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Aim Our aim was to collect sightings data on oceanic manta rays (Mobula birostris) within the Raja Ampat Archipelago to better understand their population dynamics within the region. These data were compared with environmental variables to seek correlates that may explain any variations in observed sightings frequency. Combined, it is hoped this knowledge will be used to aid effective management of this species in the region. Location Raja Ampat Archipelago, West Papua, Indonesia. Methods We collected and catalogued photo‐identification of individuals to create a sightings database. To generate estimates of abundance, survival, sighting probability and recruitment to the population, we used a POPAN mark–recapture model. We considered time‐varying and fixed values for each parameter and possible covariate relationships of the El Niño–Southern Oscillation (ENSO) and sex. Results A total of 588 individuals were identified over six years, of which 72.4% were female, and 28.2% of individuals were resighted. There was an exponential increase in sightings during the 2015–2016 ENSO event despite constant effort; significant correlation was found between sightings and the multivariate ENSO index and with sea surface temperatures but not with chlorophyll‐a. Mark–recapture analysis shows a clear relationship between ENSO and entry probability, and the most parsimonious model estimated a superpopulation size N of 1875 individuals. Main conclusion Oceanic manta ray distributions appear to be impacted by ENSO‐related climate phenomena. Our findings on the relationship of ENSO to manta sightings and distribution indicate that oceanic manta rays are likely sensitive to large‐scale climatic variability. This illustrates the potential impacts of climate change on oceanic manta populations and the need to consider climate impacts in developing management strategies. Continued photo‐ID, tagging and population genetics would greatly enhance knowledge and help develop management strategies that bolster conservation of the species.

Oceanic manta rays Mobula birostris are declining globally due to fisheries. Past work has shown that movements and distributions of oceanic manta ray populations are sensitive to climatic fluctuations such as the El Niño Southern Oscillation. The Revillagigedo National Park (RNP), Mexico, is a well-known aggregation site for oceanic manta rays. However, published baseline data on population structure and dynamics, and the influence of oceanographic variables on the abundance of oceanic manta rays in the region are lacking. We used 2015–2019 photo-identification data to describe baseline demographic characteristics of this population and to evaluate the influence of environmental factors on population dynamics. A significant sex bias was found with a female:male ratio of 1.4:1. Mark-recapture (MR) was used to estimate monthly abundance and provided the first superpopulation size estimate of 1172 (± 90), representing all individuals using the RNP during the survey period. The MR analysis suggests a significant relationship between the multivariate ENSO index and monthly survival probabilities, and chlorophyll-a as a driver of recruitment in surveyed dive sites. These findings provide a baseline to support effective conservation and management plans for this endangered species in the Mexican Pacific.

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.

The feeding behaviour and the swimming pattern of the reef manta (Manta alfredi) are described based on video recordings conducted in Sudan, Red Sea, Indian Ocean, during June 2001. Three circular swimming patterns are described: horizontal circle pattern, inclined circle pattern and double circle pattern, related to feedings on zooplankton distributed in the water column. The observation of circle-like swimming patterns for reef manta rays in shallow waters expands our knowledge about M. alfredi and suggests that the distribution and abundance of zooplankton influence the occurrence and group size of this species in the studied area, as reported from other localities for Manta species.

Understanding the aggregation and habitat use patterns of a species can aid the formulation and improved design of management strategies aiming to conserve vulnerable populations. We used photo-identification techniques and a novel remote underwater camera system to examine the population sizes, patterns of residency and habitat use of oceanic ( Mobula birostris ) and reef ( Mobula alfredi ) manta rays in Seychelles (5.42°S; 53.30°E) between July 2006 and December 2018. Sightings of M. birostris were infrequent ( n  = 5), suggesting that if aggregation areas for this species exist, they occur outside of the boundary of our study. A total of 236 individual M. alfredi were identified across all surveys, 66.5% of which were sighted at D’Arros Island (Amirante Group) and 22.5% at St. François Atoll (Alphonse Group). Males and females were evenly represented within the identified population. M. alfredi visited a cleaning station at D’Arros Island less frequently during dawn and dusk than at midday, likely due to the adoption of a crepuscular foraging strategy. The remote and isolated nature of the Amirante and Alphonse Group aggregation areas, coupled with the lack of a targeted mobulid fishery in Seychelles, suggests that with appropriate regulations and monitoring, the marine protected areas gazetted within these two groups will benefit the conservation of M. alfredi in Seychelles.

The devil-ray family Mobulidae (order Myliobatiformes) comprises wide-ranging, pelagic batoids, but little is known about their basic ecology. We present the first data on the long-distance movement of mobulid devil rays. We attached pop-up archival satellite tags to 13 individuals of the spine-tail devil rayMobula japanica(disk width 199.5 ± 30.0 cm; mean ± SD) off Baja California Sur to examine their habitat movement patterns. Tags remained on the rays for 83 ± 52 d (mean ± SD). Although their primary prey undergo diel migrations from depths >100 m during the day to the surface at night, tagged individuals spent the majority of their time (89.5 ± 3.1% during the day and 96.8 ± 3.5% at night; mean ± SD) near the surface at a depth of ≤50 m in 20 to 30°C water. Thus,M. japanicalikely forages at night and remains near the surface during the day, where warmer water temperatures likely confer a physiological advantage. Most (8 of 13) individuals moved from the tagging location in the southern Gulf of California to the Pacific coast of Baja California Sur, tracking published records of seasonal patterns in euphausiid abundance, similar to other top predators in the region. The depths and geographic regions occupied byM. japanicacoincide with the focus of artisanal and industrial fisheries. This overlap with fisheries, when combined with the delayed maturity and low reproductive rates of devil rays, raises concerns of potentially damaging high bycatch mortality.