Manta ray (Manta alfredi) visitation to Ningaloo Reef, WA – The importance of residence!

The year round visitation to Ningaloo Marine Park (NMP) of the coastal manta ray (Manta alfredi) has been investigated using the AATAMS acoustic tagging network. A total of 37 individuals were tagged with acoustic ‘pingers’, including 6 with depth tags. Over 10,000 detections were recorded along the length of the array over a three year period. Visitation patterns match photographic sighting data and confirm that manta ray visitation to NMP can be grouped into 3 broad categories, seasonal, roaming and resident. Seasonal aggregations of manta rays at NMP coincide with major reef spawning events which also attract other large planktivores such as the whaleshark. Roaming individuals largely comprise adult males, whilst true residency appears to be the domain of large breeding females. These females show strong fidelity to feeding and cleaning sites, where they interact on occasion with both roaming and seasonal individuals. Their occurrence at numerous small-scale spawning events and zooplankton blooms throughout their potential range indicates the importance of local knowledge. Such on-site knowledge may make resident manta rays key regulators of larval recruitment to the reef system and may play an important role in the reduction of potentially invasive species. The currently un-regulated and growing tourism industry appears to rely heavily on the frequent visitation to key areas of resident manta rays. Any avoidance of these high tourism areas by resident animals could be detrimental to both localized reef health and indeed the lucrative tourism industry of NMP. Acoustic tracking is proving invaluable in our understanding of habitat visitation and manta ray residency within NMP and will assist directly with future management of NMP.