Evaluating techniques for determining elasmobranch body size: a review of current methodologies

PeerJ, Journal Year: 2024, Volume and Issue: 12, P. e18646 - e18646

Published: Dec. 23, 2024

There is global awareness that many species of elasmobranchs (sharks and rays) have life history characteristics make them susceptible to overexploitation. The study these animals critical, as it contributes increasing knowledge specimens aids in their conservation. In particular, growth rate, age, fecundity, size at maturity are key parameters for defining management conservation strategies elasmobranchs. Biometric data collection allows be determined considered the evaluation population demography. Over last decades, several methodologies measuring elasmobranch evolved, progressing from traditional capture-based methods sophisticated, non-intrusive photographic techniques. present review aims understand analyse all existing non-invasive techniques currently allow zoometric and, later, highlight advantages limitations each technique, with comments on application fieldwork. To this end, 49 articles were selected, encompassing seven measurement techniques: photogrammetry using distance individual, bar photogrammetry, laser stereo-DOV, stereo-BRUV, stereo-ROV, aerial photogrammetry. Globally, four excellent alternatives involve animal capture or death, they practical, simple use, minimally invasive, potentially highly accurate. Each technique’s requirements related equipment cost, limitations, distinctive features presented here summarized guide researchers what’s available how select most appropriate studies.

Language: Английский

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Computer vision‐assisted photogrammetry and one‐image 3D modeling in marine mammals

Marine Mammal Science, Journal Year: 2023, Volume and Issue: 40(2)

Published: Nov. 2, 2023

Abstract Image processing using traditional photogrammetric methods is a labor‐intensive process. The collection of photogrammetry images during aerial surveys expanding rapidly, creating new challenges to analyze promptly and efficiently, while reducing human error processing. Computer vision‐assisted photogrammetry, field artificial intelligence (AI), can automate image processing, greatly enhancing the efficiency photogrammetry. Here, we present practical efficient program capable automatically extracting fine‐scale East Asian finless porpoises ( Neophocaena asiaeorientalis sunameri ). Our results indicated that computer could achieve same accuracy as comparisons were validated against direct measurements. Three‐dimensional (3D) models morphometrics generated trustworthy body volume estimates. We also explored one image‐based 3D modeling technique, which less accurate, but still useful when only animal available. Although several limitations exist in current program, improvements be made narrow virtual‐reality gap more are available for machine learning training. recommend this analyzing marine mammals possessing similar morphological contour.

Language: Английский

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Using Drones with Thermal Imaging to Estimate Population Counts of European Hare (Lepus europaeus) in Denmark

Drones, Journal Year: 2022, Volume and Issue: 7(1), P. 5 - 5

Published: Dec. 21, 2022

Drones equipped with thermal cameras have recently become readily available, broadening the possibilities for monitoring wildlife. The European hare (Lepus europaeus) is a nocturnal mammal that closely monitored in Denmark due to populations declining since mid-1900s. limitations of current population-assessment methods, such as, spotlight counts and hunting game statistics, could be overcome by relying on drone surveys imaging population counts. aim this study was investigate use DJI Mavic 2 Enterprise Advanced as tool Danish population. Multiple test flights were conducted over agricultural areas spring 2022, testing various flight altitudes, camera settings, recording methods. used suggest method identifying counting hares. applied methodology then evaluated through case survey had hares an area 242 ha. Hares detected at altitudes up 80 m, it possible fly low 40 m without observing direct behaviorial changes. Thermal images taken these also provided enough detail differentiate between species, animal body size proved good species indicator. supported imaging-based identify conduct counts, thus indicating suggested viable alternative traditional

Language: Английский

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Investigating manta ray collective movements via drone surveys

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2022, Volume and Issue: unknown

Published: Aug. 1, 2022

Abstract Detailed observational research on free-ranging species of marine megafauna is required to understand their behavioural ecology, including how groups respond environmental and anthropogenic pressures. New technologies are opening up potential for these in the wild, especially group-based collective behaviours. Reef manta rays ( Mobula alfredi ) socially interactive elasmobranchs that form coastal reef habitats. Collective behaviours likely important fitness, but may be disturbed by humans. Using small, remotely-piloted drones, we performed aerial observations ray Raja Ampat, West Papua. We empirically quantified patterns movement relative spatial positions, alignment, speed leadership positions conspecifics. found unique positioning, alignment leadership, differences between sexes, high levels local attraction, which were suggestive distinct behaviour states. suggest ‘rules interaction’ vary at individual level can shift depending social conditions. Leader-follower has broad importance cohesive M. . further studies should consider utilising models motion capture group-level processes.

Language: Английский

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Reproductive behavior of three mobulid species (Mobula mobular, Mobula thurstoni and Mobula munkiana) in the Southern Gulf of California, Mexico

Research Square (Research Square), Journal Year: 2023, Volume and Issue: unknown

Published: June 16, 2023

Abstract We examined the reproductive behavior (courtship and mating) its seasonality in three mobula species, spinetail, bentfin, munk’s devil rays ( Mobula mobular, M. thurstoni , munkiana ) southwestern Gulf of California, Mexico, using boat surveys (with drones in-water observation) (n = 69 survey days), spotter planes 428 flights) citizen science observations 31). whether (1) grounds existed within area for any these (2) followed seasonal patterns (3) if this was similar among species. observed 221 sessions 2017 2021–2022, mobular 10), 3), 208) dispersed along 312 km eastern Baja California Peninsula between 4 m to 6.3 away from coast. Most events 209) occurred La Ventana Ensenada de Muertos area. Courtship mating with following a pattern occurring March August, peak during May. displayed previously undescribed behavior, “courtship vortex”, where 122 individuals were circling clockwise direction five hours groups joining leaving main vortex formation. This study highlights as critical habitat endangered vulnerable mobulid

Language: Английский

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