A hitchhiker guide to manta rays: Patterns of association between Mobula alfredi, M. birostris, their symbionts, and other fishes in the Maldives

Abstract

Despite being among the largest and most charismatic species in the marine environment, considerable gaps remain in our understanding of the behavioural ecology of manta rays (Mobula alfredi, M. birostris). Manta rays are often sighted in association with an array of smaller hitchhiker fish species, which utilise their hosts as a sanctuary for shelter, protection, and the sustenance they provide. Species interactions, rather than the species at the individual level, determine the ecological processes that drive community dynamics, support biodiversity and ecosystem health. Thus, understanding the associations within marine communities is critical to implementing effective conservation and management. However, the underlying patterns between manta rays, their symbionts, and other hitchhiker species remain elusive. Here, we explore the spatial and temporal variation in hitchhiker presence with M. alfredi and M. birostris throughout the Maldives and investigate the factors which may influence association using generalised linear mixed effects models (GLMM). For the first time, associations between M. alfredi and M. birostris with hitchhiker species other than those belonging to the family Echeneidae are described. A variation in the species of hitchhiker associated with M. alfredi and M. birostris was identified, with sharksucker remora (Echeneis naucrates) and giant remora (Remora remora) being the most common, respectively. Spatiotemporal variation in the presence of manta rays was identified as a driver for the occurrence of ephemeral hitchhiker associations. Near-term pregnant female M. alfredi, and M. alfredi at cleaning stations, had the highest likelihood of an association with adult E. naucrates. Juvenile E. naucrates were more likely to be associated with juvenile M. alfredi, and a seasonal trend in E. naucrates host association was identified. Remora were most likely to be present with female M. birostris, and a mean number of 1.5 ± 0.5 R. remora were observed per M. birostris. It is hoped these initial findings will serve as the basis for future work into the complex relationships between manta rays and their hitchhikers.

Demographics and dynamics of the world’s largest known population of oceanic manta rays Mobula birostris in coastal Ecuador

“…The higher apparent survival and higher number of sightings of males that we report here could be indicative of either higher site fidelity to IDLP and Bajo Copé by males, or differing geographic ranges or habitat use in males and females, with our study sites located closer to the activity centre of males than females. In M. alfredi, it is hypothesised that higher sightings of females around cleaning stations may be driven by demographic differences in habitat use (Stevens 2016, Nicholson-Jack et al 2021. Shifts from female to male bias of M. alfredi at cleaning stations have been observed during periods of courtship and mating in the Maldives, raising the possibility that these sites could be used as leks (Stevens 2016).…”

Sublethal Injuries and Physical Abnormalities in Maldives Manta Rays, Mobula alfredi and Mobula birostris

“…Mobula alfredi and M. birostris are commonly sighted in association with smaller hitchhiker species (e.g., sharksucker remora Echeneis naucrates and giant remora Remora remora) (Nicholson-Jack et al, 2021), which utilise their hosts for benefits such as increased food availability and shelter from predation, in exchange for removing parasites from their hosts' bodies (Cressey and Lachner, 1970;Flammang et al, 2020;Solleliet-Ferreira et al, 2020). While remoras are often described as a beneficial symbiont for manta rays (Stevens et al, 2018a), this study is the first to describe injuries, sometimes severe, which can result from close association with these hitchhikers.…”

“…Predator avoidance and thermoregulation may also be functions of shallow coral reef site use (Stevens, 2016). Mobula birostris are less frequently sighted, except during a few months each year (March-April) at Addu and Fuvahmulah, the two southernmost atolls of the archipelago (Stevens, 2016;Maldvian Manta Ray Project [MMRP], 2019a;Nicholson-Jack et al, 2021). These areas are close to deep-water oceanic habitat (Stevens, 2016), where M. birostris are most commonly encountered throughout their range (Kashiwagi et al, 2011;Stewart et al, 2016a).…”

Manta and devil ray species occurrence and distribution in Venezuela, assessed through fishery landings and citizen science data

“…Despite the potential for manta ray‐related eco‐tourism activities to provide sustainable economic benefits to the area, the Venezuelan political and economic situation has hindered the growth of tourism in recent decades (Gutiérrez & Narváez, 2015). Consequently, citizen science data availability for mobulids and other megafauna in Venezuela are few compared to other countries, such as Australia (Armstrong et al ., 2019), the Solomon Islands (Chin et al ., 2020), Maldives (Nicholson‐Jack et al ., 2021; Strike et al ., 2022), Sri Lanka (Fernando & Stewart, 2021) and the Mexican Pacific (Becerril‐García et al ., 2019). Nevertheless, the limited citizen science data the authors were able to source still constitute a base to build knowledge of mobulid species diversity, abundance and distribution in Venezuela.…”

“…Venezuela are few compared to other countries, such as Australia(Armstrong et al, 2019), the Solomon Islands(Chin et al, 2020), Maldives(Nicholson-Jack et al, 2021;Strike et al, 2022), Sri Lanka(Fernando & Stewart, 2021) and the Mexican Pacific(Becerril-García et al, 2019). Nevertheless, the limited citizen science data the authors were able to source still constitute a base to build knowledge of mobulid species diversity, abundance and distribution in Venezuela.The locations identified by Notarbartolo diSciara and Hillyer (1989) in northeastern Venezuela and the locations identified by citizen scientists provide evidence to support Farall on Centinela, Los Roques Archipelago Islands, Chichiriviche de la Costa and Morrocoy National Park as potential manta ray sighting hotspots.…”