The resolution of the computed depth maps of fish in an underwater environment limits the 3D fish metric estimation. This paper addresses this problem using object-based matching for underwater fish tracking and depth computing using convolutional neural networks (CNNs). First, for each frame in a stereo video, a joint object classification and semantic segmentation CNN is used to segment fish objects from the background. Next, the fish objects in these images are cropped and matched for the subpixel disparity computation using the video interpolation CNN. The calculated disparities and depth values estimate the fish metrics, including the length, height, and weight. Next, we tracked the fish across frames of the input stereo video to compute the metrics of the fish frame by frame. Finally, the fish median metrics are calculated for noise reduction caused by the fish motions. Hereafter, the fish with incorrect measurement by the stereo camera is cleaned before generating the final fish metric distributions, which are relevant inputs for learning decision models to manage a fish farm. We also constructed underwater stereo video datasets with actual fish metrics measured by humans to verify the effectiveness of our approach. Experimental results show a 5% error rate in our fish length estimation.INDEX TERMS convolutional neural network, object tracking, object-based stereo matching I. INTRODUCTION
The ocean resources have been rapidly depleted in the recent decade, and the complementary role of aquaculture to food security has become more critical than ever before. Water quality is one of the key factors in determining the success of aquaculture and real-time water quality monitoring is an important process for aquaculture. This paper proposes a low-cost and easy-to-build artificial intelligence (AI) buoy system that autonomously measures the related water quality data and instantly forwards them via wireless channels to the shore server. Furthermore, the data provide aquaculture staff with real-time water quality information and also assists server-side AI programs in implementing machine learning techniques to further provide short-term water quality predictions. In particular, we aim to provide a low-cost design by combining simple electronic devices and server-side AI programs for the proposed buoy system to measure water velocity. As a result, the cost for the practical implementation is approximately USD 2015 only to facilitate the proposed AI buoy system to measure the real-time data of dissolved oxygen, salinity, water temperature, and velocity. In addition, the AI buoy system also offers short-term estimations of water temperature and velocity, with mean square errors of 0.021 °C and 0.92 cm/s, respectively. Furthermore, we replaced the use of expensive current meters with a flow sensor tube of only USD 100 to measure water velocity.
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