OverviewRecent advances in satellite tagging and tracking are allowing scientists to “spy” into the secret lives of marine animals. We are currently using satellite tags to track the movements of shark species in the subtropical Atlantic. The goal of this work is to understand the migratory routes and residency patterns of these sharks to identify “hot spots” in place and time that are critical for mating, giving birth and feeding as well as locations where these animals are vulnerable to destructive fishing. By characterizing and identifying these hot spots, we can help supply policy makers with the data they need to implement effective management strategies that will improve conservation for these species. Some of the major questions we are currently investigating include:
- What is the distribution and scale of seasonal movement patterns of Hammerhead, Bull, and Tiger Sharks in the subtropical Atlantic?
- Do these species exhibit site fidelity and/or habitat specialization and if so, is there evidence of inter- and intra-specific differences?
- To what extent is shark habitat use divided among different marine protected and political-economic zones?
- Are long-term and large-scale shark movements influenced by ecotourism activities?
- What areas are sharks most vulnerable to capture by longline fishing?
Recent Study Highlights & Selected Examples
In a paper published in the journal Functional Ecology titled, “Don’t bite the hand that feeds: Assessing ecological impacts of provisioning ecotourism on an apex marine predator,” our team and collaborators conducted a satellite tagging study to examine the long term and long range movement patterns of tiger sharks in response to dive tourism. The tracking data suggested that over large spatial and time scales, the long-distance migration patterns of the sharks did not appear to be impacted by dive eco-tourism. Tiger sharks tagged in Bahamas and Florida exhibited previously unknown long-distance migrations of up to 3500 km into the Atlantic. These migrations appeared to follow the Gulf Stream through areas of high productivity that concentrate shark prey, suggesting the movements may be linked to feeding forays. The video below is a visual overview of a paper we published in the Journal of Functional Ecology based on our satellite tagging research.
Figure (Above): Kernel volume contours for 11 tiger sharks in Florida, displaying core use regions determined from the satellite tracking data. Figure modified from Hammerschlag et al. Functional Ecology 26(3): 567-576
Image (Above): This is one of the satellite tags that SRC is currently using and testing in the field. These transmitters are capable of recording shark position as well as the water temperature and depth at which the animals are swimming.
Hammerschlag N, Luo J, Irschick DJ, Ault JS (2012) A Comparison of Spatial and Movement Patterns between Sympatric Predators: Bull Sharks (Carcharhinus leucas) and Atlantic Tarpon (Megalops atlanticus). PLoS ONE 7(9): e45958. doi:10.1371/journal.pone.0045958 Hammerschlag N, Gallagher AJ, Wester J, Luo J, Ault JS. 2012 (Cover). Don’t bite the hand that feeds: assessing ecological impacts of provisioning ecotourism on an apex marine predator. Functional Ecology, 26(3): 567-576 Hammerschlag N, Gallagher AJ, Lazarre DM. 2011. A Review of Shark Satellite Tagging Studies. Journal of Experimental Marine Biology and Ecology; 398(1-2): 1–8. Hammerschlag N, Gallagher AJ, Lazarre DM, Slonim C. 2011. Range extension of the endangered great hammerhead shark Sphyrna mokarran in the Northwest Atlantic: Preliminary data and significance for conservation; Endangered Species Research, 13: 111–116.
By evaluating current protection measures, as well as discovering areas of significant shark aggregations where they may be vulnerable to overfishing, we can provide policy makers with data that can be used to help implement effective strategies that maximize shark conservation while enabling sustainable fishing.