Table 4. — Atlantic cod length frequency distribu- 

 tions and percent retained for the large-mesh (135 

 mm overall average) covered tows — all vessels. 



Table 5. 



Atlantic cod length frequency distributions and percent retained 

 from uncovered cod end tows — all vessels. 



Length 



Numbers caught 





interval 





135 mm 



Percent 



(cm) 



135 mm 



plus covers 



retained 



10-12 







3 



— 



13-15 







6 



— 



16-18 



1 



25 



— 



19-21 







49 



— 



22-24 



1 



46 



— 



25-27 







44 



0.0 



28-30 



1 



50 



2.0 



31-33 



2 



71 



2.8 



34-36 



7 



71 



9.9 



37-39 



12 



61 



19.7 



40-42 



13 



60 



21.7 



43-45 



20 



59 



33.9 



46^8 



21 



32 



65.6 



49-51 



19 



26 



73.1 



52-54 



19 



26 



87.1 



55-57 



27 



31 



94.2 



58-60 



49 



52 



95.8 



61-63 



46 



48 



100.0 



64-66 



54 



54 



100.0 



67-69 



73 



73 



100.0 



70-72 



94 



94 



98.2 



73-75 



55 



56 



100.0 



76-78 



60 



60 



100.0 



79-81 



43 



43 



100.0 



82-84 



29 



29 



100.0 



85-87 



12 



12 



100.0 



88-90 



11 



11 



100.0 



91-93 



5 



5 



100.0 



94-96 



12 



12 



100.0 



97-99 



— 



— 



— 



100-102 



7 



7 



100.0 



103-105 



4 



4 



100.0 



106-108 



3 



3 



100.0 



109-111 



1 



1 



100.0 



135 



1 



1 



100.0 



Totals 



702 



1,225 





Length 

 interval 



Numbers 



caught 



B 



A 



% retained by 

 135 mm 

 B x 100 



(cm) 



(A) 105 mm 



(B) 135 mm 



1. 6 A 



10-12 











0.00 



0.0 



13-15 











0.00 



0.0 



16-18 











0.00 



0.0 



19-21 



1 







0.00 



0.0 



22-24 



1 







0.00 



0.0 



25-27 



5 







0.00 



0.0 



28-30 



16 



1 



0.06 



3.9 



31-33 



31 



2 



0.06 



4.0 



34-36 



64 



4 



0.06 



3.9 



37-39 



83 



12 



0.14 



9.0 



40-*2 



124 



14 



0.11 



7.0 



43-45 



99 



22 



0.22 



13.9 



46-48 



59 



30 



0.51 



31.8 



49-51 



60 



33 



0.55 



34.4 



52-54 



61 



55 



0.90 



56.4 



55-57 



51 



60 



1.18\ 



73.5 



58-60 



61 



80 



1.31 



I 82.0 



61-63 



58 



88 



1.52 1 



94.8 



64-66 



50 



106 



2.12 1 



132.5 



67-69 



58 



108 



1.86 ' 



[Avg. H6.4 



70-72 



63 



109 



1.73 | 



f 1-60 108.1 



73-75 



55 



106 



1.93 



120.4 



76-78 



44 



60 



1.36 



85.2 



79-81 



33 



49 



1.48 1 



' 92.8 



82-84 



15 



23 



1.53,/ 



95.4 



85-87 



17 



12 



0.71 



44.1 



88-90 



7 



12 



1.71 



107.1 



91-93 



8 



8 



1.00 



62.5 



94-96 



8 



7 



0.88 



54.7 



97-99 



5 



1 



0.20 



12.5 



100-102 



1 



5 



5.00 



312.5 



103-105 



3 



1 



0.33 



20.8 



106-108 



2 



5 



2.50 



156.3 



109-111 



2 



2 



1.00 



62.5 



112-114 



1 



1 



1.00 



62.5 



121-123 



I 







0.00 



— 



135 



1 







0.00 



— 



Totals 



1,148 



1,016 



(1971). It is also interesting to note that in each experiment the 

 selection factor determined for the large mesh size was greater 

 than that found for the small mesh. This may indicate a 

 nonlinearity in the selection factor for Atlantic cod similar to 

 that found by Clark (1963) for silver hake. However, there was 

 no appreciable difference in selection range between the two 

 mesh sizes which in each case was about 9 cm. 



Atlantic cod girths were taken randomly throughout the ex- 

 periment and found to have little variance from the published 

 means for girth-length ratios. The girth-length relationships 

 from Margetts (1957) and later confirmed by Messtorff (1958) 

 are represented by the following equations: 



length = natural girth x 1 .95 



length = (constricted girth x 2.03) + 0.7. 



Most of the sample girths during this series of experiments fell 

 close to the range indicated by the above two equations (Fig. 

 4). 



Table 6 demonstrates an interesting point. For the combined 

 catch during the experiment the large mesh outfished the small 



1A 



55 



544 



IB 



55 



843 



IB 



55 =1.55 

 1A 



55 



mesh, on a weight comparison basis, in all conditions: no 

 discard, 42 cm (16 in) discard, and 52 cm (20 in) discard 

 lengths. 



Haddock 



The tables and graphs in this section represent the data from 

 24 tows made during the third experiment. The total catch con- 

 sisted of 4,463 haddock. Looking at the length frequency 

 distributions (Table 7) of the haddock from cod ends and 

 covers, it can be seen that both vessels and both size cod ends 

 sampled the same populations. This is further demonstrated in 

 Figure 5. Reviewing the "cod ends only" distributions, 

 "masking" can be detected when comparing the 138 mm 

 covered cod ends with the 138 mm uncovered; a higher percen- 

 tage of smaller fish were caught in the former. 



