Sims, David W., Wearmouth, Victoria J., Southall, Emily J., Hill, Jaqueline M., Moore, Pippa, Rawlinson, Kate, Hutchinson, Neil, Budd, Georgina C., Righton, Dave, Metcalfe, Julian, Nash, Jon, and Morritt, David (2006) Hunt warm, rest cool: bioenergetic strategy underlying diel vertical migration of a benthic shark. Journal of Animal Ecology, 75 (1). pp. 176-190.

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Abstract

Diel vertical migration (DVM) is a widespread phenomenon among marine and freshwater organisms and many studies with various taxa have sought to understand its adaptive significance. Among crustacean zooplankton and juveniles of some fish species DVM is accepted widely as an antipredator behaviour, but little is known about its adaptive value for relatively large-bodied, adult predatory fish such as sharks. Moreover, the majority of studies have focused on pelagic forms, which raises the question of whether DVM occurs in bottom-living predators.

To investigate DVM in benthic predatory fish in the marine environment and to determine why it might occur we tracked movements of adult male dogfish (Scyliorhinus canicula) by short- and long-term acoustic and archival telemetry. Movement studies were complemented with measurements of prey abundance and availability and thermal habitat within home ranges. A thermal choice experiment and energy budget modelling was used to investigate trade-offs between foraging and thermal habitat selection.

Male dogfish undertook normal DVM (nocturnal ascent) within relatively small home ranges (∼100 × 100 m) comprising along-bottom movements up submarine slopes from deeper, colder waters occupied during the day into warmer, shallow prey-rich areas above the thermocline at night. Few daytime vertical movements occurred. Levels of activity were higher during the night above the thermocline compared to below it during the day indicating they foraged in warm water and rested in colder depths.

A thermal choice experiment using environmentally realistic temperatures supported the field observation that dogfish positively avoided warmer water even when it was associated with greater food availability. Males in laboratory aquaria moved into warm water from a cooler refuge only to obtain food, and after food consumption they preferred to rest and digest in cooler water.

Modelling of energy budgets under different realistic thermal-choice scenarios indicated dogfish adopting a 'hunt warm − rest cool' strategy could lower daily energy costs by just over 4%. Our results provide the first clear evidence that are consistent with the hypothesis that a benthic marine-fish predator utilizes DVM as an energy conservation strategy that increases bioenergetic efficiency.

Item ID:	45434
Item Type:	Article (Research - C1)
ISSN:	1365-2656
Keywords:	behavioural ecology, electronic tags, energetics, fish, thermocline
Funders:	UK Natural Environment Research Council (NERC), Fisheries Society of the British Isles, British Ecological Society, Jubilee Trust, Percy Sladen Memorial Trust
Projects and Grants:	NERC NER/A/S/2001/01053
Date Deposited:	01 Sep 2016 02:21
FoR Codes:	06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 50% 06 BIOLOGICAL SCIENCES > 0608 Zoology > 060801 Animal Behaviour @ 50%
SEO Codes:	96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 100%
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