An integrated method for non-intrusive underwater fish measurement based on keypoint detection and stereo vision
摘要
To address the challenge of non-invasive and dynamic monitoring of fish body size in deep-sea aquaculture, this paper proposes a three-dimensional fish body measurement method based on stereo vision. A dataset of seven categories of fish keypoints was constructed, and high-precision keypoint detection in complex and dynamic underwater environments was achieved by integrating the You Only Look Once version 8n with pose estimation (YOLOv8n-pose) model. By combining stereo camera calibration with the Semi-Global Block Matching (SGBM) algorithm, a 3D coordinate fitting model was developed to estimate fish body length and height. Experimental results show that the dataset used for constructing the 3D non-intrusive fish detection model passed the normality test for body length (p = 0.027), and the 95% limits of agreement in the Bland–Altman analysis ranged from −2.1 to 3.5 cm. For height, the p-value was 0.104, and the 95% difference was within ± 1.2 cm, indicating that the method meets the precision requirements of aquaculture monitoring. The proposed method achieved a mAP@50 of 98.8%, representing a 13.2% improvement over the traditional High-Resolution Network (HRNet) model. The average relative errors in body length and height measurements were 12.76% and 11.64%, respectively, demonstrating the effectiveness and applicability of the method in intelligent aquaculture.