Natural history of manta rays in the Bird's Head Seascape, Indonesia, with an analysis of the demography and spatial ecology of Mobula alfredi (Elasmobranchii: Mobulidae)

Setyawan, Edy; Erdmann, Mark V.; Lewis, Sarah A.; Mambrasar, Ronald; Hasan, Abdi W.; Templeton, Sabine; Beale, Calvin S.; Sianipar, Abraham B.; Shidqi, Rafid Arifuddin; Heuschkel, Hendrik; Ambafen, Orgenes; Izuan, Muhamad; Prasetia, Mohammad Fakhri; Azizah, Hidayati; Pada, Defy N.; Muljadi, Andreas; Pilkington-Vincett, Rebecca; Dharmadi,; Cerutti-Pereyra, Florencia

doi:10.5281/zenodo.4396260

Cited by 14 publications

(81 citation statements)

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“…Boat strike injuries were most frequent per sighted M. alfredi in one lagoon (Guraidhoo Falhu) and channel area in South Malé Atoll. This site is a busy highway for boat traffic and a key aggregation site for juvenile M. alfredi, which exhibit extremely high site fidelity (Couturier et al, 2018;Germanov et al, 2019;Setyawan et al, 2020). Therefore, any injuries to these juvenile M. alfredi are likely to have occurred in the close vicinity of this site.…”

Section: Discussionmentioning

confidence: 99%

“…In this study, juvenile M. alfredi were more likely to have injuries than adults, which may be a result of life-stage segregation in habitat-use. Juvenile manta rays in the Maldives (Stevens, 2016), Indonesia (Germanov et al, 2019;Setyawan et al, 2020), Palmyra Atoll (McCauley et al, 2014, southeast Florida, United States (Pate and Marshall, 2020), and the Gulf of Mexico (Stewart et al, 2018a) have been shown to reside in shallow reef habitats for longer periods than adults, and in higher numbers, and exhibit long-term habitat use of these areas. It has been suggested that lagoons serve as important nursery grounds for juvenile manta rays, providing benefits such as reliable food availability, refuge from predators (e.g., large pelagic sharks), or the opportunity for thermoregulation via basking behaviour after deep foraging dives (Heupel et al, 2007;McCauley et al, 2014;Stevens, 2016;Stewart et al, 2018a;Germanov et al, 2019;Pate and Marshall, 2020).…”

Section: Discussionmentioning

confidence: 99%

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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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Section: Discussionmentioning

confidence: 99%

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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“…This study was performed in the Raja Ampat Archipelago, West Papua, Eastern Indonesia (Figure 2). This region covers ~4.5 million ha and is home to large populations of both M. alfredi and oceanic manta rays (M. birostris) [36,37] that have been fully protected in this region since 2012 [38]. The surveys were conducted in five areas of Raja Ampat: Wayag lagoon, Yefnabi Kecil fringing reef, the Fam islands, Hol Gam bay, and the patch reefs east of Arborek island (Dampier Strait) (Figure 2).…”

Section: Study Areamentioning

confidence: 99%

“…The surveys were conducted in five areas of Raja Ampat: Wayag lagoon, Yefnabi Kecil fringing reef, the Fam islands, Hol Gam bay, and the patch reefs east of Arborek island (Dampier Strait) (Figure 2). These five areas are all well protected from significant wave action and frequently host adult and/or juvenile M. alfredi surface feeding or cruising in calm water conditions that are ideal for drone photogrammetry [37,39].…”

Section: Study Areamentioning

confidence: 99%

“…The sex of a manta ray is typically determined in ventral view by divers or snorkelers, with the presence of claspers indicating a male and a cloaca indicating a female [12]. Males are considered mature when their claspers are enlarged and calcified and extend posteriorly beyond the pelvic fins [5], a morphological feature that is readily observed from a dorsal view (Figure 4; [37]). While the cloaca of a female manta ray is not visible in dorsal view, the mating scars on the left-wing, a clear sign of a mature female [12], are clearly visible (Figure 4; [37]).…”

