Wendy Wu ’22 

As a keystone species, sharks play a large role in maintaining a marine ecosystem. Unfortunately, climate change, habitat loss, and commercial fishing have led to sharp declines in shark populations around the world. To conserve and rebuild shark populations, many island nations have established marine protected areas (MPAs). The effectiveness of a MPA depends on whether it accommodates the species’ behavior and its ecological niche. Shark MPAs, however, have been constructed without proper understanding of shark behavior and habitat usage. As such, Oliver Shipley, a PhD student at the School of Marine and Atmospheric Sciences at Stony Brook University, conducted a study using acoustic telemetry to better understand the behavioral ecology of reef-associated shark species. 

From February 2018 to February 2020, the research team performed their study at a well-established shark sanctuary in The Bahamas, specifically in the coastal waters of New Providence Island and the island of Great Exuma. Twenty-three Caribbean reef sharks and 15 tiger sharks were captured for the study and implanted with acoustic transmitters. Thirteen acoustic receivers were then distributed across the two islands 5-18 meters underwater in seagrass, sand, and reef habitats. Shark detection data was collected and subsequently processed to remove false detections and animal mortalities. Further analysis was done to map out general movement patterns and factors influencing habitat use for both shark species. 

The researchers found that Caribbean reef sharks often preferred to return to one location, especially in coral reef habitats. In contrast, tiger sharks exhibited greater roaming behavior, moving between all habitat types, but especially to seagrass habitats. The team postulates that this is a result of predation of the smaller reef sharks by the larger tiger sharks; Caribbean reef sharks avoid the territories frequented by tiger sharks and prefer habitats with more escape routes. This provides insight into predator-prey interactions and the role large sharks play in an ecosystem. By roaming, tiger sharks connect habitats, transporting nutrients, and controlling prey populations. The variation in movement patterns and network-driven habitat use provides critical information in future establishment and monitoring of MPAs. In fact, this study suggests that large MPAs encompassing multiple habitat types may be more effective at conserving biodiversity than small, specifically-tailored MPAs. To improve MPA planning and building, current shark sanctuaries are great references for future studies into the biology and behavior of shark species.

Works Cited:

[1] A.J. Gallagher, et. al, Spatial connectivity and drivers of shark habitat use within a large marine protected area in the Caribbean, The Bahamas Shark Sanctuary. Frontiers in Marine Science, (2021). https://doi.org/10.3389/fmars.2020.608848.

[2] Image retrieved from: https://commons.wikimedia.org/wiki/File:Caribbean_reef_sharks_and_a_lemon_shark_.jpg.