Mutualism promotes site selection in a large marine planktivore

Armstrong, Asia O.; Armstrong, Amelia J.; Bennett, Michael B.; Richardson, Anthony J.; Townsend, Kathy A.; Everett, Jason D.; Hays, Graeme C.; Pederson, Hugh; Dudgeon, Christine L.

doi:10.1002/ece3.7464

Cited by 13 publications

(11 citation statements)

References 79 publications

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“…Area-restricted search theory predicts that animals will remain localised in areas where they have a higher probability of encountering prey ( Bailey et al, 2019 ), and this perhaps explains why some M. alfredi individuals remain in Hanifaru Bay when not feeding. This location also has two cleaning stations used by M. alfredi ( Stevens, 2016 ), and it is hypothesised manta rays will frequent cleaning stations in close proximity to foraging opportunities ( Armstrong et al, 2021 ). Manta rays in Palmyra Atoll used area-restricted searching when adjacent to ledges or channels with high plankton concentrations, but their movements were more random at larger spatial scales ( Papastamatiou, De Salles & McCauley, 2012 ).…”

Section: Discussionmentioning

confidence: 99%

“…Area-restricted searching has also been observed in two dolphin species ( Tursiops truncatus and Delphinus delphis ) in areas of high prey availability, and where they have had previous successful foraging experience, suggesting memory plays a role in their movement ecology ( Bailey et al, 2019 ). For M. alfredi , the apparent preference for returning to the same cleaning stations over time ( Armstrong et al, 2021 ), suggests they may form a cognitive map of shallow reef environments, and this is likely the case for known productivity hotspots as well.…”

Section: Discussionmentioning

confidence: 99%

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Reef manta rays forage on tidally driven, high density zooplankton patches in Hanifaru Bay, Maldives

Armstrong

Stevens²,

Townsend

et al. 2021

PeerJ

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Manta rays forage for zooplankton in tropical and subtropical marine environments, which are generally nutrient-poor. Feeding often occurs at predictable locations where these large, mobile cartilaginous fishes congregate to exploit ephemeral productivity hotspots. Investigating the zooplankton dynamics that lead to such feeding aggregations remains a key question for understanding their movement ecology. The aim of this study is to investigate the feeding environment at the largest known aggregation for reef manta rays Mobula alfredi in the world. We sampled zooplankton throughout the tidal cycle, and recorded M. alfredi activity and behaviour, alongside environmental variables at Hanifaru Bay, Maldives. We constructed generalised linear models to investigate possible relationships between zooplankton dynamics, environmental parameters, and how they influenced M. alfredi abundance, behaviour, and foraging strategies. Zooplankton biomass changed rapidly throughout the tidal cycle, and M. alfredi feeding events were significantly related to high zooplankton biomass. Mobula alfredi switched from non-feeding to feeding behaviour at a prey density threshold of 53.7 mg dry mass m−3; more than double the calculated density estimates needed to theoretically meet their metabolic requirements. The highest numbers of M. alfredi observed in Hanifaru Bay corresponded to when they were engaged in feeding behaviour. The community composition of zooplankton was different when M. alfredi was feeding (dominated by copepods and crustaceans) compared to when present but not feeding (more gelatinous species present than in feeding samples). The dominant zooplankton species recorded was Undinula vulgaris. This is a large-bodied calanoid copepod species that blooms in oceanic waters, suggesting offshore influences at the site. Here, we have characterised aspects of the feeding environment for M. alfredi in Hanifaru Bay and identified some of the conditions that may result in large aggregations of this threatened planktivore, and this information can help inform management of this economically important marine protected area.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Reef manta rays forage on tidally driven, high density zooplankton patches in Hanifaru Bay, Maldives

Armstrong

Stevens²,

Townsend

et al. 2021

PeerJ

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“…These include skin lesions, inflammation, necrosis, bacterial and viral infections, and respiratory disease (Caira and Healy, 2004;Garner, 2013;Murie et al, 2020). However, manta rays are known to visit cleaning stations for the removal of dead or infected tissue (to control infections) and parasites by cleaner fish (Foster, 1985;Grutter, 1999;Marshall, 2008;Armstrong et al, 2021b).…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2022

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Manta ray populations worldwide are vulnerable to sublethal injuries resulting from human activities, e.g., entanglement in fishing line and boat strikes, which have the potential to impact an individual’s health, fitness, and behaviour. Sublethal injuries and physical abnormalities also occur naturally from predation events, deformity, parasites, and disease. To determine the type and frequency of anthropogenic and natural originated injury events affecting Mobula alfredi and M. birostris in the Maldives, we examined data from the Manta Trust’s Maldivian Manta Ray Project (MMRP) database, which contains 73,638 photo-identification (photo-ID) sightings of the two manta ray species from 1987 to 2019. The likely origin of each injury or physical abnormality was determined based on visual assessment of the photo-ID images. Multiple injuries to an individual originating from the same event were grouped for analysis. Generalised linear mixed models (GLMM) were used to investigate the relationship between the occurrence of injury events and the explanatory variables sex and maturity status for both species, with the additional variable site function (cleaning, feeding, cruising) investigated for M. alfredi. Spatial and temporal variations in M. alfredi injury events, and their origin and type, were investigated by calculating the percentage of injury events per sighted individual at each Maldivian atoll, and per re-sighted individual in each year from 2005 to 2019. For both species, injury events were predominantly of natural origin, with predatory bites being the most frequent type. The most common anthropogenic injury type was entanglement in fishing line. Injuries to M. alfredi were significantly more likely to be observed on juveniles than adults, males than females, and at cleaning stations as opposed to feeding or cruising sites. Neither sex nor maturity status were significant explanatory variables for the occurrence of injuries to M. birostris. Highest percentages of anthropogenic injuries per sighted M. alfredi were recorded in North Malé, South Malé, Baa, Addu, and Laamu Atolls, where boat traffic, fishing, and tourism activities are concentrated. Overall, this work greatly improves understanding of the sublethal threats faced by manta rays in the Maldives; identifying focus areas where conservation management actions are required to ensure more effective protection of this threatened species group.

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“…These interactions, rather than the species at the individual level, determine the ecological processes that drive community dynamics, support biodiversity and ecosystem health [19]. Thus, species should not be considered in isolation, and understanding the associations within marine communities is critical to implementing effective conservation and management [5,18,20]. Studies that incorporate habitat-specific interactions provide an opportunity to unveil populationwide and long-term patterns into the spatial and behavioural ecology of marine fauna [20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

“…Thus, species should not be considered in isolation, and understanding the associations within marine communities is critical to implementing effective conservation and management [5,18,20]. Studies that incorporate habitat-specific interactions provide an opportunity to unveil populationwide and long-term patterns into the spatial and behavioural ecology of marine fauna [20][21][22][23]. However, our understanding of marine symbionts remains limited due to the logistical challenges associated with studying complex associations in mobile organisms over large spatial scales [21,24,25].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2021

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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.

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Mutualism promotes site selection in a large marine planktivore

Abstract: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cited by 13 publications

References 79 publications

Reef manta rays forage on tidally driven, high density zooplankton patches in Hanifaru Bay, Maldives

Reef manta rays forage on tidally driven, high density zooplankton patches in Hanifaru Bay, Maldives

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

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

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