Epaulette Sharks as an Indicator Species for Climate Change: Current Knowledge & Future Directions
Carolyn Wheeler
Biography: Carolyn is a co-tutelle PhD student between the School for the Environment at the University of Massachusetts Boston and the ARC Centre of Excellence for Coral Reef Studies at James Cook University. Carolyn spent the first half of her PhD working with the Anderson Cabot Center for Ocean Life at the New England Aquarium in Boston studying the effects of temperature on development and physiological performance of epaulette shark embryos and hatchlings. She then received a graduate fellowship through the American Australian Association to continue her research at JCU assessing the impacts of thermal stress on reproduction in adult epaulette sharks.
Epaulette sharks as an indicator species for climate change: Current knowledge and future directions
Carolyn R. Wheeler (1,2,3), Connor R. Gervais (4), John Mandelman (2,3), Jodie L. Rummer (1)
1. ARC Centre of Excellence for Coral Reef Studies; James Cook University; Townsville QLD, AUS
2. School for the Environment; The University of Massachusetts Boston; Boston MA, USA
3. Anderson Cabot Center for Ocean Life; New England Aquarium; Boston MA, USA
4. Macquarie University; Sydney NSW, AUS
Abstract: Elasmobranchs (sharks, rays, and skates) play a key role in structuring marine ecosystems and indirectly protect habitat and food security for humans. For most of these species, we do not know if and through which mechanisms they can survive impending climate change stressors like ocean warming and acidification. Furthermore, roughly 40% of all elasmobranchs are oviparous, meaning that embryos undergo part of their development within an egg case on the ocean floor where they are restricted to and potentially vulnerable to the surrounding environmental conditions. The epaulette shark (Hemiscyllium ocellatum), a small oviparous shark endemic to the Great Barrier Reef, has been the focus of many climate change related laboratory studies by our research group because this species thrives in captivity and is considered of least concern by the International Union for the Conservation of Nature (IUCN). Additionally, this shark species is considered resilient to abiotic conditions, such as elevated carbon dioxide (CO2) and hypoxia (low oxygen, O2), and we propose this shark could serve as a conservative indicator species for elasmobranchs that are more sensitive to environmental change or logistically difficult to study. In other words, if epaulette sharks cannot cope with future climate change conditions, how will less-tolerant elasmobranch species fare? Here, we synthesize six years of findings to outline our current knowledge base and discuss key studies that are in progress. Broadly, ocean acidification conditions – alone – do not dramatically impact growth and development in embryos or neonates or physiological performance and foraging behaviours in adults. This species is also noted as the most hypoxia-tolerant elasmobranch studied to date. However, ocean warming scenarios (i.e., temperatures in the tropics at or exceeding 31°C) heavily impact growth, development, and physiological performance in this species. Today, our research aims to the effects of chronic thermal stress on the reproductive biology and endocrinology of adult epaulette sharks. Overall, we recommend epaulette sharks as a physiological indicator species for the ~400 species of oviparous elasmobranchs, particularly those native to tropical regions. Outcomes will prove important toward conservation and management efforts, where the degree of sensitivity to climate change is key for vulnerability assessments.
Banner Photo: Samantha Aird