A holistic approach to manta ray conservation in the Papuan Bird’s Head Seascape: Resounding success, ongoing challenges

Setyawan, Edy; Erdmann, Mark V.; Gunadharma, Nikka; Gunawan, Tiene; Hasan, Abdi W.; Izuan, Muhamad; Kasmidi, Meidiarti; Lamatenggo, Yusdi; Lewis, Sarah A.; Maulana, Nugraha; Mambrasar, Ronald; Mongdong, Meity; Nebore, Alberth; Putra, Mochamad Iqbal Herwata; Sianipar, Abraham B.; Thebu, Kristian; Tuharea, Syafri; Constantine, Rochelle

doi:10.1016/j.marpol.2021.104953

Cited by 13 publications

(17 citation statements)

References 38 publications

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“…Additional information is now needed to guide management better to regulate the rapidly expanding marine tourism in the park and prevent undue pressure on the manta rays in this critical habitat ( e.g . Division of Boating & Ocean Recreation, 2016 ; Germanov et al, 2019a ; Kasmidi & Gunadharma, 2017 ; Setyawan et al, 2022 ; Venables et al, 2016 ). To combat the rising pressure from tourism, in September 2019, the Komodo NP put limitations on the number of boats and divers/snorkelers allowed in the water simultaneously at KM.…”

Section: Discussionmentioning

confidence: 99%

“…Following a sequence of manta ray conservation milestones ( Setyawan et al, 2022 ), including Indonesian regional shark and manta fishing bans in Raja Ampat, West Papua ( Raja Ampat Local Government, 2012 ) and West Manggarai, Flores and Komodo NP ( West Manggarai Local Government, 2013 ), in 2014, both manta ray species were formally protected throughout the entire exclusive economic zone of Indonesia (an area of over 6 million km 2 ; Dharmadi, Fahmi & Satria, 2015 ; Ministry of Marine Affairs & Fisheries, 2014 ). The nation-wide legislative protection of manta rays was adopted after these species were listed on the aforementioned conservation conventions, but the Indonesian government was also incentivized to protect the valuable manta ray tourism industry in the country, estimated to be worth over US$10.6 million per year ( Mustika, Ichsan & Booth, 2020 ; O’Malley, Lee-Brooks & Medd, 2013 ).…”

Section: Introductionmentioning

confidence: 99%

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Residency, movement patterns, behavior and demographics of reef manta rays in Komodo National Park

Germanov

Pierce

Marshall

et al. 2022

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Background The reef manta ray (Mobula alfredi) is a globally threatened species and an iconic tourist attraction for visitors to Indonesia’s Komodo National Park (NP). In 2013, manta ray fishing was banned in Komodo NP and its surroundings, preceding the nationwide manta ray protection in 2014. Over a decade ago, a previous acoustic telemetry study demonstrated that reef manta rays had high fidelity to sites within the park, while more recent photo-identification data indicated that some individuals move up to 450 km elsewhere. Characterization of manta ray demographics, behavior, and a focused assessment on site use of popular tourism locations within the park is vital to assist the Komodo NP Management Authority formulate appropriate manta ray conservation and management policies. Methods This study uses a long-term library (MantaMatcher.org) of photo-identification data collected by researchers and citizen scientists to investigate manta ray demographics and habitat use within the park at four sites frequented by tour operators: Cauldron, Karang Makassar, Mawan, and Manta Alley. Residency and movements of manta rays were investigated with maximum likelihood analyses and Markov movement models. Results A total of 1,085 individual manta rays were identified from photographs dating from 2013 to 2018. In general, individual manta rays displayed a higher affinity to specific sites than others. The highest re-sighting probabilities came from the remote southern site, Manta Alley. Karang Makassar and Mawan are only ~5 km apart; however, manta rays displayed distinct site affinities. Exchange of individuals between Manta Alley and the two central sites (~35.5 km apart) occurred, particularly seasonally. More manta rays were recorded traveling from the south to the central area than vice versa. Female manta rays were more mobile than males. Similar demographic groups used Karang Makassar, Mawan, and Manta Alley for foraging, cleaning, cruising, or courtship activities. Conversely, a higher proportion of immature manta rays used the northern site, Cauldron, where foraging was commonly observed. Fishing gear-related injuries were noted on 56 individuals (~5%), and predatory injuries were present on 32 individuals (~3%). Tourism within the park increased from 2014 to 2017, with 34% more dive boats per survey at Karang Makassar and Mawan. Discussion The Komodo NP contains several distinct critical habitats for manta rays that encompass all demographics and accommodate seasonal manta ray movements. While the present study has not examined population trends, it does provide foundational data for such work. Continued research into manta ray abundance, long-range movements, and identifying and protecting other critical aggregation areas within the region is integral to securing the species’ recovery. We provide management recommendations to limit undue pressure on manta rays and their critical habitats from tourism.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Residency, movement patterns, behavior and demographics of reef manta rays in Komodo National Park

