the 34 to 36 cm fish length interval. Choosing a discard (cull) 

 point of 30 cm, it can be seen that the large mesh landed more 

 fish by numbers and weight (Table 23). The large mesh using 

 the 30 cm cull point, decreased discards by 73% by weight. 





Table 23. 



— Winter flounder landings 







Length 













interval 





Small uncovered 



Large uncovered 



(cm) 



Kg/fish 



No. 



Kg 



No. 



Kg 



10-12 



0.05 







0.0 







0.0 



13-15 



0.07 







0.0 







0.0 



16-18 



0.09 







0.0 







0.0 



19-21 



0.11 



16 



1.8 







0.0 



22-24 



0.18 



115 



20.7 



10 



1.8 



25-27 



0.23 



204 



46.9 



30 



6.9 



28-30 



0.36 



265 



95.4 



99 



35.6 



31-33 



0.45 



168 



75.6 



148 



66.6 



34-36 



0.55 



90 



49.5 



185 



101.8 



37-39 



0.77 



85 



65.5 



106 



81.6 



40-42 



0.91 



103 



93.7 



113 



102.8 



43-45 



1.14 



62 



70.7 



65 



74.1 



46^t8 



1.36 



32 



43.5 



43 



58.5 



49-51 



1.68 



8 



13.4 



16 



26.9 



52-54 



2.05 



6 



12.3 



13 



26.7 



55-57 



2.43 



3 



7.3 



6 



14.6 



58-60 



2.93 



1 



2.9 







0.0 



61-63 



3.42 







0.0 







0.0 



Totals 



1,158 



599.2 



834 



597.9 



Landings (discard < 30 cm) 558 434.4 695 



553.6 



Discards 600 165.0 139 



44.3 



% discards 51.8% 27.5% 16.6% 



7.4% 



% reduction in discards between mesh sizes: 73% by weight. 





American Plaice 



The results in this section represent the data from 32 tows 

 made during Experiment Two. The total catch consisted of 

 3,798 American plaice. A visual inspection of Figure 13 shows 

 the length-frequency distribution between the two vessels to be 

 about the same. Some masking was evident in the large 



11 14 17 20 23 26 29 32 35 38 41 44 47 50 53 56 59 CM 



covered cod ends, but with the large number of small fish 

 caught, this was probably unavoidable. 



Selection data for the 99 mm covered cod end tows are given 

 in Table 24 and the corresponding selection curve is shown in 

 Figure 14. The 50% retention length of approxi- 

 mately 23.3 cm (9.2 in) gives a selection factor of 2.35. The 

 25-75% selection range is approximately 3.6 cm (1.4 in). Selec- 

 tion data for the 131 mm covered cod end tows are given in 

 Table 25 and Figure 14. The 50% retention length of approxi- 

 mately 29.5 cm (11.6 in) gives a selection factor of 2.25. The 

 25-75% selection range is approximately 6 cm (2.4 in). Selec- 

 tion data for the 99 mm and 131 mm uncovered tows are given 



Table 24. — American plaice length frequency dis- 

 tributions and percent retained for 99 mm cod end 

 covered tows — Linda B and Metacomet. 



Length 



Numbers caught 





interval 





99 mm 



Percent 



(cm) 



99 mm 



plus covers 



retained 



10-12 



1 



10 



10.0 



13-15 



12 



114 



10.5 



16-18 



22 



254 



8.7 



19-21 



26 



206 



12.6 



22-24 



58 



152 



38.2 



25-27 



87 



101 



86.1 



28-30 



67 



67 



100.0 



31-33 



36 



37 



97.3 



34-36 



24 



24 



100.0 



37-39 



20 



20 



100.0 



40-42 



16 



16 



100.0 



43^t5 



12 



12 



100.0 



46-48 



16 



16 



100.0 



49-51 



11 



12 



91.7 



52-54 



6 



6 



100.0 



55-57 



3 



3 



100.0 



58-60 



1 



1 



100.0 



Ioials 



418 



1,051 





o ._ -VA 



J I u 



17 20 23 26 



I 



32 35 38 41 44 CM 



I I 



10 

 LENGTH 



Figure 13. — Vessel comparisons — American plaice. Cod ends + covers: solid 

 line = Metacomet; dash line = Linda B. 



Figure 14. — Selection curves — American plaice. Solid circles = 131 mm 

 covered; open circles = 99 mm covered; open triangles = 131 mm uncovered. 



16 



