Fish Avoidance of Remote Sampling Methods in Untrawlable Habitats

Many fish communities are preferentially distributed in sensitive or high-relief untrawlable habitats, precluding trawls and other extractive gears used in fishery independent surveys.  Direct count visual surveys from mobile platforms both complement and provide an alternative to extractive gears in untrawlable habitats.  Whereas, extractive gears may have established catchability coefficients, there are scant quantitative studies on how fishes avoid mobile platforms and the importance of avoidance on abundance estimates.  The NOAA Fisheries, Untrawlable Habitat Strategic Initiative team investigated remote sampling methods for fish in untrawlable habitats.  Fish avoidance of three platforms commonly used in fishery independent surveys (remotely operated vehicles, autonomous underwater vehicles, and towed imaging systems) was examined in coral-sponge habitat in the northeastern Gulf of Mexico in August 2014.  Mounted on landers, DIDSON imaging sonars continuously measured fish abundance at three points along a transect that was repeatedly traversed by each of the mobile platforms.  Across 26 deployments, fish abundance dropped at least 15% after the first vehicle passage, with anecdotal evidence of fish habituation to multiple vehicle passes.  Analyses will resolve differences among vehicles and across fish size classes.