196 
BULLETIN OF THE BUREAU OF FISHERIES 
surface of the sea may be scattered sparsely through a great depth or concentrated 
in a shoaler stratum, depending both on the depth of water at the station in question 
and on whether they are more or less stratified or are evenly distributed from the 
surface downward. 
In spring the latter state may be said to apply generally down to 175 meters; 
and assuming that practically the whole catch (in the case of the deeper hauls) was 
made above that level, as seems justified for the reasons outlined above (p. 24), 
we arrive at an average of about 48 Calanus per cubic meter for March, 1920, and 
69 for April, with extremes of 1 to 654 and 4 to 624, respectively, for these two months. 
Thus it seems that a slight general increase took place from March to April, cor- 
Fig. 67. — Numbers of the copepod Calanus finmarcliicus per cubic meter of water in May and June, 1915, as calculated 
from the vertical hauls, assuming that all were living shoaler than 175 meters depth 
responding to the beginning of the vernal wave of reproduction of the species, but 
irregularly from station to station and reversed at many stations, without apparent 
correlation between the relative density of aggregation and the depth of water or 
the locality in the gulf. 
As might be expected, the great increase in abundance of this copepod which 
takes place in May is accompanied by a corresponding increase in the numbers 
present per cubic meter to an average of about 500 for all the May and June stations 
of 1915 and 1920 combined (fig. 67) — that is, to more than seven times the April 
average— and with a well-defined cleavage into “rich” and “poor” regions. In the 
Western parts of the gulf and along a line toward Cape Sable Calanus then averaged 
