steel with square mesh openings of 100*/ along 

 a side (diagonal of 140//). A rubber cap fits 

 under the screened bottom of the cod end to 

 keep it from clogging during a period of 

 straining. Removal of the cap after a period of 

 straining allows residual water in the funnel, 

 about 1.5 liters, to drain through the cod end. 



Estimates of the sizes of organisms that are 

 retained by the screening were obtained in two 

 trials. In each trial three types of samples 

 were collected after a short period of strain- 

 ing: (a) organisms that passed through the cod 

 end after the cap was removed; (b) organisms 

 that were retained in the cod end; and (c) 

 organisms that were washed off the screening 

 of the funnels with a spray gun. All organisms 

 passing through the cod end (sample type (a)) 

 were counted and measured for maximum width 

 excluding appendages. Numbers in the other 



types of samples were estimated from one- 

 fourth aliquots. The two trials gave such 

 similar results that they were pooled. They 

 are summarized in three histograms of width 

 composition (fig. 4.). 



Comparison of the histograms for organisms 

 that passed through the cod end (type a) and 

 those that were retained (type b) reveals that 

 only organisms wider than 100// are effectively 

 retained by the 100// mesh. The number of 

 organisms passing through the cod end declines 

 abruptly above the 80 to 100// category but the 

 number of organisms retained on the screening 

 of the cod end does not show this change. 



Comparison of the histograms of or- 

 ganisms that were retained by the cod 

 end (type b) and those that were washed 

 off the screen with a spray gun (type 

 c) shows that the width compositions of 



W 



80 r 

 60 

 40 

 20 







mi 



J ' ■■' '■' " I L. 



-I I I 



V) 



z 1000 



< 



o 



a: 800 



o 



600 

 O 400 



at 200 



UJ 



S ° 



z> 

 z 



600 r 

 400 

 200 

 



n 



JIZL 



40 



80 



120 



160 200 240 280 



320 



WIDTH (MICRONS) 



Figure 4. — Width composition of animals that: (a) pass through the screening of the cod end, (b) are retained 

 on the screening of the cod end, and (c) adhere to the screening of the funnel. All screening had 100// mesh 

 openings. Histogram (a) was constructed from total counts and (b) and (c) were estimated from one-fourth 

 aliquots. 



