Our results show that visual length estimates are not impacted by shark size and are a valid measurement tool for many aspects of C. Scientists were most accurate, even though crew observe white sharks more frequently.
#Sharks 3d camera driver
Our findings show that experience measuring animals is the most substantial driver of accurate visual length estimates regardless of the amount of exposure to the species being measured. Observer gender and shark size had no impact on the overall accuracy of visual length estimates, but passengers overestimated sharks less than 3 m and underestimated sharks greater than 3 m.
Observer experience on board cage-diving vessels had the greatest effect on the accuracy of visual length estimates, with scientists being more accurate (mean accuracy ± standard error: 23.0 ± 16.5 cm) than crew (39.9 ± 33.8 cm) and passengers (49.4 ± 38.5 cm). Here, we compared visually estimated total length measurements of white sharks, Carcharodon carcharias, during cage-diving operations with measurements obtained from stereo-video cameras and assessed the accuracy of those estimates in relation to suspected biases (shark size, and observer experience and gender) using generalized linear mixed-models and linear regressions.
However, there has been little effort to quantify the accuracy or validity of this technique despite inaccurate size estimates leading to incorrect population assessments and misinformed management strategies. Visual estimates have been used extensively to determine the length of large organisms that are logistically challenging to measure.
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