational, Scientific and Cultural Organization (UNESCO) Women in Science Foundation, ARC Centre of Excellence for Coral Reef Studies, James Cook University (JCU), Laboratoire d'Excellence CORAIL, Station d'Ecologie Espérimentale of the Centre de Recherches Insulaires et Observatoire de l'Environnement (CRIOBE), French Ministère de l'Environnement, Australian Government Research Training Program
Projects and Grants: ARC Early Career Discovery Fellowship PDE150101266, L'Oréal-United Nations Educational, Scientific and Cultural Organization (UNESCO) Women in Science Foundation Fellowship (2015–16), Australian Government Research Training Program Scholarship
Date Deposited: 28 Nov 2018 08:56
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060203 Ecological Physiology @ 50%
05 ENVIRONMENTAL SCIENCES > 0501 Ecological Applications > 050101 Ecological Impacts of Climate Change @ 50%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 100%
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