Researchers in Indonesia have completed a 14-month study of the Raja Ampat epaulette shark (Hemiscyllium freycineti), a walking shark species found only in the Raja Ampat Archipelago, providing the first comprehensive look at its biology and ecology. Scientists conducted 64 nighttime surveys across six locations in the Dampier Strait region during low tide, searching shallow reef flats, seagrass meadows, mangroves, and sandy habitats using headlamps and flashlights. The field work produced 1,191 shark sightings representing 736 unique individuals, revealing relative population densities ranging from 333 to 2,462 individuals per square kilometer.
Survey Results and Habitat Use in Indonesia
The survey effort documented remarkably high population densities, particularly around Arborek Island and Sawinggrai. Despite these numbers, researchers found that Raja Ampat epaulette sharks are strict homebodies with an extremely limited geographic range. Out of 256 re-encountered individuals, not a single shark was observed moving between study sites, and the greatest net displacement recorded was only 475 meters. The study also revealed ontogenetic habitat partitioning, where coral reefs function as nurseries containing nearly 70 percent immature juvenile sharks, while seagrass beds and sandy areas harbor larger proportions of adults.
Did You Know? The Raja Ampat epaulette shark evolved less than two million years ago and is found nowhere else on Earth outside of the waters surrounding Indonesia’s Raja Ampat Archipelago.
Growth, Reproduction, and Conservation Pressures
Data gathered on growth and reproduction showed a significantly female-biased population where females slightly outnumbered males. Individuals ranged from just under 8 to 29.5 inches (20 to 75 centimeters) in length, with both sexes reaching maturity at roughly 22 inches (56.5 centimeters). Young sharks grew much faster at nearly 3 inches (8 centimeters) per year compared to less than 1.2 inches (3 centimeters) annually for adults, showing seasonal fluctuations linked to monsoon-driven oceanography. Although the species received full legal protection in Indonesia in 2023 and is listed as Near Threatened, researchers note that its dependence on shallow coastal habitats makes it vulnerable to tourism development, habitat degradation, pollution, and climate change.
Expert Insight: Baseline studies of localized, site-faithful marine species are critical for effective wildlife management. When an animal’s home range is measured in meters rather than oceans, local habitat health dictates survival, meaning legal protections must be paired with active preservation of interconnected nursery and adult environments.
Frequently Asked Questions
What is the geographic range of the Raja Ampat epaulette shark?
The species is found exclusively in the waters surrounding Indonesia’s Raja Ampat Archipelago.
How far do Raja Ampat epaulette sharks typically travel?
Researchers observed extremely limited movement, with the greatest net displacement recorded being only 475 meters and no sharks observed moving between study sites.
What protections currently exist for the species?
The Raja Ampat epaulette shark received full legal protection in Indonesia in 2023, and the species is currently listed as Near Threatened.
How might rapid coastal environmental changes impact marine species that exhibit strict site fidelity?
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