Andrialovanirina N. auteur aut IRD Ponton Dominique auteur aut IRD Behivoke F. auteur aut IRD Mahafina J. auteur aut IRD Léopold Marc auteur aut IRD text journalArticle eng text/pdf born digital access Measuring fish length is useful for exploring size structure of catches and fishing effects on marine resources. However manually measuring large numbers of individuals requires time-consuming manipulations, which are hardly operational in the context of tropical small-scale fisheries. To overcome this limitation, we developed a method to automatically measure total fish length using digital images and an analytical procedure using the ImageJ software. For testing this procedure, a total of 180 fishes (3 to 50 cm TL) from 19 families, presenting two color patterns and two caudal fin types, were obtained from small-scale fishers in southwestern Madagascar in 2018. We took standardized images of the fishes using a locally made, cost-effective camera-equipped device. The accuracy of fish size estimates and the time taken for measurements were compared across the ImageJ automatic procedure, manual measurements made on-screen using ImageJ, and measurements using an ichthyometer, the latter providing the reference fish length. The ImageJ automatic measurement procedure reached 98.4% accuracy while the measurement time was reduced by 57% and 40% compared to the measures using an ichthyometer and ImageJ on-screen tools, respectively. We conclude that the automatic measurement procedure provides very effective results for fish < 50 cm TL. This method is relevant for governmental, non-governmental, and research organizations that investigate size-related fishing and management impacts on fish community structure and dynamics. specialized automatic fish measurement catch size structure image analysis reef fish MADAGASCAR 040 122 223 art. 105425 [8 p.] 2020 0165-7836 https://www.documentation.ird.fr/hor/fdi:010077864 10.1016/j.fishres.2019.105425 0165-7836 [F B010077864] https://www.documentation.ird.fr/hor/fdi:010077864 https://www.documentation.ird.fr/intranet/publi/2020/02/010077864.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2020-03-11 2025-11-18 fdi:010077864 fre