Satellite Remote Sensing in Shark and Ray Ecology, Conservation and Management

Williamson, Michael; Tebbs, Emma; Dawson, Terence P.; Jacoby, David

doi:10.3389/fmars.2019.00135

Cited by 30 publications

(26 citation statements)

References 211 publications

(298 reference statements)

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“…As a result, in 2015 the status of M. asterias was upgraded from "Least Concern" to "Near Threatened" (Nieto et al, 2015). This justifies the prioritization of studies on behaviour, habitat use and movement patterns (Williamson et al, 2019). Brevé et al (2016), using a mark-recapture programme, showed indications of seasonal migration F I G U R E 1 Legend on next page.…”

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confidence: 70%

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Sex differentiation in seasonal distribution of the starry smooth‐hound Mustelus asterias

Brevé

Winter²,

Wijmans

et al. 2020

Journal of Fish Biology

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This mark-recapture study of starry smooth-hound Mustelus asterias tagged during the summer months near the Dutch coast demonstrates a large-scale spatial sex differentiation in their circannual migration patterns and small-scale spatial sex differentiation during summer. Overwintering occurs in the North Sea, English Channel and Bay of Biscay, with significantly more males in the Northern North Sea and more females in the Bay of Biscay. During summer, sheltered sea arms off the Dutch coast were almost exclusively used by adult females. In subsequent summers post-release, both sexes were mostly confined to the Southern North Sea, suggesting philopatry.

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confidence: 70%

“…As a result, in 2015 the status of M. asterias was upgraded from “Least Concern” to “Near Threatened” (Nieto et al ., 2015). This justifies the prioritization of studies on behaviour, habitat use and movement patterns (Williamson et al ., 2019). Brevé et al .…”

Section: Figurementioning

confidence: 99%

Sex differentiation in seasonal distribution of the starry smooth‐hound Mustelus asterias

Brevé

Winter²,

Wijmans

et al. 2020

Journal of Fish Biology

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“…Due to time constraints in territory and the area covered by each of our receivers, our analyses currently do not integrate information about the environmental variables at each monitoring station (i.e. node covariates); further research that incorporates high‐resolution satellite remotely sensed environmental data will be important for exploring the drivers of reef shark movements in these remote locations (Williamson, Tebbs, Dawson, & Jacoby, 2019). That said, a recent study exploring the bleaching and recovery of the scleractinian coral reef communities within BIOT during the consecutive, temperature‐driven mortality events of 2015 and 2016 (Head et al., 2019), showed that our predicted ecological hotspots had lower percentage change in coral cover in response to warming events (e.g.…”

Section: Discussionmentioning

confidence: 99%

Shark movement strategies influence poaching risk and can guide enforcement decisions in a large, remote marine protected area

Jacoby

Ferretti

Freeman

et al. 2020

Journal of Applied Ecology

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Large, remote marine protected areas (MPAs) containing both reef and pelagic habitats, have been shown to offer considerable refuge to populations of reef‐associated sharks. Many large MPAs are, however, impacted by illegal fishing activity conducted by unlicensed vessels. While enforcement of these reserves is often expensive, it would likely benefit from the integration of ecological data on the mobile animals they are designed to protect. Consequently, shark populations in some protected areas continue to decline, as they remain a prime target for illegal fishers. To understand shark movements and their vulnerability to illegal fishing, 3 years of acoustic tracking data, from 101 reef‐associated sharks, were analysed as movement networks to explore the predictability of movement patterns and identify key movement corridors within the British Indian Ocean Territory (BIOT) MPA. We examined how space use and connectivity overlap with spatially explicit risk of illegal fishing, through data obtained from the management consultancy enforcing the MPA. Using individual‐based models, the movement networks of two sympatric shark species were efficiently predicted with distance‐decay functions (>95% movements accurately predicted). Model outliers were used to highlight the locations with unexpectedly high movement rates where MPA enforcement patrols might most efficiently mitigate predator removal. Activity space estimates and network metrics illustrate that silvertip sharks were more dynamic, less resident and link larger components of the MPA than grey reef sharks. However, we show that this behaviour potentially enhances their exposure to illegal fishing activity. Synthesis and applications. Marine protected area (MPA) enforcement strategies are often limited by resources. The British Indian Ocean Territory MPA, one of the world's largest ‘no take’ MPAs, has a single patrol vessel to enforce 640,000 km2 of open ocean, atoll and reef ecosystems. We argue that to optimize the patrol vessel search strategy and thus enhance their protective capacity, ecological data on the space use and movements of desirable species, such as large‐bodied reef predators, must be incorporated into management plans. Here, we use electronic tracking data to evaluate how shark movement dynamics influence species mortality trajectories in exploited reef ecosystems. In doing so we discuss how network analyses of such data might be applied for protected area enforcement.

