Hunt warm, rest cool: bioenergetic strategy underlying diel vertical migration of a benthic shark

Abstract

Summary1. 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. 2. 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. 3. 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. 4. 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. 5. 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.

Reef-use and residency patterns of a baited population of silky sharks, Carcharhinus falciformis, in the Red Sea

“…This finding is consistent with other aspects of shark behaviour found to exhibit diel periodicity, e.g. diving (Weng and Block 2004;Sims et al 2005;Rowat et al 2007) and feeding (Sims et al 2006). Although the diurnal bias of tagged sharks was apparent across all sites, the most pronounced disparity in time spent between day and night was at SP.…”

Year‐round sexual harassment as a behavioral mediator of vertebrate population dynamics

“…All tags were placed intraperitoneally (for detailed methodologies, see Sims et al 2006). Archival tags recorded swimming depth every 10 min for up to 1 year, whereas acoustic tags monitored horizontal movements for up to 2 years by recording presence within the vicinity (;200 m detection radius; Wearmouth 2006) of acoustic receiver stations (VR2, Vemco, Canada) moored in nonoverlapping locations in open seabed habitats and outside a female refuge (G1) (see Fig.…”

Short-term movements and diving behaviour of satellite-tracked blue sharks Prionace glauca in the northeastern Atlantic Ocean

“…Recent examples indicate significant shifts in movement patterns, diving behaviour and thermal biology in Atlantic bluefin tuna at different stages of the breeding cycle ), whilst abrupt changes were observed in the swimming behaviour of individual white sharks Carcharodon carcharias (Bruce et al 2006) and in the depth use of basking sharks Cetorhinus maximus (Shepard et al 2006). Knowing how individual behaviour varies across a range of spatio-temporal scales is an essential step towards understanding habitat selection processes in large marine animals (Sims et al 2006a). Habitat use is a necessary prerequisite for predicting the movements and distribution of marine species in relation to environmental change, which is critical for the development of management and conservation plans (McMahon & Hays 2006).…”