Habitat geography around Hawaii’s oceanic islands influences tiger shark (Galeocerdo cuvier) spatial behaviour and shark bite risk at ocean recreation sites

Abstract

We compared tiger shark (Galeocerdo cuvier) spatial behaviour among 4 Hawaiian Islands to evaluate whether local patterns of movement could explain higher numbers of shark bites seen around Maui than other islands. Our sample consisted of 96 electronically-tagged (satellite and acoustic transmitters) tiger sharks, individually tracked for up to 6 years. Most individuals showed fidelity to a specific ‘home’ island, but also swam between islands and sometimes ranged far (up to 1,400 km) offshore. Movements were primarily oriented to insular shelf habitat (0–200 m depth) in coastal waters, and individual sharks utilized core-structured home ranges within this habitat. Core utilization areas of large tiger sharks were closer to high-use ocean recreation sites around Maui, than around Oahu. Tiger sharks routinely visited shallow ocean recreation sites around Maui and were detected on more days overall at ocean recreation sites around Maui (62–80%) than Oahu (<6%). Overall, our results suggest the extensive insular shelf surrounding Maui supports a fairly resident population of tiger sharks and also attracts visiting tiger sharks from elsewhere in Hawaii. Collectively these natural, habitat-driven spatial patterns may in-part explain why Maui has historically had more shark bites than other Hawaiian Islands.

A Perspective on Future Tiger Shark Research

“…Tester unpublished data). These observations, in conjunction with a single observation of a failed mating attempt by a camera-equipped male tiger shark in coral reef habitat (Meyer et al, 2018), suggest shallow coastal areas are mating habitats for Hawaii tiger sharks. There are currently no similar data from other parts of the world.…”

“…The seasonal timing of tiger shark mating is evident from mating scars on females (e.g., Whitney and Crow, 2007), but very little is known about the nature of mating behavior (see Meyer et al, 2018) or whether or not there are specific mating sites. Tiger sharks seem to be generally solitary, so finding a mate may be challenging unless there are specific locations and times when mating occurs.…”

“…Tiger sharks seem to be generally solitary, so finding a mate may be challenging unless there are specific locations and times when mating occurs. Within the main Hawaiian Islands, the probability of migration between islands for both adult male and female tiger sharks peaks during the winter mating season as does CPUE for adult males in shallow coastal habitats (Papastamatiou et al, 2013;Meyer et al, 2018;A. Tester unpublished data).…”

“…This dual internal/external tag technology has been successfully used to detect feeding behavior in several marine species including seals (e.g., Skinner et al, 2014). Similarly, equipping mature males with camera and depth and light level sensor packages during mating season (e.g., Meyer et al, 2018) would be the most direct path to elucidating the location and nature of mating behavior.…”

“…Satellite telemetry (Lea et al, 2015;Meyer et al, 2018) and catch records (Polovina and Lau, 1993;Domingo et al, 2016) show tiger sharks make offshore migrations in both the Pacific and Atlantic. Adult tiger sharks in the Atlantic undertake repeated annual migrations which track latitudinal shifts in sea surface temperatures (SST) (Lea et al, 2015(Lea et al, , 2018.…”