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“…Although food may be a primary driver of temporal changes in movement, factors such as thermoregulation and predator avoidance, and environmental variables such as sea surface temperature, salinity and current, have been found to also drive temporal changes in movement (91,108). Despite recent developments to our understanding of how environmental variables effect elasmobranch movement (108,109), they are still relatively poorly understood, and investigations should be undertaken to further explore their impact on both spatial and temporal aspects of elasmobranch movement in this region.…”

Section: Discussionmentioning

confidence: 99%

Gap analysis of acoustic tracking data reveals spatial and temporal segregation in sympatric reef sharks

Williamson

Tebbs

Dawson

et al. 2020

Preprint

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Background There are now a wide array of field and laboratory techniques available for gaining insight into the movement and behaviour of sharks. Although acoustic telemetry may lack the fine-scale resolution of some satellite technologies, the low cost and longer battery life make it a powerful tool for investigating elasmobranch behaviour. Here, we develop a novel approach to analysing acoustic telemetry data, using detection gaps to infer movement patterns to and from monitored reef habitats, to investigate spatial and temporal segregation between two sympatric shark species in a large remote MPA. Methods A total of 102 grey reef sharks (Carcharhinus amblyrhynchos) and 76 silvertip sharks (Carcharhinus albimarginatus) were fitted with long-term acoustic transmitters and tracked inside a large acoustic array of reef-based receivers in the British Indian Ocean Territory MPA, between 2014 and 2018. From the resulting dataset (768,081 detections), movements between receivers and recursive loops to the same receiver were identified. Using the durations of inter-receiver movements (i.e. detection gaps), individual behaviours were classified into ‘restricted’ or potential wider ‘out of range’ movements. Drivers of these movements were identified using network analysis, GLMMs and multi-model inference starting from an a priori set of explanatory variables. Results In general, silvertip sharks were more likely to undertake ‘out of range’ movements than grey reef sharks. ‘Out of range’ movements were more common at night compared to during the day, and during the wet season compared to the dry season. In addition, the difference in ‘out of range’ movements between the two species increased at night. These results suggest spatial and temporal segregation of movements between the two species. Conclusions We present a novel analysis of detection gaps from acoustic telemetry data to infer differential movement patterns and describe how species organise in space and time. Furthermore, this approach shows that acoustic telemetry gap analysis can be used for comparative studies, or combined, with other research techniques to better understand the functional role of sharks in reef ecosystems, moving towards more informed strategies for the conservation and management of the marine environment.

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Satellite Remote Sensing in Shark and Ray Ecology, Conservation and Management

Cited by 30 publications

References 211 publications

Sex differentiation in seasonal distribution of the starry smooth‐hound Mustelus asterias

Sex differentiation in seasonal distribution of the starry smooth‐hound Mustelus asterias

Shark movement strategies influence poaching risk and can guide enforcement decisions in a large, remote marine protected area

Gap analysis of acoustic tracking data reveals spatial and temporal segregation in sympatric reef sharks

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