title: Risks and advantages of using surface laser photogrammetry on free-ranging marine organisms: a case study on white sharks Carcharodon carcharias.
abstract: This study employed a non-lethal measurement tool, which combined an existing photo-identification technique with a surface, parallel laser photogrammetry technique, to accurately estimate the size of free-ranging white sharks Carcharodon carcharias. Findings confirmed the hypothesis that surface laser photogrammetry is more accurate than crew-based estimations that utilized a shark cage of known size as a reference tool. Furthermore, field implementation also revealed that the photographer's angle of reference and the shark's body curvature could greatly influence technique accuracy, exposing two limitations. The findings showed minor inconsistencies with previous studies that examined pre-caudal to total length ratios of dead specimens. This study suggests that surface laser photogrammetry can successfully increase length estimation accuracy and illustrates the potential utility of this technique for growth and stock assessments on free-ranging marine organisms, which will lead to an improvement of the adaptive management of the species.
authors.affiliation: Applied Biology, HAS University of Applied Sciences, 's-Hertogenbosch, 5200 MA, The Netherlands.
authors.forename: G
authors.initials: G
authors.lastname: Leurs
authors.affiliation: School of Marine Science and Technology, University of Massachusetts Dartmouth, New Bedford, MA 02740, U.S.A.|O'Seas Conservation Foundation, Bronx, NY 10463, U.S.A.
authors.forename: C P
authors.initials: CP
authors.lastname: O'Connell
authors.affiliation: Evolutionary Genomics Group, Department of Botany and Zoology, Private Bag X1, Stellenbosch University, Stellenbosch 7600, South Africa.
authors.forename: S
authors.initials: S
authors.lastname: Andreotti
authors.affiliation: Shark Diving Unlimited, Kleinbaai, Gansbaai 7220, South Africa.
authors.forename: M
authors.initials: M
authors.lastname: Rutzen
authors.affiliation: Applied Biology, HAS University of Applied Sciences, 's-Hertogenbosch, 5200 MA, The Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: Vonk Noordegraaf
mesh_terms: D000818:Animals; D049628:Body Size; D007834:Lasers; D010780:Photogrammetry / Q000379:methods*; D012754:Sharks / Q000033:anatomy & histology*
keywords: Lamnidae; elasmobranch size; elasmobranchs; endothermic; rete mirabile; shark age