Novel Cannibalism Indices of Grouper Juvenile in High-Density Aquaculture using Density Map and Optical Flow
Journal
2025 Asabe Annual International Meeting
Date Issued
2025
Author(s)
Abstract
Groupers are widely distributed in tropical and subtropical seas, contributing approximately $1.4 billion annually to Taiwan's aquaculture industry. In Taiwan, intensive and phased farming strategies are commonly used. However, during the intermediate nursery stage, cannibalism among juvenile fish often results in significant economic losses. To address this, the study proposes a method to develop a cannibalism assessment index for juvenile grouper populations using density maps and optical flow techniques. Juvenile grouper images were captured with a Raspberry Pi camera at a density of 100 fish, and a one-week video dataset was prepared. Using the YOLOv8, density maps were generated to predict spatial fish distribution, and optical flow methods estimated pixel intensity changes to calculate motion characteristics, such as speed and angular velocity. These analyses were combined to establish a cannibalism assessment index. Results showed that under high-density conditions (1,000 fish per ton of water), the mean absolute error (MAE) and root mean square error (RMSE) for fish counting were both below 6%, confirming model accuracy. The density maps correctly predicted fish distribution, while optical flow revealed distinct motion vector angles linked to cannibalism. Incorporating momentum further quantified cannibalistic behavior. This study has significant potential for application during the intermediate nursery stage of juvenile grouper cultivation. The findings not only enable accurate estimation of fish counts in high-density conditions but also highlight how the establishment of a cannibalism assessment index can enhance the understanding of fish behavioral patterns in practical aquaculture environments, thereby contributing to the advancement of "smart aquaculture".
Event(s)
2025 American Society of Agricultural and Biological Engineers Annual International Meeting, ASABE 2025
Subjects
Behavioral Indicators
Cannibalism
Density Map
Juvenile Hybrid Grouper
Optical Flow
Publisher
American Society of Agricultural and Biological Engineers
Description
2025 American Society of Agricultural and Biological Engineers Annual International Meeting, ASABE 2025, oronto, Ontario, Canada July 13-16, 2025
Type
conference paper