Feasibility of Using Digital Photography for Environmental Monitoring of Animals in an Artificial Reef

Both acoustic and optical methods can be used for environmental monitoring of marine ranches. However, acoustic methods are more commonly used for underwater environmental surveillance. This paper presents the results of a study of the feasibility of using digital photography for monitoring the animals in an artificial reef. Animal monitoring studies enable us to characterize the behavior of aquatic animals and to derive parameters essential to further studies, such as fork length, swimming speed, and the relative orientation of fish, in addition to providing a quantitative acoustic assessment. A charge-coupled device (CCD) camera was calibrated in a laboratory tank by direct linear transformation (DLT), and then the accuracy of the three-dimensional (3D) reconstruction was tested. Grass carp (Ctenopharyngodon idella) and common carp (Cyprinus carpio) were studied to determine the parameters of fish behavior. The mean absolute deviations in x, y, and z directions were 2.0 mm, 2.2 mm, and 2.2 mm, respectively, with maximum values of 3.9 mm, 4.3 mm, and 3.5 mm, respectively. The error in estimation of fork length was about 1 cm. Our results indicated that it is possible to use digital photography for optical monitoring of a reef.