Reliability of marine faunal detections in drone-based monitoring

Colefax, Andrew P.; Butcher, Paul A.; Pagendam, Dan; Kelaher, Brendan P.

doi:10.1016/j.ocecoaman.2019.03.008

Cited by 73 publications

(100 citation statements)

References 53 publications

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“…The present study has quantified the diverse range of coastal conditions under which drones can operate, demonstrating their utility for detecting objects in the water (in this case shark analogues), particularly in conditions of reasonable water visibility and depth. Depending on the environmental conditions, drones can potentially be used to spot sharks or other marine fauna along coastal beaches, and could supplement existing aerial survey methods (Colefax et al 2019). Furthermore, drones would provide a cheaper and more versatile platform than manned aircraft for beach authorities and various user groups for localised coastal areas (Colefax et al 2018).…”

Section: Discussionmentioning

confidence: 99%

“…Similarly, rainy conditions would likely impair faunal sightability even if water-resistant drones were used. Precipitation is therefore potentially the main limitation on drone-based shark surveillance, because it can either force surveillance operations to cease or impede faunal sightings (Colefax et al 2019).…”

Section: Discussionmentioning

confidence: 99%

“…One option to improve the efficacy of aerial shark detection is to use drones, also known as remotely piloted aircraft systems (RPAS) or unmanned aerial vehicles (UAV), which are available in a variety of fixed-wing and multi-rotor configurations (Colefax et al 2018). Drones increasingly present an alternative to manned aircraft for a variety of wildlife survey and detection tasks (Kudo et al 2012;Martin et al 2012;Linchant et al 2015;Evans et al 2015;Kiszka et al 2016;Colefax et al 2019;Kelaher et al 2019). In the context of shark patrols, drones offer several potential advantages over manned aircraft because they can operate at individual beaches, and fly constantly at lower airspeeds and altitudes than are physically or legally possible for manned aircraft (Kudo et al 2012;Robbins et al 2014, but see Linchant et al (2015) for possible exceptions).…”

Section: Introductionmentioning

confidence: 99%

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Beach safety: can drones provide a platform for sighting sharks?

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ContextA series of unprovoked shark attacks on New South Wales (Australia) beaches between 2013 and 2015 triggered an investigation of new and emerging technologies for protecting bathers. Traditionally, bather protection has included several methods for shark capture, detection and/or deterrence but has often relied on environmentally damaging techniques. Heightened environmental awareness, including the important role of sharks in the marine ecosystem, demands new techniques for protection from shark attack. Recent advances in drone-related technologies have enabled the possibility of real-time shark detection and alerting. AimTo determine the reliability of drones to detect shark analogues in the water across a range of environmental conditions experienced on New South Wales beaches. MethodsA standard multirotor drone (DJI Inspire 1) was used to detect shark analogues as a proxy during flights at 0900, 1200 and 1500 hours over a 3-week period. The 27 flights encompassed a range of environmental conditions, including wind speed (2–30.0kmh−1), turbidity (0.4–6.4m), cloud cover (0–100%), glare (0–100%), seas (0.4–1.4m), swells (1.4–2.5m) and sea state (Beaufort Scale 1–5 Bf). Key resultsDetection rates of the shark analogues over the 27 flights were significantly higher for the independent observer conducting post-flight video analysis (50%) than for the drone pilot (38%) (Wald P=0.04). Water depth and turbidity significantly impaired detection of analogues (Wald P=0.04). Specifically, at a set depth of 2m below the water surface, very few analogues were seen by the observer or pilot when water turbidity reduced visibility to less than 1.5m. Similarly, when water visibility was greater than 1.5m, the detection rate was negatively related to water depth. Conclusions The present study demonstrates that drones can fly under most environmental conditions and would be a cost-effective bather protection tool for a range of user groups. ImplicationsThe most effective use of drones would occur during light winds and in shallow clear water. Although poor water visibility may restrict detection, sharks spend large amounts of time near the surface, therefore providing a practical tool for detection in most conditions.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Beach safety: can drones provide a platform for sighting sharks?

et al. 2019

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“…With recent technology advances, unmanned aerial vehicles (hereafter called drones; Chapman, ) are being increasingly used for marine wildlife research (Chabot, ; Colefax et al ., ; Kelaher et al ., ; Rieucau et al ., ). Drone surveys are an effective method for quantifying marine megafauna and are being increasingly used to sample large fishes, including sharks, rays, turtles and gamefish (Colefax et al ., ; Kelaher et al ., ). Compared with catch‐based research methods, drones have limited effect on elasmobranchs and can provide similar results to visual census (Raoult & Gaston, ).…”

Section: Introductionmentioning

confidence: 99%

Variation in cownose ray Rhinoptera neglecta abundance and group size on the central east coast of Australia

Tagliafico

Butcher

Colefax

et al. 2019

Journal of Fish Biology

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Here, we provide baseline information about the relative abundance and group size of the Australian cownose ray Rhinoptera neglecta on the central east coast of Australia. Using drone monitoring over 2 years, we completed 293 transects, each 2 km in length, at four locations distributed along c.100 km of coast. In total, 5979 R. neglecta were observed with overall relative abundance (±SE) of, 20.4 (±3.3) individuals per transect. The numbers of R. neglecta varied among locations, with the highest density found off the beach adjacent to the river mouth at Evans Head. The number of rays observed also decreased with increasing wind speed. While some of this relationship was probably associated with visibility, R. neglecta may also move offshore during strong winds. We found no evidence that R. neglecta was under significant threat. Additionally, our costeffective surveys demonstrate the utility of aerial drones in fisheries conservation biology.

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“…Since most fishing traps lay on the bottom, estuarine stretches with deeper bank gradients would have a higher propensity for missing traps, decreasing unmarked trap detectability (would still be able to detect the floats). Thus, the efficacy of a drone utilising an RGB camera would be largely governed by water clarity in relation to the depth in the area of interest (Colefax et al., ).…”

Section: Discussionmentioning

confidence: 99%

Drones detect illegal and derelict crab traps in a shallow water estuary

Bloom

Butcher

Colefax

et al. 2019

Fisheries Management Eco

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The issues surrounding illegal, unregulated and unreported fishing, and that of abandoned, lost and discarded fishing gears, leading to ghost fishing, are intensifying. Estuarine crab trapping is likely subject to high levels of illegal and potential ghost fishing, because it also has good economic incentives regarding potential catch, low gear acquisition costs and accessible fishing grounds. To improve the efficiency and effectiveness of fisheries monitoring, control and surveillance operations, the efficacy of small consumer‐grade drones for sighting traps in an estuary in NSW, Australia, was tested. Twelve sets of two flights were undertaken at 20 and 30 m altitude over a 600‐m stretch of estuary for 5 days to quantify the detectability of submerged mesh traps of three different mesh colours. The drone was able to detect the majority of traps efficiently, with depth in relation to water clarity being the main factor affecting detection. In shallow water, detection rates were high for all mesh colours, but in the slightly deeper placements, orange traps were more readily detected. This study demonstrates that drones could be an efficient and reliable tool for rapidly assessing areas for illegal and derelict traps and can be supplemented into land or vessel‐based fisheries operations.

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Reliability of marine faunal detections in drone-based monitoring

Cited by 73 publications

References 53 publications

Beach safety: can drones provide a platform for sighting sharks?

Beach safety: can drones provide a platform for sighting sharks?

Variation in cownose ray Rhinoptera neglecta abundance and group size on the central east coast of Australia

Drones detect illegal and derelict crab traps in a shallow water estuary

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