García-Baciero, A., C., Robalino-Mejía, C., Peñaherrera-Palma & H., Villalobos (2025). Comparing the performance of two scientific tools for obtaining fish length measurements. Marine Biology. 172: 125. DOI: 10.1007/s00227-025-04682-9.
Alberto García-Baciero 1, Carlos Robalino-Mejía 1, César Peñaherrera-Palma 2 y Héctor Villalobos 1
Precise descriptions of size structure are crucial for the adaptive management of marine fish populations influenced by human activity and environmental factors. Stereo-video systems are powerful tools for monitoring fish populations. Yet, due to the high investment required in software and equipment, stereo-videography can have some financial issues. This study compared the performance of the commercial software EventMeasure from SeaGIS and the open-access R package StereoMorph. We evaluated the effect of distance to the system, rotation movement of the object, and true length on the accuracy and precision of each software. Additionally, we used a diver-operated stereo-video system to obtain in situ measurements of reef fish species. EventMeasure was generally more accurate (error = 0.53%) and precise (CV = 0.35%) than StereoMorph (error = 4.54%; CV = 0.65%). However, the latter showed errors < 5% when measuring objects at distances up to 4 m and close to the plane axis. The precision for in situ measurements for EventMeasure (CV = 15.0%) was similar to that of StereoMorph (Mean CV = 15.8%). We found a high correlation (? = 0.93, p < 0.001) between paired fish length estimation from both software, although StereoMorph was slightly more precise than EventMeasure (Mean CV = 2.07% and Mean CV = 2.11%, respectively). This open-access software provided suitable accuracy and precision results despite some limitations, offering the option to reduce software costs without compromising accuracy for affordability.
Palabras clave: Stereo-videography; fish; Monitoring; Open-access; Measurements; Length estimates
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