Tractable models for testing theories about natural strategies: foraging behaviour and habitat selection of free‐ranging sharks

Abstract

Marine and terrestrial environments differ fundamentally in space-time scales of both physical and ecological processes. These differences will have an impact on the animals inhabiting each domain, particularly with respect to their spatial ecology. The behavioural strategies that underpin observed distributions of marine species are therefore important to consider. Comparatively little is known, however, about how wild fishes actually respond to gradients in food supply and temperature, and to potential mates. This paper describes how behavioural theory is being used to elucidate the strategies and tactics of free-ranging sharks in three specific areas of study, namely, foraging on zooplankton, behavioural energetics and sexual segregation. The studies discussed are novel because shark movements were tracked in the wild using electronic tags in relation to simultaneous measurements of prey densities and thermal resources. The results show that filter-feeding (basking shark, Cetorhinus maximus) and predatory (dogfish, Scyliorhinus canicula) sharks have relatively complex behaviour patterns integrally linked to maximizing surplus power, often through making short and longer term 'trade-off' decisions between optimal foraging and thermal habitats. Interestingly, female S. canicula exhibit alternative behavioural strategies compared to males, a difference resulting in spatial segregation by habitat. Sexual segregation in this species occurs primarily as a consequence of male avoidance by females. Studies on free-ranging sharks provide a useful model system for examining how a predator's strategy is shaped by its environment. More theory-based studies of the behavioural processes of sharks are required however, before critical comparisons with other vertebrate predators are possible. Suggestions for further research to address this knowledge gap are given.

Complexities of coastal shark movements and their implications for management

“…The ontogenetic or species segregation of individuals is common in sharks (Springer 1967), particularly in coastal carcharhinids (Castro 1993), and could have evolved as a consequence of competition for resources or predation (Sims 2003). Such behaviour can also be a reflection of differing physiological tolerances to environmental conditions (see 'Habitat specificity' above).…”

“…This behaviour often occurs due to physical and biotic requirements of animals, which in turn determine habitat selection. Therefore, to understand how fishes distribute themselves, quantifying which habitats they choose, when they choose them and why needs addressing (Sims 2003). The potential importance of physical and biotic factors in habitat selection by sharks has been reviewed by Simpfendorfer & Heupel (2004) and has been addressed by approximately 75% (n = 79) of the studies included in our review (Table S1 in the supplement).…”

“…The movement of whale sharks is also influenced by geostrophic currents (Rowat & Gore 2007), in contrast to scalloped hammerhead sharks whose swimming is unaffected by current direction (Klimley & Nelson 1984). Sims (2003) noted that one of the main factors determining animal distribution patterns and therefore, habitat selection, is the relative abundance and availability of suitable prey. This idea is supported by evidence from sharks at opposing trophic levels such as tiger (Heithaus et al 2002, Wirsing et al 2007) and basking sharks (Sims & Quayle 1998).…”

Effects of acute and chronic temperature changes on the functional responses of the dogfish Scyliorhinus canicula (Linnaeus, 1758) towards amphipod prey Echinogammarus marinus (Leach, 1815)

“…We investigated predation by juvenile Scyliorhinus canicula (lesser-spotted dogfish) on amphipod prey Echinogammarus marinus. Both species are ubiquitous in temperate waters (Ellis and Shackley 1997;Duffy and Harvilicz 2001), resilient (Múrias et al 1996;Revill et al 2005;Leite et al 2014) and pliable laboratory species (Sims 2003). These are ecologically relevant species as E. marinus has large impacts upon community structuring (Duffy and Hay 2000;Dick et al 2005), and is an important prey species (Leite et al 2014) that can additionally be considered a proxy for other small crustacean species and small fish due to strong swimming behaviours.…”

Spatial and temporal movement patterns of a multi-species coastal reef shark aggregation

“…However, few studies have quantified temporal and spatial habitat partitioning among different species, although there is some evidence to support inter-specific partitioning in relation to the distribution of prey (White & Potter 2004), habitat type and season (White & Potter 2004, DeAngelis et al 2008. The underlying processes determining this partitioning and segregation are often related to predator avoidance and the reduction of intra-and inter-specific resource competition (Sims 2003). However, the mechanisms that allow different species and several size classes of the same species to coexist are often unclear; therefore, more species and systems need to be investigated to provide insight and to assist in management of multi-species complexes (Speed et al 2010).…”