262 
BULLETIN OF THE BUREAU OF FISHERIES 
Station 
Date 
Number of 
Metridia 
lucens per 
square 
meter 
Depth 
in meters 
Station 
Date 
Number of 
Metridia 
lucens per 
square 
meter 
Depth 
in meters 
10278 
May 14,1915 
Aug. 6, 1915 
Oct. 9, 1915 
26, 250 
23, 450 
17, 100 
150-0 
200-0 
60-0 
10333 .. 
Oct. 22,1915 
May 4, 1920 
16, 300 
16, 500 
80-0 
48-0 
10304 
20120 
10328 
These average numbers of this copepod per square meter, calculated from the 
vertical hauls, do not suggest that the strata of water below 150 to 200 meters added 
appreciably to the catches, although not enough deep hauls were made for a positive 
assertion. 
Depth of vertical hauls 
Between 30 and 100 meters.. 
Between 101 and 199 meters. 
Deeper than 200 meters 
Average 
number 
per 
square 
meter 
2, 750 
3, 136 
2,562 
Local breeding and immigration. — No direct observations have been made on 
whether or to what extent M. lucens spawns in the Gulf of Maine. Consequently, its 
geographic and seasonal distribution is the only basis on which to judge whether 
the local stock is chiefly the result of local reproduction or depends upon immigration 
from richer centers of propagation for its maintenance. The regularity of occur- 
rence and comparative abundance of the species within the gulf is a strong argument 
that it is regularly native there. Its regularly increasing numbers during the spring 
and the pronounced augmentation in its numerical strength in September and 
October likewise point to vernal and autumnal waves of propagation. However, 
no definite areas of abundance which might be looked upon as local centers of repro- 
duction have yet been demonstrated for this species in the gulf, notwithstanding the 
large numbers of locality records and counts of actual abundance which the Grampus, 
Albatross, and Halcyon cruises have afforded. The fact that it has been found most 
regularly in the eastern and southern parts of the gulf points to a certain amount of 
immigration via the two channels and across Browns Bank from the continenta 
shelf off Nova Scotia, where the Canadian fisheries expedition found it widespread 
(Willey, 1919). 
Until its status is better understood in the gulf the latter may be looked on as a 
regular and important breeding center for it, but with the local stock augmented by 
immigration. 
Relationship to physical conditions. — In other seas M. lucens has been found over 
a wide range of temperatures from 4.83 to 20.5°, usually upwards of 5.5°; and 
in salinities ranging from 28.1 to 35.4 per mille, most commonly in 33.3 to 35.3 per 
mille (Farran, 1910; Esterly, 1912). The Gulf of Maine records bring the lower 
limit of temperature down to 0.33 to 0.78° (station 20062, March 5, 1920); and its 
presence on the surface in the coastal waters of the gulf in late winter and early 
