Precision and accuracy of fish length measurements obtained with two visual underwater methods

Type Article
Date 2006
Language English
Author(s) Rochet Marie-Joelle1, Cadiou Jean-Francois2, Trenkel VerenaORCID1
Affiliation(s) 1 : IFREMER, Lab MAERHA, F-44311 Nantes 03, France.
2 : IFREMER, DNIS, SM IM, Ctr Mediterranee, F-83507 La Seyne Sur Mer, France.
Source Fishery Bulletin (0090-0656) (NOAA Governmental fisheries science publications), 2006 , Vol. 104 , N. 1 , P. 1-9
WOS© Times Cited 18
Keyword(s) Auto focus method, Laser method, Error estimation, Measurement methods, Fish lenght
Abstract During the VIITAL cruise in the Bay of Biscay in summer 2002, two devices for measuring the length of swimming fish were tested: 1) a mechanical crown that emitted a pair of parallel laser beams and that was mounted on the main camera and 2) an underwater auto-focus video camera. The precision and accuracy of these devices were compared and the various sources of measurement errors were estimated by repeatedly measuring fixed and mobile objects and live fish. It was found that fish mobility is the main source of error for these devices because they require that the objects to be measured are perpendicular to the field of vision. The best performance was obtained with the laser method where a video-replay of laser spots (projected on fish bodies) carrying real-time size information was used. The auto-focus system performed poorly because of a delay in obtaining focus and because of some technical problems.
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Rochet Marie-Joelle, Cadiou Jean-Francois, Trenkel Verena (2006). Precision and accuracy of fish length measurements obtained with two visual underwater methods. Fishery Bulletin, 104(1), 1-9. Open Access version :