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Article

Estimating Whale Shark, Rhincodon typus, Length Using Multi-Stereo-Image Measurement

1
Department of Fisheries, Graduate School of Agriculture, Kindai University, 3327-204 Nakamachi, Nara 631-8505, Nara, Japan
2
Department of Natural Environmental Studies, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwano-ha, Kashiwa 277-8564, Chiba, Japan
3
Io World Kagoshima City Aquarium, 3-1 Honkoushinmachi, Kagoshima 892-0814, Kagoshima, Japan
4
Okinawa Churaumi Aquarium, 424 Ishikawa, Motobu 905-0206, Okinawa, Japan
5
Department of Fisheries, Faculty of Agriculture, Kindai University, 3327-204 Nakamachi, Nara 631-8505, Nara, Japan
*
Author to whom correspondence should be addressed.
Fishes 2025, 10(10), 513; https://doi.org/10.3390/fishes10100513
Submission received: 29 August 2025 / Revised: 2 October 2025 / Accepted: 3 October 2025 / Published: 10 October 2025

Abstract

The whale shark Rhincodon typus is the largest known extant omnivorous fish species, reaching up to 17 m in length. Because of its slow growth and late maturity, R. typus is particularly vulnerable to human activities and is listed as endangered on the IUCN Red List. Understanding its biological characteristics, such as growth rate, is essential for their conservation. Non-invasive methods, including stereo-image measurements, have been used to measure the body length of the species over the years, which aggregates in coastal areas during specific life stages. This method enables us to estimate fish length by recording the target using a stereo camera, which commonly consists of two cameras. However, measurement errors increase in the setup as the target moves away from the camera. Therefore, we conducted a multi-stereo video shoot of a free-swimming whale shark in an aquarium tank and compared the performance of stereo cameras using two, three, and four cameras. The setups with three and four cameras outperformed the traditional two-camera stereo setup in terms of precision and accuracy, suggesting that a multi-stereo camera system can effectively estimate the body length of large animals such as whale sharks from a considerable distance.
Keywords: whale shark; length estimation; conservation; three-dimensional video analysis whale shark; length estimation; conservation; three-dimensional video analysis

Share and Cite

MDPI and ACS Style

Yamamoto, H.; Sasaki, A.; Kanna, T.; Mitsunaga, Y.; Torisawa, S. Estimating Whale Shark, Rhincodon typus, Length Using Multi-Stereo-Image Measurement. Fishes 2025, 10, 513. https://doi.org/10.3390/fishes10100513

AMA Style

Yamamoto H, Sasaki A, Kanna T, Mitsunaga Y, Torisawa S. Estimating Whale Shark, Rhincodon typus, Length Using Multi-Stereo-Image Measurement. Fishes. 2025; 10(10):513. https://doi.org/10.3390/fishes10100513

Chicago/Turabian Style

Yamamoto, Hiroto, Akira Sasaki, Tomoki Kanna, Yasushi Mitsunaga, and Shinsuke Torisawa. 2025. "Estimating Whale Shark, Rhincodon typus, Length Using Multi-Stereo-Image Measurement" Fishes 10, no. 10: 513. https://doi.org/10.3390/fishes10100513

APA Style

Yamamoto, H., Sasaki, A., Kanna, T., Mitsunaga, Y., & Torisawa, S. (2025). Estimating Whale Shark, Rhincodon typus, Length Using Multi-Stereo-Image Measurement. Fishes, 10(10), 513. https://doi.org/10.3390/fishes10100513

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