Movements and habitat use of reef manta rays off eastern Australia: offshore excursions, deep diving and eddy affinity revealed by satellite telemetry

Abstract

Manta rays (Manta spp.) are plankton-feeding elasmobranchs classified as vulnerable to extinction on the IUCN Red List for Threatened Species. Despite increasing public and scientific interest in manta rays, major knowledge gaps concerning their movement ecology and dispersal capabilities remain. Here, we used pop-off satellite-linked archival transmitting tags to examine the horizontal movements and habitat use patterns of reef manta rays (M. alfredi) departing Lady Elliot Island in the southern Great Barrier Reef, Australia. Tagged individuals moved across a latitudinal range of 1035 km, travelling up to 2441 km in 118 d, diving down to 294.5 m and venturing up to 155 km off the continental shelf. Using random walk simulations, we showed that manta rays spent significantly more time in an offshore region characterised by the mesoscale cyclonic Capricorn Eddy than would be expected by chance. A behaviour-switching state-space model suggested this area to be an important foraging ground for M. alfredi off eastern Australia. We document the movements of 1 individual using offshore waters between 2 known aggregation regions off eastern Australia. Reef manta rays thus not only occupy inshore continental shelf and shelf-edge waters but also use offshore environments to exploit productive hotspots and travel long distances. Our findings highlight the need to better understand their movement ecology for effective management.

Conservation challenges of sharks with continental scale migrations

“…A number of mobile species have been reported to move or migrate along the east coast of Australia. This includes coastal residents such as turtles and dugongs (Limpus et al, 1992;Zeh et al, 2015), seasonal migrators such as humpback whales (e.g., Rock et al, 2006) and pelagic species such as marlin and manta rays (Gunn et al, 2003;Jaine et al, 2014). Movements of many of these species can be attributed to biological needs or access to resources.…”

“…Movements of many of these species can be attributed to biological needs or access to resources. For example, manta ray movements have been correlated with oceanographic conditions such as eddies which may enhance foraging opportunities (Jaine et al, 2014). Black marlin also showed movement based on environmental conditions with individuals displaying distinct preferences for the mixed layer and specific temperatures (Gunn et al, 2003).…”

“…There are a number of marine species that undertake large movements with varying levels of understanding of the timing and location of these moves. Coastal marine mammals, reptiles, and fishes can undertake extensive oceanic and continental-scale movements related to biological requirements and resource needs (e.g., Limpus et al, 1992;Block et al, 2011;Hays et al, 2014;Jaine et al, 2014;Zeh et al, 2015). Sharks and rays represent one of the most diverse groups of large marine predators, and as such represent important functional groups within marine ecosystems.…”

Movements of the reef manta ray (Manta alfredi) in the Red Sea using satellite and acoustic telemetry

“…However, despite their iconic status and value to tourism, some key questions still remain, and no studies have quantified manta ray movements in the Red Sea. Photo-identification and telemetry techniques elsewhere have provided evidence of both site fidelity (e.g., Dewar et al 2008) and large-scale movements (>2400 km) by reef mantas (Jaine et al 2014). By coupling acoustic technology with satellite tracking, we provide further evidence of site affinity by reef mantas and corroborate existing evidence that manta ray movements may be rather limited when compared to other large planktivorous elasmobranchs (e.g., Skomal et al 2009;Sequeira et al 2013), including at least one other species of mobulid ray (Mobula tarapacana) in the North Atlantic .…”

First photographic records of the giant manta ray Manta birostris off eastern Australia

“…Manta birostris is considered a more oceanic and migratory species, and is found predominantly in cooler, temperate to subtropical waters (Marshall et al 2011a). Manta alfredi displays a high degree of site fidelity in tropical and subtropical waters, but may also undertake local to regionalscale (>700 km) movements and seasonal migrations Couturier et al 2011;Deakos et al 2011;Dewar et al 2008;Jaine et al 2014;Marshall et al 2011b). …”