Quantifying the behavior of fish in response to a moving camera vehicle by using benthic stereo cameras and target tracking Fishery Bulletin

Underwater cameras increasingly are being used on remotely operated, autonomous, or towed vehicles to provide fishery-independent survey data in areas unsuitable for bottom trawls. To observe and quantify avoidance and attraction behaviors of fish to these vehicles, we developed an observational test bed consisting of 3 benthic stereo cameras, set in a straight line, on a coral reef in the Gulf of Mexico. During one pass of a towed camera vehicle, one of the benthic cameras viewed a school of vermilion snapper (Rhomboplites aurorubens) that exhibited a variety of avoidance behaviors. Stereo analysis was used to position some these fish, and target tracking was used to estimate their swimming performance and schooling characteristics for each second from the time the research vessel had passed the benthic cameras to the time of arrival of the towed underwater vehicle. The fish showed little reaction to the tow vessel but responded to the tow cable by swimming laterally and downward, then rapidly increased their swimming speed and avoidance behavior when the towed vehicle came into view. The use of observational test beds, stereo photography, and target tracking allows quantification of the avoidance response and provides a means to determine which stimuli produced by the sampling process elicit fish avoidance behaviors.