Germanov

Pierce

Marshall

et al. 2022

PeerJ

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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%

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

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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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“…Nonetheless, there are anecdotal reports of sporadic targeting of manta ray aggregations in the early 2000s by shark fishers in northern Raja Ampat (Varkey et al, 2010). Local fishers also reported that manta rays were frequently observed as bycatch when outsider fishing boats using large drift nets occasionally operated in Raja Ampat in the 1990s and early 2000s (Setyawan et al, 2022a). Importantly, Raja Ampat's manta rays have been protected since 2007, when the Raja Ampat local government and local stakeholders started to implement a series of conservation measures in the region that began with the implementation of a network of MPAs, progressed to the declaration of all of Raja Ampat's regency waters as Southeast Asia's first shark and ray sanctuary in 2012, and culminated with the Indonesian government granting full national-level protection to both species of manta ray in 2014 (Setyawan et al, 2022a).…”

Section: Introductionmentioning

confidence: 99%

“…Similarly, Rohner et al (2013; reported dramatic declines in M. alfredi sightings in southern Mozambique (with a 98% decrease between 2003 and 2016), while numerous authors have noted that the life history characteristics of manta rays (including late maturation and extremely low fecundity) make them highly vulnerable to population decline (Ward-Paige et al, 2013;Dulvy et al, 2014;Croll et al, 2015). While anecdotal evidence and testimonies by local communities and marine tourism operators suggest that Raja Ampat's M. alfredi population has been spared such a fate (Setyawan et al, 2022a), the aim of this paper is to examine manta ray population trends in Raja Ampat in a quantitative manner. Here, we used open population mark-recapture models based on photo-ID sighting data of M. alfredi sourced from citizen science and active surveys by the authors to explicitly examine the potential impacts of manta ray conservation and management efforts in the extensive Raja Ampat MPA network.…”

Section: Introductionmentioning

confidence: 99%

Population estimates of photo-identified individuals using a modified POPAN model reveal that Raja Ampat’s reef manta rays are thriving

et al. 2022

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The 6.7-million-hectare Raja Ampat archipelago is home to Indonesia’s largest reef manta ray (Mobula alfredi) population and a representative network of nine marine protected areas (MPAs). However, the population dynamics of M. alfredi in the region are still largely unknown. Using our photo-identification database, we fitted modified POPAN mark-recapture models with transience and per capita recruitment parameters to estimate key demographic characteristics of M. alfredi from two of Raja Ampat’s largest MPAs: Dampier Strait and South East (SE) Misool. A total of 1,041 unique individuals were photo-identified over an 11-year period (2009–2019) from Dampier Strait (n = 515) and SE Misool (n = 536). In our models, apparent survival probabilities and per capita recruitment rates were strongly linked with El Niño–Southern Oscillation (ENSO) events. Our models also estimated high apparent survival probabilities and significant increases in (sub)population sizes in both MPAs over a decade. In Dampier Strait, the estimated population size increased significantly (p = 0.018) from 226 (95% CI: 161, 283) to 317 (280, 355) individuals. Likewise, the estimated population size in SE Misool increased significantly (p = 0.008) from 210 (137, 308) to 511 (393, 618) individuals. Regardless of variation in the percentage change in population size between years throughout the study, the estimated overall population change shows a compound growth of 3.9% (0.7, 8.6) per annum in Dampier Strait and 10.7% (4.3, 16.1) per annum in SE Misool. Despite the global decline in oceanic sharks and rays due to fishing pressure in the last five decades, our study demonstrates the positive impact of a suite of long-term conservation efforts, coupled with the influence of ENSO events, on increasing M. alfredi abundance in Raja Ampat MPAs. Our study also underscores the importance of long-term monitoring to evaluate the effectiveness of conservation management measures on manta ray populations. Our modification of the standard POPAN model by incorporating per capita recruitment and transience parameters represents an important advance in mark-recapture modelling that should prove useful when examining other manta ray populations and other highly migratory species that are likely to have a substantial percentage of transient individuals.

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A holistic approach to manta ray conservation in the Papuan Bird’s Head Seascape: Resounding success, ongoing challenges

Cited by 13 publications

References 38 publications

Residency, movement patterns, behavior and demographics of reef manta rays in Komodo National Park

Residency, movement patterns, behavior and demographics of reef manta rays in Komodo National Park

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

Population estimates of photo-identified individuals using a modified POPAN model reveal that Raja Ampat’s reef manta rays are thriving

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