Long-term movement patterns of tiger sharks Galeocerdo cuvier in Hawaii

Abstract

Little is known about the long-term movement patterns of most marine apex predators. A network of acoustic receivers was used to quantify the long-term movements of transmitterequipped tiger sharks Galeocerdo cuvier Péron & Lesueur, 1822 in the Main Hawaiian Islands. Tiger sharks were wide-ranging, swam between islands and patrolled up to 109 km of contiguous coastline. Visits to specific acoustic receiver sites were typically brief (mean duration 3.3 min), unpredictable and interspersed by absences of weeks, months or years. This pattern may be an optimal foraging strategy for capturing risk-averse prey. Tiger sharks may have to move on soon after arriving in an area because the element of surprise is quickly lost and potential prey become wary and difficult to catch. Juvenile tiger sharks were significantly wider-ranging and less frequently detected than mature females. Juveniles may be avoiding predation by larger individuals, or exploring to find suitable home ranges. Tiger sharks may also switch movement patterns and foraging strategies to take advantage of different prey types, restricting their movements to exploit seasonally abundant and naïve prey. Further empirical studies are required to directly link movement patterns with foraging.

Sizing up the ecological role of sharks as predators

“…Protection of reef communities through marine protected areas (MPAs) or fisheries regulation (or indeed, naturally on those few locations far from human population centres) would ensure the mesopredator sharks on these reefs are sheltered from fishing pressure. However, the same may not be true for apex predators because their broad movement patterns and large home ranges (Meyer et al 2009) would expose them to a greater diversity of fishing fleets and gears, and thus a greater overall mortality than the smaller-ranging, reef-dwelling mesopredators. Hence, the apex predators of coral reefs may be silently eliminated by offshore pelagic longline fisheries, unbeknownst to those managing reef diversity and function (Cox et al 2002).…”

Telemetry and random‐walk models reveal complex patterns of partial migration in a large marine predator

“…In high-latitude locations such as Australia, tiger sharks demonstrate seasonal utilization of bays within larger home ranges, with water temperature being a likely driver of seasonal habitat use (Wirsing et al 2006, Heithaus et al 2007). However, within tropical areas with milder seasonal changes in environmental characteristics, tiger shark movements appear more ambiguous (e.g., Meyer et al 2009a). Within the Hawaiian archipelago, individual tiger sharks will frequently swim between islands of the chain using straight directed walks, although their movements lack any clear overall pattern, seasonal or otherwise (Meyer et al 2009a.…”

Seasonal and life-stage variation in the reproductive ecology of a marine apex predator, the tiger shark Galeocerdo cuvier, at a protected female-dominated site

“…Given the considerable variation in both tiger shark growth rates (e.g. Meyer et al 2009) and size at maturity (260 to 347 cm TL; Whitney & Crow 2007, this study), we recognize that there is a certain level of uncertainty surrounding the designations as used in the current study. However, we believe our thorough review of the literature along with the data from Phase II sharks justifies our use of 300 cm as an appropriate length at maturity in the sampled sharks.…”

“…Although primarily a wide-ranging oceanic species, it also occupies a variety of other habitats, including coral reefs, pelagic environments, and oceanic atolls (Heithaus et al 2007, Meyer et al 2009, Fitzpatrick et al 2012, Hazin et al 2013, Papastamatiou et al 2013, Werry et al 2014). In the western central Atlantic, there is a shallow-water area on Little Bahama Bank nicknamed 'Tiger Beach' by dive tourism operators due to the high abundance of tiger sharks found there (Gallagher & Hammerschlag 2011).…”