Reproductive timing and putative mating behavior of the oceanic whitetip shark Carcharhinus longimanus in the eastern Bahamas

Abstract

Oceanic whitetip sharks Carcharhinus longimanus aggregate at Columbus Point, Cat Island, The Bahamas, in at least April and May. We show that signs of putative mating activity (i.e. bite wounds) on mature females, which dominate the aggregation, are exceedingly rare at that time, but may be more common in July. Male plasma testosterone concentrations also suggest that spermatogenesis occurs in April and May and copulation is underway or has just ended by July. We support these preliminary data with direct observations of putative precopulatory behavior made at Columbus Point in July 2019. Using 25 min of video footage from the event, we identify common shark mating behaviors such as echelon or parallel swimming, following, shielding, nosing, and biting. We also describe the ‘circle-back’, a newly observed behavior where the male orients to the trail of the female, possibly to investigate olfactory cues. Based on these 3 parallel lines of evidence, we hypothesize that mating could occur in the eastern Bahamas as early as May, but is probably concentrated in midsummer (i.e. July), and that Columbus Point, Cat Island, may be a mating habitat for the oceanic whitetip shark.

Insights into the Relative Abundance, Life History, and Ecology of Oceanic Sharks in the Eastern Bahamas

“…Indeed, oceanic predators can be attracted to foraging areas [94,95] where environmental characteristics (e.g., local bathymetry, ocean currents, on-shelf reef area [93]) enhance bottom-up processes [96,97] that attract potential prey [98,99]. For example, abundant pelagic teleost prey may attract wide-ranging oceanic whitetip sharks to CI in April-May, after which the high density of sharks may facilitate and coincide with mating in summer [21][22][23]. We encourage future research to clarify (1) temporal shifts in shark diversity, relative abundance, and demographic structure at apparent aggregation sites and (2) spatial variation in relative abundance between sites.…”

“…Some shelf-edge open-ocean habitats in the eastern Bahamas may serve as these habitats for wide-ranging oceanic and semi-pelagic sharks (as defined by [20]). For example, Critically Endangered (IUCN Red List of Threatened Species [15]) adult oceanic whitetip sharks aggregate off Columbus Point, Cat Island, The Bahamas (CI) in April-May, with at least 20% of individuals exhibiting multi-year site fidelity that may be motivated by abundant pelagic teleost prey in late spring [21] and/or mating in summer [22]. Satellite telemetry data revealed that oceanic whitetip sharks tagged at CI spent considerable time (24-100% of 31-245-day tag durations) within the Bahamian Exclusive Economic Zone (EEZ) [23], but sample size and inherent limitations of light-level based geolocation estimates precluded the fine-scale identification of high-use areas.…”