The Relative Abundance and Occurrence of Sharks off Ocean Beaches of New South Wales, Australia

Monteforte, Kim I. P.; Butcher, Paul A.; Morris, Stephen; Kelaher, Brendan P.

doi:10.3390/biology11101456

Cited by 4 publications

(1 citation statement)

References 72 publications

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“…Many animals, across a variety of taxa exhibit philopatry [ 68 ], with individuals repeatedly returning to the same stretch of coast for reproductive needs [ 66 , 69 , 70 ], foraging opportunities [ 37 , 71 , 72 , 73 ] or for reasons still largely unknown [ 26 ]. Additionally, ocean currents [ 19 ], water temperature [ 18 , 74 , 75 , 76 , 77 ], rainfall [ 38 , 39 ] and swell height [ 26 , 78 ] are well documented drivers of shark movement patterns and drivers of the behaviour shown here. Similarities among the broad-scale movement patterns of large bull sharks were observed, with large sharks exhibiting latitudinal migrations with increased detection during the austral summer and autumn.…”

Section: Discussionmentioning

confidence: 99%

Bull Shark (Carcharhinus leucas) Occurrence along Beaches of South-Eastern Australia: Understanding Where, When and Why

Smoothey,

Niella,

Brand

et al. 2023

Biology

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Unprovoked shark bites have increased over the last three decades, yet they are still relatively rare. Bull sharks are globally distributed throughout rivers, estuaries, nearshore areas and continental shelf waters, and are capable of making long distance movements between tropical and temperate regions. As this species is implicated in shark bites throughout their range, knowledge of the environmental drivers of bull shark movements are important for better predicting the likelihood of their occurrence at ocean beaches and potentially assist in reducing shark bites. Using the largest dataset of acoustically tagged bull sharks in the world, we examined the spatial ecology of 233 juvenile and large (including sub-adult and adult) bull sharks acoustically tagged and monitored over a 5.5-year period (2017–2023) using an array of real-time acoustic listening stations off 21 beaches along the coast of New South Wales, Australia. Bull sharks were detected more in coastal areas of northern NSW (<32° S) but they travelled southwards during the austral summer and autumn. Juveniles were not detected on shark listening stations until they reached 157 cm and stayed north of 31.98° S (Old Bar). Intra-specific diel patterns of occurrence were observed, with juveniles exhibiting higher nearshore presence between 20:00 and 03:00, whilst the presence of large sharks was greatest from midday through to 04:00. The results of generalised additive models revealed that large sharks were more often found when water temperatures were higher than 20 °C, after >45 mm of rain and when swell heights were between 1.8 and 2.8 m. Understanding the influence that environmental variables have on the occurrence of bull sharks in the coastal areas of NSW will facilitate better education and could drive shark smart behaviour amongst coastal water users.

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Section: Discussionmentioning

confidence: 99%

Bull Shark (Carcharhinus leucas) Occurrence along Beaches of South-Eastern Australia: Understanding Where, When and Why

Smoothey,

Niella,

Brand

et al. 2023

Biology

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Spatial and temporal variation of marine megafauna off coastal beaches of south-eastern Queensland, Australia

Cross,

Mitchell,

Dudgeon

et al. 2024

Mar. Freshw. Res.

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Context Coastal beach environments provide habitats for marine megafauna, including turtles, rays, marine mammals and sharks. However, accessing these variable energy zones has been difficult for researchers by using traditional methods. Aims This study used drone-based aerial surveys to assess spatio-temporal variation of marine megafauna across south-eastern Queensland, Australia. Methods Drones were operated at five south-eastern Queensland beaches. Megafauna sightings and key variables including location, month and turbidity were analysed to assess variation across locations. Key results Overall, 3815 individual megafauna were detected from 3273 flights. There were significant differences in the composition of megafauna assemblages throughout the year and among beaches, with megafaunal sightings in >80% of flights conducted off North Stradbroke Island. Conclusions Strong temporal presence was found that is congruent with other studies examining seasonality. This supports the use of drones to provide ecological data for many hard-to-study megafauna species and help inform long-term sustainable management of coastal ecosystems. Implications Results indicated that environmental conditions can influence the probability of sighting marine megafauna during aerial surveys.

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The Effects of Depth and Altitude on Image-Based Shark Size Measurements Using UAV Surveillance

Rex,

Abbott,

Prezgay

et al. 2024

Drones

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Drones are an ecological tool used increasingly in shark research over the past decade. Due to their high-resolution camera and GPS systems, they have been used to estimate the sizes of animals using drone-based photogrammetry. Previous studies have used drone altitude to measure the target size accuracy of objects at the surface; however, target depth and its interaction with altitude have not been studied. We used DJI Mavic 3 video (3960 × 2160 pixel) and images (5280 × 3960 pixel) to measure an autonomous underwater vehicle of known size traveling at six progressively deeper depths to assess how sizing accuracy from a drone at 10 m to 80 m altitude is affected. Drone altitudes below 40 m and target depths below 2 m led to an underestimation of size of 76%. We provide evidence that accounting for the drone’s altitude and the target depth can significantly increase accuracy to 5% underestimation or less. Methods described in this study can be used to measure free-swimming, submerged shark size with accuracy that rivals hand-measuring methods.

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The Relative Abundance and Occurrence of Sharks off Ocean Beaches of New South Wales, Australia

Cited by 4 publications

References 72 publications

Bull Shark (Carcharhinus leucas) Occurrence along Beaches of South-Eastern Australia: Understanding Where, When and Why

Bull Shark (Carcharhinus leucas) Occurrence along Beaches of South-Eastern Australia: Understanding Where, When and Why

Spatial and temporal variation of marine megafauna off coastal beaches of south-eastern Queensland, Australia

The Effects of Depth and Altitude on Image-Based Shark Size Measurements Using UAV Surveillance

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