Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Biology

First Advisor's Name

Yannis Papastamatiou

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Michael Heithaus

Second Advisor's Committee Title

Committee Member

Third Advisor's Name

Jennifer Rehage

Third Advisor's Committee Title

Committee Member

Fourth Advisor's Name

Joel Trexler

Fourth Advisor's Committee Title

Committee Member

Fifth Advisor's Name

Elizabeth Babcock

Fifth Advisor's Committee Title

Committee Member

Keywords

abundance, accelerometry, acoustic telemetry, baited remote underwater video stations, behaviour, Caribbean, coral reefs, ecology, sharks, stingrays

Date of Defense

3-29-2023

Abstract

Shark declines may cause trophic cascades, which is partially dependent on how sharks influence prey abundance and behaviour. Rays are mesopredators that play a unique role in ecosystems as bioturbators. My dissertation investigates whether sharks induce changes in ray sightings, behaviour, and habitat use across multiple spatial and temporal scales. First, I reviewed the ray ecology literature and found limited evidence for risk-induced ray trait responses (Chapter 1). Next, using a baited remote underwater video station (BRUVS) survey, I found that southern stingray (Hypanus americanus) sightings were negatively associated with shark abundance throughout the tropical Western Atlantic Ocean (Chapter 2). Other important predictors of southern stingray sightings in the region included habitat complexity, geomorphology, and bottom fishing gear. At a smaller spatial scale inside the Glover’s Reef Marine Reserve in Belize, a BRUVS survey revealed southern stingray sightings and behaviour remained stable between 2009 – 2019 despite a concurrent decline in the relative abundance of Caribbean reef sharks (Carcharhinus perezi) (Chapter 3). Habitat complexity explained southern stingray sightings and behaviour on BRUVS, which may be due to their preference for soft bottom habitats and/or because we are less likely to detect stingrays on BRUVS in areas with high reef relief. Passive acoustic telemetry showed Caribbean reef and lemon (Negaprion brevirostris) sharks use shallow lagoon habitat, which was also the preferred habitat of southern stingrays, suggesting it is unlikely a refuge from predators. Finally, using accelerometry and hidden Markov models, I found that southern stingray activity is crepuscular and nocturnal, with high individual variation (Chapter 4). Southern stingrays were highly active in shallow water (m), which is likely associated with prey activity and availability. My findings emphasize the context dependent nature of predation risk effects and the need to take a multimethod approach to understand ray behaviour and habitat use.

Identifier

FIDC011036

ORCID

https://orcid.org/0000-0002-4354-2948

Previously Published In

Flowers KI, Heithaus MR, Papastamatiou YP (2021) Buried in the sand: Uncovering the ecological roles and importance of rays. Fish and Fisheries 22: 105 – 127.

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