used to determine the selection of the small cod end due to lack 

 of small fish. Selection data for the 138 mm covered cod end 

 tows are given in Table 17 and Figure 10. The 50% retention 

 length of about 45 cm (17.7 in) gives a selection factor of 3.26. 

 Selection data for the 107 mm and 138 mm uncovered tows are 

 given in Table 1 8 and Fig. 10. A 50% retention length of 46 cm 



Table 17. — Pollock length frequency distributions 

 and percent retained for 138 mm cod end covered 

 tows — both vessels. 



Length 



Numbers caught 





interval 





138 mm 



Percent 



(cm) 



138 mm 



plus covers 



retained 



37-39 







2 



0.0 



40-42 



1 



11 



9.1 



43-45 



17 



37 



45.9 



46^8 



48 



87 



55.2 



49-51 



78 



115 



67.8 



52-54 



64 



83 



77.1 



55-57 



42 



50 



84.0 



58-60 



47 



48 



97.9 



61-63 



24 



24 



100.0 



64-66 



28 



28 



100.0 



67-69 



15 



15 



100.0 



70-72 



2 



2 



100.0 



73-75 



2 



2 



100.0 



76-78 











100.0 



79-81 



1 



1 



100.0 



82-84 











100.0 



85-87 



1 



1 



100.0 



Totals 



370 



506 





100 



, ._._.__ 





// 



80 



'/ 



RETENTION 

 J O 



..Jl- - - - - - 



o^ 



• 1 



40 



// 



20 

 



1 1 it 1 1 ' ' ' 1 ■ - 



Table 18. — Pollock length frequency distributions and percent retained for the 

 138 mm uncovered cod end compared with (he 107 mm uncovered cod end — 

 both vessels. 



Length 











interval 



Numbers 



caught 



B 

 A 



B x 100 



(cm) 



(A) 107 mm 



(B) 138 mm 



2.9/1 



37-39 



1 







0.00 



0.0 



40-42 



5 



1 



0.20 



6.9 



43-45 



13 



7 



0.54 



18.6 



46-48 



23 



34 



1.48 \ 



51.0 



49-51 



40 



91 



2.28 



78.4 



52-54 



21 



78 



3.71 



128.1 



55-57 



21 



78 



3.71 1 



128.1 



^4 ™ 

 206.9 



58-60 



15 



38 



2.53 ' 



61-63 



4 



24 



6.00 



64-66 



5 



15 



3.00 



103.4 



67-69 



4 



5 



1.25 



' 43.1 



70-72 



2 



5 



2.50/ 



86.2 



73-75 



2 



1 



0.50 



17.2 



76-78 



1 



4 



4.00 



137.9 



79-81 



1 



3 



3.00 



103.4 



82-84 



1 



3 



3.00 



103.4 



85-87 



1 







— 





88-90 



2 







— 





91-93 







3 



— 





94-96 











— 





97-99 











— 





100-102 



2 







— 





Totals 



164 



390 



120 





102 







1A = 



122 



IB = 



348 



B . 



49 





49 





A 



2.85 



(18.1 in) is obtained for the 138 mm cod end which gives a 

 selection factor of 3.33. It is interesting to note that the same 

 large covered tows showed a definite masking effect in regard 

 to haddock during this experiment but it did not show up for 

 pollock. The larger cod end caught fewer small fish (Fig. 11). 



26 32 38 44 50 56 62 68 74 CM 



25 



- 









20 





/ i * 



i 



i 

 i 





15 



- 





i 

 i i 

 I i 



\ t 

 ' \ ' 





1C 







\ * I 

 \ -.» 



■Ai 





5 





if 











i — 1 <« | | 





-w-'L- 1 



26 32 38 44 50 56 62 68 74 80 86 92 98 CM 



10 



15 



20 



LENGTH 



IN 



25 

 LENGTH 



Figure 10. — Selection curves — pollock. Solid circles = 138 mm covered; solid 

 circles in triangles = 138 mm uncovered. 



Figure 11. — Catch distributions — pollock. Solid line = cod ends + covers; 

 dash line = 138 mm cod ends; dot line = 107 mm cod ends. 



14 



