Figure 1. Example images from the Deep Vision system showing ISO 12233 camera resolution test chart. Passing fish are pollack (Pollachius pollachius) and redfish (Sebastes genus, not identified to species).
New CRIMAC article in Fisheries Research
Underwater camera systems are commonly used for monitoring fish and fishing gear behaviours. More recently, camera systems have been applied to scientific trawl surveys for improved spatial resolution and less invasive sampling and to commercial fisheries for better catch control and reduced by-catch. A challenge when using cameras in demersal trawls is poor image clarity due to the door and ground gear generated sediment plume. In this study we have measured the height of the sediment plume produced by a large commercial trawl in the Barents Sea, investigated its effect on in-trawl camera image clarity and modified the trawl extension to lift the camera system above the sediment plume.
The results show that the sediment plume generated by the trawl reduced image clarity 4 – 6 m above the seabed, while at 10 m clear images were obtained. This limits the use of in-trawl camera systems unless proper measures are taken. To obtain clear images the camera system either needs to be lifted above the sediment plume, or the sediment plume must be prevented from entering the field of view of the camera.
