optomotor responses, and vision are important in understanding 

 the capture process (Harden Jones 1963; Arnold 1969, 1974; Wardle 

 1975, 1977; Ware 1978; Batty and Wardle 1979; Anthony 1981; and 

 Anthony and Hawkins 1983). This information has provided insight 

 into how fish orient within the water column and how they respond 

 to various stimuli. 



The process of fish capture by trawl gear involves a 

 complex interaction between the physical properties of the gear 

 and behavioral aspects of the fish subject to capture. 

 Generally, past approaches to the problem of increasing capture 

 efficiency have been concerned with assessing the engineering 

 parameters of the gear. The main approach used in these 

 assessments has been comparative fishing techniques, in which 

 "old" and "new" gear are fished together under the same 

 conditions. This approach has resulted in valuable information 

 on relative catching efficiencies of the different gear, in many 

 instances this information has been directly applicable to 

 commercial fishing operations. However, this approach does not 

 provide direct information about the capture process involved, or 

 on the specific factors causing the efficiency change. 

 Additionally, it is costly and time-consuming when each 

 experiment is carried out over as wide a range of conditions as 

 possible. 



Until recently, virtually nothing was known about the 

 behavior of fish in the vicinity of trawls. The major factor 

 which prevented behavioral assessments was the difficulty 

 involved in making detailed observations of fish in the vicinity 

 of moving gear. The development of more sophisticated techniques 

 of underwater observation has provided new methods to approach 

 this problem. These techniques were applied to make a 

 quantitative assessment of how flatfish are captured and the 

 potential of using this information to reduce the incidental 

 catch of Pacific halibut in domestic cod trawl fisheries. 



METHODS 



Underwater observations were carried out by the University 

 of Alaska and National Marine Fisheries Service ( NMFS ) aboard the 

 chartered commercial fishing vessels Royal Baron and Morning 

 Star . Video tapes of fish during capture by trawl gear were 

 obtained under natural light conditions using the ROV Manta 

 equipped with an Osprey OE1323 SIT camera. Fishing operations 

 were conducted using a Nor 'Eastern Trawl Bering Sea Combination 

 net fished at a depth of 20 fathoms. This trawl has a 138 foot 

 chain footrope covered with 6 inch diameter cookies and 

 intermittently spaced 14 inch diameter rubber discs. Areas of 

 operation were the Gulf of Alaska off Kodiak Island, Alaska and 

 the Bering Sea off Nunivak Island, Alaska. To date, behavioral 

 analysis has been conducted only on the video tapes supplied 

 by NMFS. 



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