Data analysis has centered on determining and measuring 

 those parameters useful in describing flatfish behavior near 

 the footrope of moving trawl gear. Parameters for which 

 quantitative measurements were made include: distance above 

 bottom flatfish assumed during herding, distance in front of 

 footrope maintained during herding, distance in front of the 

 footrope at which point entry into the trawl was initiated, 

 herding time, and height at which flatfish passed over the 

 footrope. Qualitative evaluations were also made on the 

 manner by which flatfish entered the trawl. 



Measurements were made directly from a video screen 

 using calipers and are reported in inches as the arithmetic 

 mean + standard deviation. Measurements were taken between a 

 pointon the periphery of the fish and the corresponding 

 point on the shadow which it cast on the substrate or 

 reference point on the net. The point on the fish used for 

 these measurements was the edge of the dorsal or ventral fin 

 at the widest part of the body. The caudal fin was not used 

 because swimming action produced considerable variation in 

 measurements. Standard fish length and width measurements 

 were taken at the footrope and only on those fish which were 

 positioned so that accurate measurements could be obtained. 



Edge discrimination measurements are influenced by 

 factors such as illumination, focus, topography, contrast, 

 and individual perception. These factors make edge or 

 boundary discrimination prone to subjective interpretation 

 and variation. To minimize variation, measurements were 

 taken by only one individual. Variability of measurements 

 was assesed by taking a series of ten replicate measurements 

 on five separate fish. Measurements of height above bottom 

 were found to vary by a maximum of +0.13 inches, distance in 

 front of trawl by +0.8 inches, and height above footrope by 

 +0.3 inches. 



Another consideration in making quantitative evaluations 

 was to determine inherent distortion factors imposed by the 

 camera system and placement. Transformation from apparent to 

 actual height above bottom was made using proportionality. 

 Measurements of fish size and distance were made at a point 

 relative to the footrope and again at a reference point on 

 the footrope. Actual distance was then determined using the 

 formula: H = h' (S/s'), where H and h' are actual and 

 measured height respectively and S and s' are size of fish at 

 reference point and h' respectively. 



Width was used as the standard measurement for this 

 determination. This measurement proved to be more accurate 

 and easier to obtain than overall length because of fish 

 orientation away from the gear. Reference measurements were 



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