Manta and devil rays are filter-feeding elasmobranchs that are found circumglobally in tropical and subtropical waters. Although relatively understudied for most of the Twentieth century, public awareness and scientific research on these species has increased dramatically in recent years. Much of this attention has been in response to targeted fisheries, international trade in mobulid products, and a growing concern over the fate of exploited populations. Despite progress in mobulid research, major knowledge gaps still exist, hindering the development of effective management and conservation strategies. We assembled 30 leaders and emerging experts in the fields of mobulid biology, ecology, and conservation to identify pressing knowledge gaps that must be filled to facilitate improved science-based management of these vulnerable species. We highlight focal research topics in the subject areas of taxonomy and diversity, life history, reproduction and nursery areas, population trends, bycatch and fisheries, spatial dynamics and Stewart et al. Research Priorities for Mobulid Rays movements, foraging and diving, pollution and contaminants, and sub-lethal impacts. Mobulid rays remain a poorly studied group, and therefore our list of important knowledge gaps is extensive. However, we hope that this identification of high priority knowledge gaps will stimulate and focus future mobulid research.

Understanding how individual behavior shapes the structure and ecology of populations is key to species conservation and management. Like many elasmobranchs, manta rays are highly mobile and wide ranging species threatened by anthropogenic impacts. In shallow-water environments these pelagic rays often form groups, and perform several apparently socially-mediated behaviors. Group structures may result from active choices of individual rays to interact, or passive processes. Social behavior is known to affect spatial ecology in other elasmobranchs, but this is the first study providing quantitative evidence for structured social relationships in manta rays. To construct social networks, we collected data from more than 500 groups of reef manta rays over five years, in the Raja Ampat Regency of West Papua. We used generalized affiliation indices to isolate social preferences from non-social associations, the first study on elasmobranchs to use this method. Longer lasting social preferences were detected mostly between female rays. We detected assortment of social relations by phenotype and variation in social strategies, with the overall social network divided into two main communities. Overall network structure was characteristic of a dynamic fission-fusion society, with differentiated relationships linked to strong fidelity to cleaning station sites. Our results suggest that fine-scale conservation measures will be useful in protecting social groups of M. alfredi in their natural habitats, and that a more complete understanding of the social nature of manta rays will help predict population responses to anthropogenic pressures, such as increasing disturbance from dive-tourism.

Localised population declines and increased pressure from fisheries have prompted the promotion of manta ray interaction tourism as a non-consumptive, yet economically attractive, alternative to the unsustainable harvesting of these animals. Unfortunately, however, wildlife tourism activities have the potential to adversely impact focal species. In order to be sustainable, operations must be managed to mitigate negative impacts. A preliminary assessment of reef manta ray, Manta alfredi, behaviour identified short-term behavioural responses during a third of tourism interactions in the Ningaloo Marine Park, Western Australia. Although it remains unknown whether these responses translate to biologically significant impacts on the population as a whole, it is proposed that the precautionary principle be used to guide management intervention in the absence of conclusive evidence of the magnitude of tourism impacts. The principle supports the implementation of precautionary strategies to protect species and their environment from harm, even when the extent of the harm is yet to be confirmed. An increase in the level of industry management is recommended, including the implementation of a licensing system and adherence of all operators to a mandatory code of conduct during manta ray interactions. Considering the well designed and precautionary-driven management program of the Ningaloo whale shark tourism industry operating within the same marine park, a management program with the same underlying principles and objectives is deemed to be an ideal framework to build a comprehensive management plan for the manta ray interaction industry.

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Highly mobile marine megafauna species, while widely distributed and frequently threatened, often aggregate in distinct localized habitats. Implementation of local management initiatives within these hotspots is more achievable than developing effective conservation strategies that encompass their entire distributions. Such measures have the potential for disproportionate population-level benefits but rely on a detailed understanding of spatiotemporal habitat use. To that end, we examined the residency and small-scale habitat use of 51 whale sharks (Rhincodon typus) over 5 years at an aggregation site in Tanzania using passive acoustic telemetry. Whale sharks were highly resident within and across years, with a combined maximum residency index of 0.39. Although fewer sharks were detected from March to September, residency was high throughout the year. Ancillary photographic-identification data showed that individual residency persisted before and after tag attachment. Kernel utilization distributions (KUD) and movement networks both revealed the same spatiotemporal pattern of habitat use, with a small core habitat (50% KUD area for all sharks combined = 12.99 km 2 ) that predictably changed on a seasonal basis. Activity spaces did not differ with time of day, sex, or size of the sharks, indicating a population-level pattern driven by prey availability. The small and predictable core habitat area at this site means that site-based management options to reduce shark injuries and mortality from boat strike and fishing gear entanglement can be spatially targeted for maximum effectiveness and compliance by human users.

