Abstract
A digital stereo-camera system was used for 3-dimensional monitoring of cultured Pacific blufin tuna Thunnus orientalis individuals, which were free-swimming in a net cage. The fork lengths and the length frequency distribution of tuna individuals in a net cage were estimated using the Direct Linear Transformation (DLT) method. Information obtained from stereo-images is useful for managing the growth of tuna during rearing. In this research, we are trying to develop the simple method involving a combination of DLT and a commercial image processing software to enable aquaculturists to obtain three-dimensional measurements of fish. Then, we used a digital stereo-video camera system to evaluate the precision and validity of fish size estimates determined from repeated measurements. Of the total assessed individuals swimming within a distance of <9.2m from the camera system, estimates for 100% (37/37) were found to be valid, with an error ratio (standard error/mean) of 5%. Therefore, we believed that our proposed simple non-destructive method for monitoring free-swimming fish could be very useful for aquaculture management.
