Using dual- frequency sonar to detect juvenile Goliath grouper

Juvenile E. itajara in mangrove undercut (DIDSON). This video includes the DIDSON frame from Fig. 2. Here, undisturbed swim and resting behavior can be observed. The DIDSON video stream begins with a long shot of a mangrove undercut. A juvenile E. itajara enters the field of view (FOV) at the 1.5 m marker on the right of the image, and remains in the area delimited by the 1.5 m a 2.0 m markers at either side of the FOV. At time 44 s a second E. itajara enters the FOV at the 1.5 m marker on the left side of the image, remaining parallel to the first fish, and then exits the FOV on the left side along the 2.0 m marker at time 1 m 12 s. The remaining E. itajara exits the FOV on the right side below the 2.0 m marker at time 1 m 15 s.