Effects of simulated underwater vehicle lighting on fish behavior

Abstract

Little is known regarding bias attributable to fish behavior for visual transects con- ducted using underwater vehicles (UVs). Experiments were conducted under 2 ambient illuminations to assess the behavioral responses of 7 north Pacific Ocean groundfish species to a light stimulus that simulated the approach of a UV. Species included sablefish Anoplopoma fimbria, Pacific halibut Hip- poglossus stenolepis, lingcod Ophiodon elongatus and 4 species in the genus Sebastes: blue rockfish S. mystinus, black rockfish S. melanops, copper rockfish S. caurinus and quillback rockfish S. maliger. Movement, as well as general activity, varied greatly between species. The most active spe- cies, sablefish, became agitated and moved away from the looming light source, while the least active species, Pacific halibut and lingcod, typically remained stationary. Of the 4 rockfish species, 2 demonstrated a strong response to ambient light level. Black rockfish and blue rockfish moved away from the looming light source, but avoidance was delayed under high ambient light. Bias probably differs among species, being greatest for those that are highly active and mobile, like sablefish. Fur- ther, ambient light may modulate bias, such that researchers need to be cautious about comparing results for surveys conducted at different depths and/or times of day.