April saw the sixth successful annual research cruise to study oceanic whitetip sharks at Cat Island. Since 2011, the Shark Research and Conservation Program, along with long-term collaborators Microwave Telemetry Inc (www.microwavetelemetry.com), Stony Brook University, University of North Florida, and Florida International University, have worked closely to answer a number of questions pertaining to the life-history and behavior of a known oceanic whitetip shark aggregation at Cat Island, The Bahamas. The project is supported and co-funded by Blue Ocean Institute, Save Our Seas Foundation, and the Moore Bahamas Foundation.
Historically, oceanic whitetip sharks were naturally abundant, and a common apex predator across the tropical and sub-tropical western Atlantic. However in the past 50 years, whitetip populations have come under severe threat as a result of the global fin trade. Oceanic whitetips are now categorized as ‘critically endangered’ in the Western Atlantic by the International Union of the Conservation of Nature (IUCN). Despite these pressures, the biology and ecology of this species remains highly elusive, highlighting a critical need for collection of these data from a management and conservation perspective.
The goals of the study are to:
- Determine generalized movements and determine high-use areas of sharks in relation to the Bahamas shark sanctuary.
- Examine diving behavior through high resolution temperature and depth data.
- Investigate potential hormone markers to identify reproductive cycles.
- Examine prey-preference potential seasonal diet switches through tracing relative concentrations of Carbon and Nitrogen isotopes.
- Gather baseline genetics data which will be incorporated into fin-trade management, and will detect fins from Oceanic whitetips found in the Western Atlantic.
This year, over a six day cruise, the team captured and released a total of 15 oceanic whitetips, and attached pop-up satellite tags (PSAT’s) measuring archived temperature, depth and light levels(used to define location) to 12 females. The tags are pre-programmed to record for a desired deployment duration ranging from 14 days to 12 months before detaching from the animal. Once the tag detaches, a sub-set of archived data is transmitted to a satellite system, meaning the tag does not need to be recovered. The main focus of this year’s cruise was to tag confirmed pregnant (via ultrasound) and recaptured individuals, to identify hormone pregnancy markers, and potential pupping grounds.
Investigating these large knowledge gaps are intrinsic to the contemporary management of oceanic whitetip shark populations, and will provide novel insights into the biology and ecology of a severely threatened apex predator.
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