A total of 29 separate observations in front of the 

 footrope and 15 observations behind the footrope were used to 

 calculate a visual response field for fish exhibiting capture 

 sequence A (Fig. 4). This visual response field is based on 

 the maximum measured distance of the initial entry sequence 

 and the position behind the footrope where fish righted 

 themselves. Angles were calculated between the direction of 

 travel and the top of the roller gear. This entry sequence 

 was initiated (point at which the fish began its flip) at a 

 visual angle less than or equal to 155°. After passing the 

 footrope fish righted themselves at a visual angle between 

 130° and 162°. 



The second type of entry sequence exhibited by flatfish 

 (sequence B in Fig. 5) differed significantly. This behavior 

 sequence was exhibited by 20 percent of the fish observed. 

 In this sequence fish would rise to a height of between 14 

 and 39 inches above the footrope (average 23.5 inches +6.6 

 inches) and either swim with the footrope allowing it to 

 overtake and pass beneath the fish or turn through 180° 

 within the horizontal plane and swim into the net (Fig. 5). 

 The distance in front of the footrope at which this sequence 

 was initiated was between 24 and 47 inches (average 30.9 

 inches +6.3 inches). The length of the flatfish exhibiting 

 this sequence was between 8 and 21 inches with a mean of 15.2 

 inches +4.8 inches. 



A total of 13 fish exhibiting entry sequence B were 

 observed during herding and entry to determine the visual 

 response field of fish exhibiting this type of entry sequence 

 (Fig. 6). The angle at which these fish initiate trawl entry 

 was between 152° and 164°. After crossing the footrope the 

 fish did not exhibit any unusual responses which would permit 

 an analysis of the limit of visual contact with the footrope. 



The mean length of fish exhibiting the two entry 

 sequences were tested to determine if the entry sequences 

 were size dependent. The t-test was used to test the null 

 hypothesis H : u^=U2. Based on this test the null 

 hypothesis was accepted tg. 05( 2 )45 = < - ) * ^3 and -^ is concluded 

 that the entry sequences are nor size dependent. 



DISCUSSION 



The behavior of flatfish during herding and capture by 

 trawl gear has not been described in detail. Main and 

 Sangster (1981b) gave a brief description of flatfish 

 encountering the sweeps and footrope of trawl gear. They 

 reported a tendency for flatfish to be herded at 90° to the 

 sweeps. During herding, fish would move away from the sweeps 

 for some distance then settle back to the substrate. When 

 the sweeps approached, the process would be repeated 



413 



