How we tag and track mantas

Project Manta uses a variety of electronic tags to investigate broad scale migration and diving patterns as well as fine scale movements and behaviour. Electronic tags are fantastic tools for studying manta rays as they enable us to track individual animals remotely when it’s not possible to observe them directly in the water. In particular, tagging enables us to track mantas under difficult conditions, such as night time and rough seas, as well as to offshore locations where it’s not possible to follow them. Depending on the study different kinds of electronic tags are used. 

Acoustic tagging

Acoustic tags are small, individually coded tags that emit acoustic signals.  These tags are picked up by listening stations (receivers) that are deployed at strategic locations of interest.  Acoustic tags are attached to the manta via a dart head which is inserted into the dorsal (back) muscle of the manta using a hand spear.  The manta with the acoustic tag needs to swim near the listening station (approximately within 500 m depending on the reef structure) and when in the detection range, the station records the manta’s presence and decodes the tags to identify the individual.  Acoustic tags have been used by Project Manta to monitor large scale movements between key aggregation sites as well as fine scale behavioural studies around Lady Elliot Island.  Acoustic tags are an important research tool used by many researchers around Australia.  Acoustic data from Project Manta is uploaded onto the IMOS Animal Tracking data base and contributes to this nation-wide Australian initiative to assist in the long-distance tracking of migratory marine animals. 

Deploying acoustic listening station
Photo credit: Amelia Armstrong

 

Satellite tagging

Satellite tags, as the name suggests, interact with the satellite network to give positioning information on manta rays.  Unlike acoustic tags, satellite tags do not require a receiver network so can inform on manta ray movements when they leave areas with receiver stations. We use miniPAT satellite tags by Wildlife Computers (http://wildlifecomputers.com/our-tags/minipat/) to track mantas. These tags use light levels and sea surface temperature to estimate the position of the manta underwater. After a set deployment of 3 months, the tags pop off and send this information to the Argos satellite system and then eventually to us. We can receive much more detailed information if we can retrieve the tag, including depth and temperature profiles.  

Project Manta has used satellite tags to track manta rays around Lady Elliot Island in eastern Australia (Jaine et al. 2014). A critical finding of this project was the identification of an important feeding hotspot for manta rays in the Capricorn Eddy. This large patch of circling water results in upwellings of bottom dwelling plankton, and satellite tags showed that mantas frequently visit this region. 

Acoustic tagging
Photo credit: Asia Armstrong

Research directions

We are currently using satellite tags to investigate offshore movements of manta rays in Western Australia (Coral Bay, Ningaloo Reef) and far north Qld (Osprey Reef).