FISHERY BULLETIN: VOL. 74, NO. 3 



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FiGURE 13.-The positions of each of the 

 six fishes (small circles) and their means 

 (large circles). The arrowheads indicate 

 the directions of travel of the group. 

 These lines pass through the means and 

 the transverse lines intersect to divide 

 the field into quadrants. 



Also shown is the pattern of each fish's distribu- 

 tion, together with the means/ the momentary 

 swimming direction of the school, and a line at 

 right angles to it intersecting at the mean posi- 

 tion. This device divides the area in which the 

 fishes occur into quadrants. The data for this are 

 given in the first part of Table 1. The precise 

 positions of the fishes were picked from Hunter's 

 (1966) figure 2 and have been handled by graphic 

 methods in the construction of the diagrams 

 shown in Figures 13 and 14. The numerals attend- 



'These means were obtained by separately spreading each of 

 the eight positions of the six fishes on Cartesian graph paper and 

 determining their X and Y values and the means. 



ing the positions of the fishes, actually the tips of 

 their snouts, in Figures 12, 13, and 14 are those 

 used by Hunter (1966) to differentiate the in- 

 dividuals and they have no other significance here. 



It is immediately apparent that fish number 6 is 

 in the front quadrants continuously. Replotting 

 this data according to the total number of each fish 

 separately as in Figure 14A, other features ap- 

 pear. Figure 14B, which shows the means of 

 Fig^ure 14A, does indeed approximate the Weihs 

 (1973a) diamond. 



Considering the manner in which the data have 

 been assembled— captive fishes in a tank, the 

 curvature of their paths, the difficulties in es- 

 timating the path of the school, and its generally 



Figure 14.-The location of each of the 

 six fishes (small circles) at each of the 

 eight positions. A. The larger light 

 circles with the intersecting lines pass- 

 ing through them are those shown in 

 Figure 13. The large dark circles show 

 the locations of the mean positions of 

 each of the six fishes. B. The large light 

 circles represent the means of the six in 

 A. The small circles show the mean 

 position of each fish (the dark circles of 

 A). 



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