566 U. S. BUREAU OF FISHERIES 
but caught witu greater certainty. These show a relatively constant yield. 
The shore fisheries are confined to a more limited area conducive to a more 
thorough exploitation. The fish in this group passed the climax of their yield 
in 1902 and since then have been taken in smaller quantities. The anadromous 
fishes are still more strictly confined to limited areas during their spawning 
runs when they are subject to intensive fishing, and their yield passed its 
climax some 10 years earlier than that of the shore fishes and has declined more 
severely. 
We can not venture too far with general conclusions of this sort, however. 
Each of the above-mentioned groups is a complex of species that must be 
examined separately. For this purpose I have prepared a number of charts. 
“oC} 

“2 
[e) 


POUND 
500 

MILLIONS OF 
300 

206 




og 
) 
= 
Fig. 6.—yYields of various groups Eetcs on the Atlantic seaboard, 1880 
to 1922 
on a logarithmic scale to show the relative changes in yield of the more im- 
portant species. The logarithmic scale reduces the curves to a convenient 
form for comparing rates of change, and in interpreting them the relative 
steepness of the slopes of the curves is the significant feature. Thus, if in a 
given period the yield of a spez_es increases from 5,000,000 to 10,000,000 pounds, 
a 100 per cent increase, and another species increases from 12,000,000 to 
24,000,000, also a 100 per cent increase, the slopes of the two curves will be 
the same. In other words, logarithmic plotting expresses the percentage 
increase or decrease. 
Among the pelagic fishes (fig. 7), menhaden and mackerel fluctuate so much 
that it is difficult to say whether the trend is upward or downward. It seems 
slightly upward in the case of menhaden and slightly downward in the case of 
