Contrasting Habitat Use and Population Dynamics of Reef Manta Rays Within the Nusa Penida Marine Protected Area, Indonesia

Manta rays (Mobula spp.) are highly valued in nature-based tourism globally. In Indonesia, although manta rays are protected, critical information is lacking on their habitat use, population dynamics and movements. We investigate the population structure and residency patterns of reef manta rays (Mobula alfredi) in the Nusa Penida Marine Protected Area (MPA). From photo-identification data logged by citizen scientists and trained observers (mantamatcher.org), we identified 624 reef manta rays from 5,913 sightings (January 2012–April 2018) based on their unique ventral coloration patterns. Year-round records were collected from two shallow (<20 m) reefs – Manta Bay (MB; n = 3,029 sightings) and Manta Point (MP; n = 3,058) – that are used frequently by tourism operators. Maximum likelihood techniques and a Markov movement analysis were used to model residency patterns and movement between these sites within the MPA. Manta rays at MB were predominantly male (64%, n = 261 individuals), with immature males (14%, n = 59) being sighted most frequently (39%, n = 1,170). In contrast, few immature individuals were sighted at MP (6%, n = 28), and they were sighted on few occasions (2%, n = 45), while mature female manta rays comprised 26% (n = 127) of the MP community and were the most frequently sighted (48%, n = 1,413). Lagged identification rates indicated high site fidelity at each location. However, 44% (n = 278) of individuals moved between the two sites and cumulative discovery curves showed a continued recruitment of individuals over the 6 years of the study. In addition, the behaviors displayed by the manta rays differed markedly between the two sites: MB appears to be a foraging ground, especially for juveniles, and potentially a nursery, while MP is used mainly for cleaning and courtship, indicating a social and reproductive site. Reproductive behavior coincided with the peak annual sightings in May. To prevent disturbance to this threatened species by tourism, regulations for the number of boats and interactions, especially during key reproductive times should be considered. Further, strict fishing regulation in the area is recommended as fishing gear entanglement was identified as a threat to this population

Interactions between marine megafauna and plastic pollution in Southeast Asia

Southeast (SE) Asia is a highly biodiverse region, yet it is also estimated to cumulatively contribute a third of the total global marine plastic pollution. This threat is known to have adverse impacts on marine megafauna, however, understanding of its impacts has recently been highlighted as a priority for research in the region. To address this knowledge gap, a structured literature review was conducted for species of cartilaginous fishes, marine mammals, marine reptiles, and seabirds present in SE Asia, collating cases on a global scale to allow for comparison, coupled with a regional expert elicitation to gather additional published and grey literature cases which would have been omitted during the structured literature review. Of the 380 marine megafauna species present in SE Asia, but also studied elsewhere, we found that 9.1 % and 4.5 % of all publications documenting plastic entanglement (n = 55) and ingestion (n = 291) were conducted in SE Asian countries. At the species level, published cases of entanglement from SE Asian countries were available for 10 % or less of species within each taxonomic group. Additionally, published ingestion cases were available primarily for marine mammals and were lacking entirely for seabirds in the region. The regional expert elicitation led to entanglement and ingestion cases from SE Asian countries being documented in 10 and 15 additional species respectively, highlighting the utility of a broader approach to data synthesis. While the scale of the plastic pollution in SE Asia is of particular concern for marine ecosystems, knowledge of its interactions and impacts on marine megafauna lags behind other areas of the world, even after the inclusion of a regional expert elicitation. Additional funding to help collate baseline data are critically needed to inform policy and solutions towards limiting the interactions of marine megafauna and plastic pollution in SE Asia

Research Priorities to Support Effective Manta and Devil Ray Conservation

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 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

The survey effort in Nusa Penida, West Manggarai & Komodo, and Raja Ampat regions including sighting records and number of individuals identified.

<p>The survey effort in Nusa Penida, West Manggarai & Komodo, and Raja Ampat regions including sighting records and number of individuals identified.</p

Running the Gauntlet: Regional Movement Patterns of <i>Manta alfredi</i> through a Complex of Parks and Fisheries

<div><p>Manta rays (Genus <i>Manta</i>) are economically important for fisheries and tourism in Indonesia. These species have been listed by the International Union for the Conservation of Nature Red List as Vulnerable to extinction; therefore, human exploitation of manta rays must be regulated. A better understanding of the habitat use and movement patterns of manta rays in Indonesia is needed in order to employ effective conservation measures. To gain better insight into the movements of <i>Manta alfredi</i> we used ‘Manta Matcher’, an online database with an integrated automated matching algorithm, to compare photographs from 2,604 encounters of <i>M. alfredi</i> collected by recreational divers and dive operators throughout Indonesia over a nine-year period. This photographic comparison revealed that manta rays migrated between regional sanctuaries such as Nusa Penida, the Gili Islands, and the Komodo National Park (up to 450 km straight-line distance). The areas between these sanctuaries are heavily fished and trafficked by ships, and when manta rays travel through these regions they risk being fished and injured by ship strikes. These long-range manta ray movements suggest connectivity between <i>M. alfredi</i> populations in neighboring islands and raise concerns about the future management of regional populations. It is recommended that a national conservation strategy be developed to protect the remaining populations in the country.</p></div

The locations of <i>M. alfredi</i> encounters in Indonesia submitted to Manta Matcher.

<p>Sites are numbered as follows: 1) Pulau Weh 2) Palau Sangalaki 3) Nusa Penida 4) Gili Islands 5) West Manggarai & Komodo National Park 6) Raja Ampat. (A) Connectivity area and commercial fisheries area (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110071#pone-0110071-g002" target="_blank">Figure 2</a> for enlargement). (B) Region surveyed in Raja Ampat (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110071#pone-0110071-g003" target="_blank">Figure 3</a> for enlargement).</p

A map of the Raja Ampat region to indicate the location of different monitoring sites.

<p>Sites are numbered as follows: 1) Manta Sandy 2) Jetty Arborek 3) Blue Magic 4) Manta Ridge 5) Manta Heaven 6) Dayang.</p

The sighting records of individual rays migrating between Nusa Penida and Gili Islands or West Manggarai & Komodo regions.

<p>Arrows highlight direction of movements.</p>⇒<p>west to east movements;</p>⇐<p>east to west movements.</p><p>The sighting records of individual rays migrating between Nusa Penida and Gili Islands or West Manggarai & Komodo regions.</p

The connectivity area encompassing Nusa Penida, West Manggarai & Komodo regions and the nearby commercial manta ray landing ports.

<p>Regions and fishing ports are numbered as follows: 1) Nusa Penida 2) Gili Islands 3) Tunjung Luar fishing port 4) Komodo National Park 5) Lamakera fishing port. (A) Manta ray monitoring sites in Nusa Penida and Lombok and nearby Tujung Luar fishing port: 1.1) Small Manta Bay 1.2) Big Manta Bay 1.3) Manta Point 2) Gili Islands 3) Tanjung Luar fishing port. (B) Manta ray monitoring sites in West Mangarrai and Komodo National Park: 4.1) Manta Alley 4.2) German Flag 4.3) Karang Makassar/Manta Point 4.4) Mawan 4.5) The Cauldron 4.6) Tatawa Besar 4.7) Sabolon Kecil.</p

The ‘Manta Matcher’ matching algorithm screen grabs for INNLP0229A showing the top three matched images.

<p>Ranked hit 1 (re-sighting in WM & K) is a true match for the query image of ray INNLP0229A (initial sighting in NP).</p