The sliteye shark (Loxodon macrorhinus), a species recognized for its unique slit-shaped eyes designed for enhanced vision in low-light settings, has been documented for the first time on the Great Chagos Bank. This remarkable coral atoll, known as the largest of its kind globally, represents a significant milestone in marine biology, expanding the known habitat range of this near-threatened species. The recent discovery uncovers new ecological layers in the biodiversity of the Chagos Archipelago, underscoring the immense value of its marine ecosystems, particularly the deepwater seagrass meadows.
The presence of the sliteye shark within these underexplored seagrass ecosystems takes on even greater importance against the backdrop of the Chagos Archipelago’s role as a Marine Protected Area. This designation aims to preserve the region’s biodiversity hotspots, which until recently remained poorly understood. Scientists employing Baited Remote Underwater Video (BRUV) technology—an innovative non-invasive method that lures marine wildlife for observation without human interference—captured footage of these elusive sharks. The sharks were located at depths ranging from 23 to 29 meters along the bank’s southern rim, specifically in seagrass meadows previously unknown to researchers.
The distinctive eyes of the sliteye shark provide a crucial evolutionary advantage by allowing the species to thrive in both dimly lit, deeper marine environments and clearer, shallower waters. This adaptability sheds light on the shark’s broad ecological niche and its behavioral patterns, which had not been thoroughly documented in the Indian Ocean until now. The discovery of these individuals, recorded just 11 kilometers apart, suggests a potentially robust population utilizing these obscure habitats, though ongoing research is required to ascertain population dynamics within the region.
The ecological importance of deepwater seagrass habitats, only identified by this research team in 2016, cannot be overstated. Seagrass meadows function as vital underwater forests that offer shelter, breeding grounds, and foraging opportunities for a remarkable diversity of marine life. Within the Great Chagos Bank, these meadows occur at extraordinary depths compared to global norms. The association of sliteye sharks with these habitats indicates a complex ecosystem where predator-prey relationships and biodiversity might be richer than previously anticipated.
Research efforts led by Swansea University’s Marine and Conservation Ecology Lab emphasize that while the sliteye shark has a wide geographical distribution ranging across the Indo-Pacific, the new data from Chagos fills a critical knowledge gap. Marine ecologist Charlotte Oulton, spearheading the study, reflects on how this finding highlights both the enigmatic nature of deep-sea ecosystems and the urgent need to deepen scientific investigation into these environments. The discovery encourages broader surveillance of the seagrass beds as reservoirs of marine biodiversity, particularly within the isolated and pristine environs of the Indian Ocean.
Parallel studies involving satellite tracking of endangered green turtles (Chelonia mydas) have serendipitously revealed the existence of these extensive seagrass meadows. Operating at depths previously deemed atypical for such vegetative assemblages, these seagrass beds span large swathes of the Great Chagos Bank and sustain an array of marine species hitherto undocumented in these locales. Over 110 fish species have been identified using the seagrass as critical habitats for food and refuge, reinforcing the ecosystem’s ecological web complexity and resilience.
Considering that sliteye shark populations are estimated to face a decline of up to 29% over the next decade and a half—primarily due to fishing pressures—these findings inject new urgency into global conservation dialogues. Understanding the species’ habitat preferences and abundance within the Chagos Marine Protected Area helps shape management decisions aimed at mitigating exploitation risks. Moreover, the observations endorse the necessity to safeguard deepwater environments that remain largely enigmatic yet are evidently pivotal for numerous species’ lifecycles.
The current research, conducted in the closing months of 2024, constitutes a collaborative synergy between Swansea University and international academic and conservation organizations. It benefits from funding by the Bertarelli Foundation, particularly through their Indian Ocean Marine Science Programme, which seeks to enhance scientific comprehension and protection of marine ecosystems in this strategically vital oceanic region. This partnership underscores the critical role of multidisciplinary international cooperation in tackling challenges related to marine biodiversity loss.
Future research trajectories include meticulous mapping of seagrass distribution across the Archipelago to determine its spatial coverage accurately. Concurrently, ecological niche modeling and habitat suitability predictions will clarify the environmental parameters driving seagrass proliferation, guiding conservation actions and resource allocation. These efforts aim to build robust frameworks that integrate habitat conservation with sustainable marine resource use, particularly in the face of climate change and increasing anthropogenic impacts.
Detailed examination of ecological interactions within this seagrass matrix strives to reveal the trophic dynamics and habitat dependencies of associated marine fauna, including the sliteye shark. Such comprehensive knowledge is essential for refining biodiversity indicators and informing policy decisions surrounding Marine Protected Area management. It further enables the identification of critical habitats and biodiversity hotspots, assisting in prioritizing areas for stricter protection or restoration initiatives.
The sliteye shark discovery symbolizes a frontier in marine ecological research, demonstrating how innovative survey methods and exploration of remote habitats can transform our understanding of species distributions. It challenges previous assumptions about the limited biodiversity potential of deepwater seagrass beds and fuels optimism that other undiscovered or poorly understood marine communities exist, especially in isolated oceanic regions.
A complete synthesis of the ongoing research outcomes is anticipated by 2026, promising to augment current ecological databases and conservation paradigms. These findings will undeniably contribute to shaping future marine biodiversity conservation strategies not only in the Indian Ocean but potentially in similar coral atoll ecosystems worldwide, where deepwater seagrasses conceal complex biological assemblages.
The unveiling of the sliteye shark within the Great Chagos Bank’s deepwater seagrass biomes stands as a testament to the ocean’s still hidden diversity. It reaffirms the need for continued and expanded scientific inquiry into understudied marine habitats and exemplifies the profound ecological insights gained when technology, keen observation, and international collaboration converge in the quest to preserve our planet’s underwater heritage.
Subject of Research: Marine biodiversity and ecology focusing on the sliteye shark within deepwater seagrass habitats in the Great Chagos Bank.
Article Title: Sliteye Shark Discovery Expands Understanding of Deepwater Seagrass Ecosystems in the Great Chagos Bank
News Publication Date: Late 2024
Web References:
- Sliteye shark IUCN Red List: https://dx.doi.org/10.2305/IUCN.UK.2021-2.RLTS.T41831A173435173.en
- Marine Protected Area in Chagos: https://doi.org/10.1007/s00227-020-03776-w
- Deepwater seagrass habitats research: https://doi.org/10.1016/j.marpolbul.2018.03.018
- Bertarelli Foundation’s Indian Ocean Marine Science Programme: https://www.fondation-bertarelli.org/marine/marine-science/
References:
Charlotte Oulton et al., Swansea University Marine and Conservation Ecology Lab (2024 ongoing studies)
Dr. Nicole Esteban, Swansea University Marine Ecology (Satellite tracking and seagrass study)
Image Credits: Charlotte Oulton
