Abstract

Long-term monitoring of fish biomass is required to comprehend and manage marine ecosystems. Using sampling nets to estimate fish biomass is difficult due to the fact that catchability varies depending on habitat, weather, or vessel traffic. A non-lethal, cost-effective, and efficient way to observe and measure fish in areas that cannot be sampled otherwise has been demonstrated by underwater stereo cameras. However, these techniques have not yet been tested on mid-water pelagic or semi-pelagic fish. A stereo camera was designed, constructed, and tested with the intention of enhancing survey assessments of pelagic fish biomass in locations where trawl net samples cannot be collected. The stereo camera was used in a pilot test to identify and measure fish length, depth, tilt, and yaw. During an acoustic survey in the Strait of Georgia, British Columbia, five paired stereo camera deployments and pelagic midwater trawl hauls were compared.