The geographic distribution of reef and oceanic manta rays (Mobula alfredi and Mobula birostris) in Australian coastal waters

Abstract

The known distribution of manta rays in Australian waters is patchy, with records primarily centred around tourism hotspots. We collated 11,614 records of Mobula alfredi from photo‐ID databases (n = 10,715), aerial surveys (n = 378) and online reports (n = 521). The study confirms an uninterrupted coastal distribution from north of 26°S and 31°S on the west and east coasts, respectively. More southerly M. alfredi records relate to warm‐water events with a southernmost extent at 34°S. Coastal sightings of Mobula birostris were rare (n = 32), likely reflecting a preference for offshore waters, but encompass a wider latitudinal extent than M. alfredi of 10–40°S.

Satellite Tagging and Photographic Identification Reveal Connectivity Between Two UNESCO World Heritage Areas for Reef Manta Rays

“…Movements and feeding aggregations of planktivorous elasmobranchs are typically tied to seeking and exploiting better foraging grounds or ephemeral pulses of prey items that are often associated with frontal features (Rohner et al, 2018;Weeks et al, 2015;Anderson et al, 2011;Wilson et al, 2001;Sims et al, 2006). Sighting records from Shark Bay note the presence of multiple manta rays and whale sharks in the same core activity use area identified by our study (Preen et al, 1997;Armstrong et al, 2020), overlapping spatially with areas elevated primary productivity at the northern opening to the bay (Hanson et al, 2005;Nahas et al, 2005). Although M. alfredi likely gains considerable nutrition from deep water plankton (Couturier et al, 2013), the overlap of multiple tag tracks with an oceanographically dynamic but shallow region may be indicative of larger aggregations of M. alfredi at this location.…”

“…Dampier is at the southern end of a coastal movement corridor for many migratory marine species and is in close proximity to increasing volumes of shipping traffic (see Pendoley et al, 2014). Although feeding aggregations of M. alfredi have been previously reported in the region (Armstrong et al, 2020), the likely origin of the animals visiting this location had not been established. Ship strike is a threat to many megafaunal species, including M. alfredi, and given the species' behavioural preference of occupancy of the upper 20 m of the water column (Jaine et al, 2014, Peel, 2019 and the increasing boat traffic in regions adjacent to the Ningaloo WHA (see Bejder et al, 2019), it is perhaps unsurprising that ship strike injuries have come to recent attention.…”

“…The behaviour displayed by each individual when sighted was categorised (as in Germanov et al, 2019), and was informed by ancillary observations reported by tourism operators or trained observers, or through indications of behaviour evident in the photographs. Sightings of Mobula birostris at Ningaloo Reef are relatively infrequent (Armstrong et al, 2020) and as such the species was excluded from this study.…”

“…In Australia, M. alfredi is coastally distributed to ∼30 • S on the east and west coasts, with a continuous northerly distribution between coastlines (Armstrong et al, 2020, Couturier et al, 2012. Although capable of long-distance movements of at least 1100 km (Armstrong et al, 2019), records for M. alfredi suggest they typically traverse shorter distances and display strong site affinity (Clark, 2010;Couturier et al, 2011;Germanov and Marshall, 2014;Germanov et al, 2019;Jaine et al, 2014;Peel, 2019;Venables et al, 2020).…”

Reverse diel vertical movements of oceanic manta rays off the northern coast of Peru and implications for conservation

“…Studies investigating the movement ecology of the oceanic manta ray ( Mobula birostris ) are currently limited in comparison to those of the closely related reef manta ray ( Mobula alfredi ) (Stewart et al., 2016; Stewart et al., 2018). This is likely due to the relatively sparse distribution of oceanic mantas in offshore habitats which can be difficult to access (Armstrong et al., 2020; Kashiwagi et al., 2011). Given that oceanic mantas have extremely conservative life histories, they face threats such as direct and indirect fishing pressure and are listed as ‘Endangered’ on the IUCN Red List of Threatened Species (Croll et al., 2016; Marshall et al., 2020), it is vital that we obtain a greater understanding of their movement ecology in order to implement effective conservation strategies.…”