There are supplementary videos available for an article appearing in the forthcoming ESR Special: Range-wide status and conservation of the Goliath grouper

 

Frias-Torres S, Luo J

Using dual-frequency sonar to detect juvenile goliath grouper Epinephelus itajara in mangrove habitat

ESR 7:237-242 | Full text in pdf format

 

Video 1 (.wmv, 12.8 MB)
Juvenile E. itajara in submerged dead tree (DIDSON). This video includes the DIDSON frame from Fig. 1. Three juvenile E. itajara are shown in the area delimited by the 1.5 m and 2.0 m markers at either side of the field of view (FOV). One of the juveniles comes in and out of focus. At time 1m 6s, the image zooms and E. itajara are shown at the top of the image (markers 1.5 m and 2.0 m in FOV), while grey snapper Lutjanus griseus swim at the bottom of the image (markers 1.0 and 1.5 m in FOV). At time 1m 42 s the image zooms again for a final close-up of the three E. itajara juveniles.

 

Video 2 (.wmv, 3.1 MB)
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.

 

Video 3 (.wmv, 6.1 MB)
Diver with video camera encounters juvenile E. itajara in mangrove undercut (DIDSON). Here, DIDSON works as a third observer, recording juvenile E. itajara reaction in the presence of divers from Talbot Films, equipped with professional underwater cameras and lights. The video stream begins with a long shot of a mangrove undercut, and several juvenile E. itajara drifting in the current and returning to their initial positions throughout the field of view (FOV). At time 16 s the front element of the underwater video camera enters the FOV on the left side, between the 2.5 m and 3.0 m markers. At first, E. itajara flee the FOV but then return to inspect the diver. At time 50 s the camera appears to exit the FOV on the left side, but the diver remained just out of DIDSON reach. The juvenile E. itajara continue to remain curious about the diver, until he moves away from the site, marked by a plume of drifting sediment starting at time 1 m 12 s.