Little is known about the extent of genetic connectivity along continuous coastlines in manta rays, or whether site visitation is influenced by relatedness. Such information is pertinent to defining population boundaries and understanding localized dispersal patterns and behaviour. Here, we use 3057 genome-wide single-nucleotide polymorphisms (SNPs) to evaluate population genetic structure and assess the levels of relatedness at aggregation sites of reef manta rays (Mobula alfredi) in southern Mozambique (n = 114). Contrary to indications of limited dispersal along the southern Mozambican coastline inferred from photo-identification and telemetry studies, our results show no evidence of population structure (nonsignificant F ST < 0.001) for M. alfredi along this coast. We also found no evidence that individuals sampled at the same site were more related than expected by chance for males, females or across both sexes, suggesting that kinship may not influence visitation patterns at these sites. We estimated the effective population size (N e ) of this population to be 375 (95% CI = 369-380). Comparison to a distant eastern Indian Ocean site (Western Australia, n = 15) revealed strong genetic differentiation between Mozambique and Western Australia (F ST = 0.377), identifying the Indian Ocean basin as a barrier to dispersal. Our findings show that genetic connectivity in M. alfredi extends for several hundred kilometres along continuous coastlines. We therefore recommend that the population in Mozambique be considered a discrete management unit, and future conservation plans should prioritize integrated strategies along the entire southern coastline.

Manta rays are internationally threatened species and population declines have been reported in various locations worldwide. As iconic megafauna species, they are also major drawcards for wildlife tourism industries. Economic valuation of these industries can provide an incentive for the protection of species and natural habitats through the creation of marine protected areas (MPAs) and the restriction of harvesting or trade. Site-specific estimates are essential, particularly in developing countries, to promote the nonconsumptive use of resources and develop appropriate management strategies. This study represents the first localized estimate of the economic benefits of manta ray tourism in Mozambique. Data from 478 tourist expenditure surveys, 15 stakeholder surveys, and yearly diver numbers provided by coastal tour operators were used to estimate the economic impact of manta ray tourism in the Inhambane Province. Manta ray–focused tours were estimated to be worth US$10.9 million per year in direct revenue to dive operators in the Inhambane Province, with an estimated direct economic impact (including associated tourism expenditures) of US$34.0 million annually. In the absence of manta ray tourism, between $16.1 million and $25.7 million would be lost to the region each year. Tourist and stakeholder survey responses emphasized the importance of manta rays to Mozambican coastal tourism. Both parties highlighted the need for increased protection of marine species and their environment and showed strong support for the implementation of MPAs along the Inhambane coast.

Intraspecific colour polymorphisms have been the focus of numerous studies, yet processes affecting melanism in the marine environment remain poorly understood. Arguably, the most prominent example of melanism in marine species occurs in manta rays ( Mobula birostris and Mobula alfredi ). Here, we use long-term photo identification catalogues to document the frequency variation of melanism across Indo-Pacific manta ray populations and test for evidence of selection by predation acting on colour morph variants. We use mark–recapture modelling to compare survivorship of typical and melanistic colour morphs in three M. alfredi populations and assess the relationship between frequency variation and geographical distance . While there were large differences in melanism frequencies among populations of both species (0–40.70%), apparent survival estimates revealed no difference in survivorship between colour morphs. We found a significant association between phenotypic and geographical distance in M. birostris , but not in M. alfredi . Our results suggest that melanism is not under selection by predation in the tested M. alfredi populations, and that frequency differences across populations of both species are a consequence of neutral genetic processes . As genetic colour polymorphisms are often subjected to complex selection mechanisms, our findings only begin to elucidate the underlying evolutionary processes responsible for the maintenance and frequency variation of melanism in manta ray populations.