2015 Expedition: Manta Ray Movement Patterns in PIPA

Aquarium researchers and staff are on expedition to the remote Phoenix Islands Protected Area (PIPA) to study the natural history of the islands, surrounding reefs and connecting open water ecosystems. Research on the 2015 expedition will directly inform the management and maintenance of this world-renowned MPA. Today's post comes from researchers Darren Coker.

Kanton Island is a relatively large atoll with an expansive and shallow lagoon. The single entrance to the lagoon provides the perfect playground for manta rays riding the currents as the lagoon fills and drains with the tides. Manta rays (Manta birostris) are threatened megafauna and in 2006 were listed as a Near Threatened species by the IUCN. The population at Kanton Island provides a unique opportunity to study these animals within a protected and geographically isolated area.

Manta ray in PIPA | Photo: Shawn Harper

The out flow of water from the lagoon contains nutrients that are re-suspended and washed out by the increased currents. To track the localized movement patterns of these large majestic rays within the island’s lagoon and fringing reefs, small acoustic tags are attached to the top of the ray. These tags emit a signal that is unique to each individual and received by a network of hydrophones (acoustic receivers) dotted around the island. Researchers ride the out going tides through the lagoon entrance on snorkel looking for manta rays. Once spotted, color patterns and size are noted before attaching the tag with the use of a hand spear. The tag is inserted into the thick dorsal muscle and aside from getting a fright the tag causes no harm. The tags can stay attached to the ray for several years, transmitting valuable data about their movements every few minutes.

Manta ray in PIPA | Photo: Shawn Harper

Little is known about manta ray movement patterns and what regions of the reef and lagoon are used. The movements of these manta rays will help us understand population connectivity and movement patterns around the islands. Movement and migration behavior of individuals can reveal key ecological characteristics and population dynamics of a species. This is particularly important for pelagic species that occur within the Phoenix Islands protection areas and beyond its boarders.

— Darren

Darren Coker, PhD, was born in New Zealand but spent some of his childhood in the Solomon Islands and England. His love of traveling later took him to Australia where he learned to dive on the Great Barrier Reef. Since then, Darren completed a Bachelor of Science in Marine Biology at James Cook University (JCU) and a PhD at the ARC Centre of Excellence for Coral Reef Studies (JCU) and the Australian Institute of Marine Science in Townsville, Australia. Following his PhD, Darren worked at the ARC Centre of Excellence for Coral Reef Studies investigating the effects of climate change on commercially important reef fishes. He joined the Reef Ecology Lab at KAUST as Postdoctoral Fellow in spring 2014. Darren’s research interests include investigating the importance of live coral habitats for fishes and how changes in habitat condition following disturbances impact the abundance, recruitment, and behavior of associated reef fishes. He is also investigating the role ecological processes play in biogeographic patterns of Red Sea reef fishes.

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