Movement patterns of juvenile porcupine rays Urogymnus asperrimus at a remote atoll: a potential nursery ground within a proposed marine protected area

Elston, Chantel; Cowley, Paul D.; Brandis, Rainer G. von

doi:10.1007/s10641-019-00927-x

Cited by 4 publications

(5 citation statements)

References 47 publications

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“…Specifically, the interplay between tide and temperature, and how these changed across seasonal and diel scales, significantly effected the way that stingrays used the dominant habitats associated with the St. Joseph Atoll. Previous work found that juvenile stingrays in this atoll preferentially utilized the shallow sand flat habitat, but did at times occur in the deeper lagoon (Elston et al, 2019(Elston et al, , 2020. The present study suggests that movements between these receivers).…”

Section: Discussionsupporting

confidence: 59%

“…Most individuals (87%) were considered juveniles at the time of tagging. Residency to the atoll was found to be variable between individuals, but overall quite high, and periods of no detections (which could be related to individuals being present in the atoll but not detected, or having left the atoll) were mostly on the scale of days, but could range up to a few months of no detections (Elston et al, 2019).…”

Section: Resultsmentioning

confidence: 95%

“…In the present study, the probability of daily detection was significantly negatively correlated with wind speeds and this trend could be influenced by receiver detection efficiency. Wind speed is known to reduce detection efficiency of receivers, both in this and other receiver arrays (Heupel et al, 2006;Elston et al, 2019). The SE-monsoon season is characterized by persistent strong winds and detections in this season were restricted when compared to the detections in the NW-monsoon season.…”

Section: Discussionmentioning

confidence: 92%

“…Receiver installation was completed in November 2014 and only detection data recorded subsequent to this date were included in the analyses. A month long range test was conducted on the flats, given environmental factors may effect detection probability the most in this shallow habitat, and the probability of detection was found to significantly vary with wind speed but not with tidal cycles or temperature (Elston et al, 2019).…”

Section: Acoustic Telemetrymentioning

confidence: 99%

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Stingray Habitat Use Is Dynamically Influenced by Temperature and Tides

et al. 2022

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Abiotic factors often have a large influence on the habitat use of animals in shallow marine environments. Specifically, tides may alter the physical and biological characteristics of an ecosystem while changes in temperature can cause ectothermic species to behaviorally thermoregulate. Understanding the contextual and relative influences of these abiotic factors is important in prioritizing management plans, particularly for vulnerable faunal groups like stingrays. Passive acoustic telemetry was used to track the movements of 60 stingrays at a remote and environmentally heterogeneous atoll in Seychelles. This was to determine if habitat use varied over daily, diel and tidal cycles and to investigate the environmental drivers behind these potential temporal patterns. Individuals were detected in the atoll year-round, but the extent of their movement and use of multiple habitats increased in the warmer NW-monsoon season. Habitat use varied over the diel cycle, but was inconsistent between individuals. Temperature was also found to influence stingray movements, with individuals preferring the deeper and more thermally stable lagoon habitat when extreme (hot or cold) temperature events were observed on the flats. Habitat use also varied over the tidal cycle with stingrays spending a higher proportion of time in the lagoon during the lowest tides, when movement on the flats were constrained due to shallow waters. The interplay of tides and temperature, and how these varied across diel and daily scales, dynamically influenced stingray habitat use consistently between three species in an offshore atoll.

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Section: Discussionsupporting

confidence: 59%

Section: Resultsmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 92%

Section: Acoustic Telemetrymentioning

confidence: 99%

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Stingray Habitat Use Is Dynamically Influenced by Temperature and Tides

et al. 2022

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“…The fish were captured only on the reef flats because acoustic telemetry revealed that: U . asperrimus spend most of their time in this habitat, rarely moving into the deep lagoon (Elston, ); visual observations confirmed regular feeding in this habitat; hand capture in the deeper (3–7 m) and turbid inner lagoon of the atoll was not possible. Capture effort was relatively evenly dispersed over the reef flats and was not restricted to any specific area of the flats.…”

Section: Methodsmentioning

confidence: 96%

Dietary composition and prey selectivity of juvenile porcupine raysUrogymnus asperrimus

Elston

Brandis

Cowley

2017

Journal of Fish Biology

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Fifty-five juvenile porcupine ray Urogymnus asperrimus were collected in the isolated St Joseph Atoll, Seychelles. Stomach contents were sampled using non-lethal gastric lavage to determine the dietary composition, degree of prey selectivity and whether sex or size affected their diet. Sediment samples were collected to quantify prey availability so that prey selectivity could be estimated. Two phyla (Sipuncula and Nemertea) and 11 polychaete and crustacean families were recorded in stomach contents. Juvenile U. asperrimus appeared to specialize on one polychaete family, Capitellidae, which was the most important prey item (index of importance = 35%). This polychaete family was also most abundant in the sediment samples and U. asperrimus are thus considered opportunistic predators. There was evidence of a size-related shift in the crustacean families consumed by juvenile U. asperrimus. Data collected at this remote location provides important baseline ecological information that may prove useful in developing conservation strategies for this ecologically important species.

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Residency and habitat use patterns by sympatric stingrays at a remote atoll in the Western Indian Ocean

Elston

Cowley

Brandis

et al. 2021

Mar. Ecol. Prog. Ser.

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Information on the spatial ecology of batoids is lacking despite the need for this information for effective management and conservation of this vulnerable faunal group. We used acoustic telemetry to monitor the presence of dasyatids (Pastinachus ater, Urogymnus granulatus, and U. asperrimus) from March 2014 to November 2017 within and around the isolated St. Joseph Atoll, Seychelles. Results highlighted residency (median residency index = 0.75 and 0.57 for P. ater and U. granulatus) over periods of months to years for both juveniles and adults. Individuals displayed highly restricted movements; most detections occurred within 1 km of tagging locations, and movement networks were small and fragmented. However, juveniles increased their range of movements with size before dispersing to various locations on the Amirantes Bank. Within the atoll, resident adults and juveniles segregated ontogenetically by habitat; adults were more reliant on the deeper lagoon, while juveniles were largely restricted to the shallow sand flats, likely in an effort to avoid predators. Conversely, no inter-specific space partitioning was identified. This study provides preliminary evidence that this atoll is a dasyatid nursery; however, comparative research at other atolls is required to understand the role that atolls may play as batoid nurseries. This study was performed in the South West Indian Ocean, an understudied fisheries conservation hotspot where biodiversity is high but management effectiveness is low. The identification of a dasyatid refuge in this region highlights that the current marine protected area designation will likely provide conservation benefits for the dasyatid populations across the entire Amirantes Bank.

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Movement patterns of juvenile porcupine rays Urogymnus asperrimus at a remote atoll: a potential nursery ground within a proposed marine protected area

Cited by 4 publications

References 47 publications

Stingray Habitat Use Is Dynamically Influenced by Temperature and Tides

Stingray Habitat Use Is Dynamically Influenced by Temperature and Tides

Dietary composition and prey selectivity of juvenile porcupine raysUrogymnus asperrimus

Residency and habitat use patterns by sympatric stingrays at a remote atoll in the Western Indian Ocean

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