164 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



The size compositions for subareas were com- 

 bined, and thus we obtained a size composition 

 representing all of Georges Bank, for each season, 

 year, and market category. A certain amount of 

 irregularity in these curves was due to sampling 

 variations, inasmuch as only a limited sample from 

 a very large population of fish had been obtained. 

 To eliminate some of this irregularity we smoothed 

 each distribution by a moving average of three. 

 ScTod haddock 



Tables 13, 14, 15, and 16 show the size compo- 

 sitions ^ of the landings of scrod, in each of the 72 

 seasons, from 1931 through 1948. Table 17 shows 

 the size compositions of scrod by years. Table 18 

 and figure 11 show the average size compositions 

 of scrod for each season in all of the 18 years, and 

 table 19 shows the size composition of scrod that 

 were landed in the average year, and also the per- 

 centage size composition. 

 Large haddock 



Tables 20, 21, 22, and 23 show the size compo- 

 sitions of large haddock in each of the 72 seasons 

 over the 18-year period. Table 24 shows the size 

 composition of large haddock by years. Table 25 

 and figure 11 show, by seasons, the average size 



' For convenience in handling the large mass of data, we grouped all length 

 frequencies by 3-centimenter groups: Fish of the 29-, 30-, and Sl^jentimeter 

 groups were recorded as 30 centimeters, fish of the 32-, 33-, and 34-centimeter 

 groups as 33 centimeters, and so on. In graphs and tables where centimeters 

 are shown, they are shown as 30, 33, and 36 rather than 30.5, 33.5, and 36.5 

 (the true midpoints of the groups) inasmuch as the original centimeter meas - 

 urements were recorded as 29 when the midpoint was 29.5, 30 instead of 30.5, 

 31 instead of 31.5, etc. Where inches are shown in graphs, they represent 

 actual values: The inch equivalents opposite 30.5 rather than 30, opposite 

 31.5 rather than 31, and so on. 



The sizes in inches corresponding to the true midpoints of the 3-centimeter 

 groups are as follows: 



3-centimeter groups: Iiuhea 



18 cm 7.3 



21 cm _ 8.5 



24 cm _ 9.6 



27 cm 10.8 



30 cm 12.0 



33 cm _ 13.2 



36 cm 14.4 



39 cm 15.6 



42 cm 16.7 



45 cm 17.9 



48 cm 19.1 



51 cm 20.3 



54 cm 21.6 



57 cm 22.6 



60 cm 23.8 



63 cm 25.0 



66 cm 26.2 



69 cm.... 27.4 



72 cm 28.5 



75 cm 29.7 



78 cm 30.9 



81 cm 32.1 



84 cm 33.3 



87 cm... 34.4 



composition of large haddock that were landed in 

 all 18 years, and table 26 shows the size composi- 

 tion of large haddock that were landed in the 

 average year, and also the percentage size compo- 

 sition. 



LENGTH IN INCHES 



10 15 20 25 



I I I I I 1 I I I I I I I I I I I I 



30 40 50 60 70 



LENGTH IN CENTIMETERS 



Figure II. — Size compositions of scrod, large, and total 

 haddock landed from Georges Bank in the average year, 

 by seasons. 



Total haddock 



Tables 27, 28, 29, and 30, and figures 12a, 12b, 

 and 12c show the size compositions of total had- 

 dock (scrod and large combined) in each of the 72 

 seasons over the 18-year period. 



The presence of modes (figures 12a, 12b, and 

 12c), at slightly increasing sizes of fish in succeed- 

 ing seasons, suggests that each series of modes may 

 be composed largely of the same year class of had- 

 dock. In some instances these year classes (if 

 they are year classes) apparently were the chief 

 source of supply of the fishery for several succeed- 

 ing seasons, and even for succeeding years. 



These modes are more obvious if one season 

 (spring, for example) in a particular year is com- 



