WIEBE ET AL.: AVOIDANCE OF TOWEL) NETS BY NKMATOSCKL1S MEGALOPS 



RING BOB 



6 

 \ 



S 





01 - 



MOC I 62 



MOC 1-63 N 



MOC 1-27 D 



I I I M I I I I I M I I 



MOC 10 28 N 



' 



MOC 10 35 D 



RING EMERSON 

 STATION 6 



MOC I 99 



OCTOBER/NOVEMBER KNORR 71 



STATION 9 

 MOC 1-117 D 



MOC 10-59 



m <| I I I i 



IJ1 



I 



MOC 1-102 



MOC 10-58 N 



i i i i i i i i 



MOC 1-103 N 



RING FRANKLIN 



MOC 1-109 



TT 



- 



MOC 10-61 



50 100 150 



MOC 10-62 N 



50 WO 150 



MOC 10 65 



WET WEIGHT (mg) 



MOC 10 36 



''''' i i i i I i i j 



SLOPE WATER 



MOC 1 116 N 



TV 



MOC l-IIO N 



MOC 10-66 N 



' ' ' ' ' ' ' i i i i i i . i i i i 

 50 100 150 



STATION 4 

 MOC 1 75 N 



IMF 



MOC 10 38 N 



j j i i i i 



STATION 5 



MOC 1-97 N 



MOC 10-57 N 



i I i L I M I I I I I I 



50 100 150 



0- DAY 

 N' NIGHT 



Figure 5.— Comparison of the difference between paired MOCNESS 1 and MOCNESS 10 catches in No./l,000 m 3 for a given wet 

 weight interval. For shaded columns above the line, the MOCNESS 1 catch is greater than the MOCNESS 10 catch and vice versa 

 for crosshatched columns below the line. 



tion derived by Barkley (1972, equation 6) 

 wherein: 



10 m 2 MOCNESS catch 

 volume sampled 



Pc = 1 



Jo u,. 



R(lf 



u e 2 ) Vi 



(2) 



This expression assumes that as the net moves 

 forward through the water, an individual senses 

 the oncoming net and at a distance Xo in front of 

 the net begins a swimming response in a direc- 

 tion away from the net which is optimal for 

 avoidance. Thus, this equation provides an esti- 

 mate of the minimum probability of capture. 



As a first step in applying these equations to 

 our data, we may recall that for both the paired 

 night tows and the paired day tows differences 

 between the two net systems were not signifi- 

 cant, i.e., 



1 m 2 MOCNESS catch 

 volume sampled 



If we assume that the number of organisms per 

 unit volume was a constant during the time each 

 pair of tows was taken, then: 



10 m 2 MOCNESS P, = 1 m 2 MOCNESS P r 



and 



1 - 



XloUe 



2\'/ 



i50(ioo' -u;) 



X\U f 



2\ </., 



50(100' - uf) 



83 



