874 



Fishery Bulletin 97(4), 1999 



blooms. Camera equipment was deployed 45 times, 

 primarily off the northern and northwestern shores of 

 the Queen Charlotte Islands (Fig. 1). Bottom habitat 

 ranged from mud or soft sediment, gravel, cobbles, or 

 large boulders, to steep ledges. Deployments were in- 

 tended to last about one hour Problems with strong 

 currents or the loss of four or more baits due to fish 

 captures or other reasons resulted in early gear retriev- 

 als._Longer deployments resulted from gear retrieval 

 problems. Time on bottom for each deployment aver- 

 aged 58 min (range 14—150 min, SD 28 min). Average 

 depth for all sets was 67 m (range 11-84 m). 



Equipment 



A silicone-intensified tube (SIT) monochrome video 

 camera (model OE1323, Osprey Electronics Ltd., 

 Aberdeen, Scotland) was housed in an enclosure fea- 

 turing both pan and tilt functions. This enclosure 

 was mounted in an aluminum cage connected by 5-cm 

 aluminum pipe to a square base frame constructed 

 of 5-cm steel pipe (Fig. 2). The camera-frame assem- 

 bly was deployed by, and monitored through, an elec- 

 tromechanical cable. All observations were made by 

 using ambient available light. 



53 30' N 



52 30'N 



134° W 



I 



133 W 



I II Obser\ anon areas 



\'orth Pacific Ocean 



A 0.8-cm (5/16-inch) diameter groundline was sus- 

 pended about 30 cm inside the base frame by short 

 lengths of elastic cord attached to the inside corners 

 of the steel frame. This arrangement resulted in an 

 elastic attachment for the hooks and gangions. This 

 "soft" attachment was probably a more realistic 

 model of the behavior of a gangion on a groundline 

 than an attachment made directly to the rigid steel 

 frame. The study used 16/0 circle hooks (O. Mustad 

 and Sons, Oslo, Norway, Quality 39965), the size and 

 style most commonly used in the Pacific halibut fish- 

 ery, and the standard in IPHC surveys. Hooks were 

 attached by 81-cm (32-inch) gangions and snaps to 

 the suspended groundline, one per side alternating 

 with two per adjacent side, for a total of six hooks. 

 All hooks were baited with 0.17-kg (1/3-lb) pieces of 

 chum salmon iOncorhynchus keta) fillet with skin 

 intact. 



Observation of a 25-cm length of flexible surveyor's 

 tape attached to one of the aluminum legs, as well 

 as of dust or sediment plumes during bait attacks, 

 was used to determine the direction of bottom cur- 

 rent and also as a qualitative measure of current 

 strength. The video signal was monitored and re- 

 corded at all times. When viewed directly from above, 

 all parts of the square base were 

 131 w within the field of view. This usu- 

 ^ ally meant that all six hooks could 



be viewed at the same time. When 

 one or more hooks lay outside the 

 base frame, the camera was periodi- 

 cally redirected for viewing these 

 outside hooks. 



Cli 



Figure 1 



Location of camera deployments. Box in inset shows general area of 

 operation. 



Fish length and distance 

 measurements 



Lengths of 20 hooked and landed 

 halibut were measured. During 

 video editing, relative fork lengths 

 for all halibut that could be clearly 

 viewed on or near the bottom and 

 at or near the center of the frame 

 were obtained by using a vernier 

 caliper held against the video screen 

 while the video image was frozen. 

 The linear regression between mea- 

 sured and relative fork length (/•= 

 0.74) was used to estimate the fork 

 lengths of 92 fish not captured and 

 retrieved, as well as the distance fi'om 

 fish lying on the bottom to the near- 

 est baited hooks. Caught fish, other 

 than halibut, were weighed to the 

 nearest 0.5 kg on a spring scale. 



