56 
Fishery Bulletin 1 1 1 (1) 
A 
Figure 2 
(A) Photos of the front and port side of the Delta submersible and (B) views of the front and port side of the Phan- 
tom DS4 remotely operated vehicle (ROV), the 2 survey tools that were used in 2007 off central California in our 
study of the reactions of fishes to underwater vehicles. The Delta measures 1.8 m tall, 1.1m wide (tapering to 0.4 
m at front port), and 4.6 m long. The ROV is 1.0 m tall, 1.4 m wide, and 2 m long. 
an ORE Trackpoint-II system. The ROV was propelled 
by 6 electric thrusters (2 angled and 4 perpendicular 
to the seafloor). Surveys were conducted at a target 
speed of 0.5 m/s and a target height of 1 m above the 
seafloor. Illumination was provided by two 250-watt 
Multi-SeaLite halogen lights from DeepSea Power and 
Light. 
The forward-facing video cameras on each vehicle 
were used to document fish reactions because these 
cameras had similar orientations and captured fish 
reactions in front of both vehicles. Both vehicles also 
were equipped with lasers to help the observers esti- 
mate size of fishes and their distance from the vehicle. 
The Delta submersible had a pair of parallel lasers 
