Repeated, long-distance migrations by a philopatric predator targeting highly contrasting ecosystems

Abstract

Long-distance movements of animals are an important driver of population spatial dynamics and determine the extent of overlap with area-focused human activities, such as fishing. Despite global concerns of declining shark populations, a major limitation in assessments of population trends or spatial management options is the lack of information on their long-term migratory behaviour. For a large marine predator, the tiger shark Galeocerdo cuvier, we show from individuals satellite-tracked for multiple years (up to 1101 days) that adult males undertake annually repeated, round-trip migrations of over 7,500 km in the northwest Atlantic. Notably, these migrations occurred between the highly disparate ecosystems of Caribbean coral reef regions in winter and high latitude oceanic areas in summer, with strong, repeated philopatry to specific overwintering insular habitat. Partial migration also occurred, with smaller, immature individuals displaying reduced migration propensity. Foraging may be a putative motivation for these oceanic migrations, with summer behaviour showing higher path tortuosity at the oceanic range extremes. The predictable migratory patterns and use of highly divergent ecosystems shown by male tiger sharks appear broadly similar to migrations seen in birds, reptiles and mammals, and highlight opportunities for dynamic spatial management and conservation measures of highly mobile sharks.

Philopatry and Regional Connectivity of the Great Hammerhead Shark, Sphyrna mokarran in the U.S. and Bahamas

“…Such annual reuse of particular areas has long been documented across the animal kingdom, including sea turtles (Schofield et al, 2010), bats (Hillen et al, 2009) and birds (Blackburn and Cresswell, 2016), and is emerging as a widespread behavior for large-bodied coastal and oceanic sharks (Chapman et al, 2015). For example, tiger (Galeocerdo cuvier), lemon and oceanic whitetip sharks tracked in the same region exhibited, repeated migratory philopatry to overwintering sites (HoweyJordan et al, 2013;Kessel et al, 2014a;Lea et al, 2015). For the latter two species, the authors concluded that enhanced feeding opportunities and thermal conditions were the likely driver of the aggregations.…”

“…The idea that a portion of a population remains resident while the other migrate, known as partial migration, is a common phenomenon across the animal kingdom . It has recently been suggested for some highly mobile shark species including tiger and bull sharks (Carcharhinus leucas) (Papastamatiou et al, 2013;Lea et al, 2015;Espinoza et al, 2016) with important implications for management and conservation. Further, Grubbs and Kraus (2010) demonstrated differential migration in the highly migratory and highly exploited sandbar shark, Carcharhinus plumbeus where partial migration is sex, age and maturity dependent.…”

Ocean-wide tracking of pelagic sharks reveals extent of overlap with longline fishing hotspots

“…The shortfin mako Isurus oxyrinchus is the second most frequently caught species on Atlantic longlines, making up approximately 20% of pelagic shark catches (7). The tiger shark Galeocerdo cuvier is also known to migrate seasonally into oceanic habitats (19) that are exploited by high seas longliners, whereas coastal/pelagic hammerhead sharks (Sphyrna mokkaran and Sphyrna lewini) probably overlap with fishers exploiting the continental shelf (20).…”

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

“…This behavior has been observed in female nurse sharks, which have shown both avoidance and shallow water refuging from males (Pratt & Carrier 2001). While the mating and parturition behavior of tiger sharks visiting Tiger Beach is currently unknown, Lea et al (2015) reported that mature male tiger sharks tagged off Bermuda migrated to Bahamian waters during the winter months, leading the authors to speculate that their presence in the area was linked with mating. This coincides with the period when the highest proportion of mature females as well as those individuals with mating scars were observed at Tiger Beach.…”