Section: Demographic Parametersmentioning

confidence: 99%

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How Big Is That Manta Ray? A Novel and Non-Invasive Method for Measuring Reef Manta Rays Using Small Drones

Setyawan

Stevenson

Izuan

et al. 2022

Drones

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This study explores the application of small, commercially available drones to determine morphometric the measurements and record key demographic parameters of reef manta rays (Mobula alfredi) in Raja Ampat, Indonesia. DJI Mavic 2 Pro drones were used to obtain videos of surface-feeding M. alfredi with a floating, known-length PVC pipe as a reference scale—thus avoiding the need to utilize altitude readings, which are known to be unreliable in small drones, in our photogrammetry approach. Three dimensions (disc length (DL), disc width (DW), and cranial width (CW)) from 86 different individuals were measured. A hierarchical multivariate model was used to estimate the true measurements of these three dimensions and their population-level multivariate distributions. The estimated true measurements of these dimensions were highly accurate and precise, with the measurement of CW more accurate than that of DL and, especially, of DW. Each pairing of these dimensions exhibited strong linear relationships, with estimated correlation coefficients ranging from 0.98–0.99. Given these, our model allows us to accurately calculate DW (as the standard measure of body size for mobulid rays) using the more accurate CW and DL measurements. We estimate that the smallest mature M. alfredi of each sex we measured were 274.8 cm (males, n = 30) and 323.5 cm DW (females, n = 8). We conclude that small drones are useful for providing an accurate “snapshot” of the size distribution of surface-feeding M. alfredi aggregations and for determining the sex and maturity of larger individuals, all with minimal impact on this vulnerable species.

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Reproductive behavior, seasonality, and distribution of three devil ray species (Mobula mobular, M. thurstoni, and M. munkiana) in the Southern Gulf of California, Mexico

Palacios,

Trejo-Ramírez,

Velázquez-Hernández

et al. 2023

Mar Biol

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We examined the reproductive behavior (courtship and mating), seasonality and its distribution in three Mobula species, spinetail, bentfin, and Munk’s devil rays (M. mobular, M. thurstoni, and M. munkiana) in the southwestern Gulf of California, Mexico, using boat surveys (with drone and in-water observations) (n = 69 survey days), spotter planes (n = 428 flights), and citizen science observations (n = 31). We examined whether (1) reproductive grounds existed within the area for any of these species, (2) whether reproductive behavior followed seasonal patterns, and (3) if this behavior was similar among all mobula rays. We observed reproductive behavior in 221 events in 2017 and 2021–2022, for M. mobular (n = 10), M. thurstoni (n = 3), and M. munkiana (n = 208) dispersed along 312 km of the eastern Baja California Peninsula between 4 m and 6.3 km away from the coast. Most events (n = 209) occurred in the La Ventana and Ensenada de Muertos areas. Courtship was observed for M. mobular and M. thurstoni and a copulation attempt for M. munkiana, with reproductive behavior following a seasonal pattern occurring from March to August, with a peak during May (81.9% of the events). Mobula munkiana displayed previously undescribed behaviors, such as the “piggyback leaps” as a pre-copulatory position and the “courtship vortex”, where 122 individuals were observed circling in a clockwise direction for 5 h with courtship groups joining and leaving the main vortex formation. This study highlights the areas of La Ventana and Ensenada de Muertos as critical habitats for reproductive behavior of two endangered and one vulnerable devil ray species.

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Natural history of manta rays in the Bird's Head Seascape, Indonesia, with an analysis of the demography and spatial ecology of Mobula alfredi (Elasmobranchii: Mobulidae)

Cited by 14 publications

References 0 publications

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

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

How Big Is That Manta Ray? A Novel and Non-Invasive Method for Measuring Reef Manta Rays Using Small Drones

Reproductive behavior, seasonality, and distribution of three devil ray species (Mobula mobular, M. thurstoni, and M. munkiana) in the Southern Gulf of California, Mexico

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