Untrawlable Habitat Strategic Initiative Experiment to Examine Fish Behavior toward Moving Underwater Camera Systems

The Untrawlable Habitat Strategic Initiative (UHSI) was created by the National Marine Fisheries Service Office of Science and Technology to examine currently used acoustic and optical methods for assessing fish abundance in rock or reef habitats, identify issues limiting the utility of these methods to produce information useful for stock assessment, and conduct field experiments to address these issues. One commonly used assessment method is to conduct optical fish counts using some form of a moving camera system (i.e., ROV, AUV, towed, manned) capable of measuring the sampling volume.  The UHSI conducted an experiment in the Florida Middle Grounds coral and sponge reef system to examine the behavior of snappers and groupers to moving camera systems and to determine if this behavior leads to changes in the density of fish within the sampled volume before they were counted. This was done by placing a series of observation pods, each containing a natural light stereo camera and a DIDSON imaging sonar, along a bottom longline, then navigating an ROV, AUV and the towed CBASS system by the pods. Preliminary evidence indicates that snappers and groupers react strongly to the moving optical systems, and that the resulting density estimates are too low.