48 U. S. BUREAU OF FISHERIES 
far greater relative abundance by long hauls than by pound nets. 
The same kind of size selection is shown by the catch of spots in 
Figure 11. If ages are assigned provisionally to the prominent size 
groups as shown in the graph, it is apparent that the I[I-group is 
taken far more abundantly in the early part of the season by long- 
haul seines than by pound nets. As the I and II groups grow, how- 
ever, increasing amounts are taken by the long hauls until in October, 
BUTTERFISH, STATION A’ 
NG 
bene) JUNEIZ2 , JUNEZO , JUNE26,. TOTAL , PERCENT 
222 
zz 
ay 
OONIHDULRWN—-OOD= 
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wie = 
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PERCENT OF TOTAL NUMBER 


= 
FOSS 2S eases 
TOTAL LENGTH OF FISH. 

Fic. 7.—Illustrating method of tabulating length frequencies and con- 
structing curves. At station A 35 butterfish contained in the gross 
sample obtained from the pound-net catch of one crew were measured 
and their lengths tallied on the record sheet opposite the correponding 
length in centimeters, as in the first column. On succeeding visits 
to this station (on June 12, 20, and 26) the butterfish taken were 
measured and tabulated. The total number of fish occurring at each 
centimeter length was then determined by adding together the samples, 
as shown in the total column. The number of fish at each length was 
reduced to a percentage of the total number, as shown in the per cent 
column, and comprise a length-frequency table corresponding to 
Tables 3 to 11. These figures were then used to plot the curve here 
shown by placing points at the corresponding heights on the vertical 
scale over the proper lengths on the horizontal scale. Fictitious and 
not actual figures have been used in this illustration 
when the majority of the fish are above 15 centimeters in length, 
virtually equal numbers of the I and II groups are taken by both 
gears. 
Figure 12 illustrates the catch of croakers. As was said before, the 
separate-age groups can not be distinguished readily, but it is again 
apparent that the larger fish are taken more abundantly by long- 
haul seines throughout July, August, and September, and that the 
smaller group appears in numbers only when the fish have grown 
beyond 19 centimeters in size. 
