558 
BULLETIN OF THE BUREAU OF FISHERIES 
May temperatures. In 1925, for instance, the surface temperature at a line of sta- 
tions from Cape Ann to Cape Cod rose from 4.3° to 4.4° on April 21 to 23 to 8.3° 
to 9.4° on May 20 to 22 ( Fish Hawk cruise 13); and vernal warming proceeded 
at about this same rate there in 1920, when the surface reading rose from 2.5° off 
Gloucester on March 1 (station 20050) and 3.3° on April 9 (station 20090) to 6.39° 
on May 4 (station 20120) and 9.72° on May 16 (station 20124). 
This thermal change is accompanied by an alteration in the regional distribution 
of surface temperature over the bay. Cape Cod Bay continues to be its warmest 
center, the immediate vicinity of its northern coast line its coldest, reflecting local 
stirring by the tide or some upwelling, as is the case in April (fig. 22). In 1925, 
however, the summer state was foreshadowed, as early as the last week in May, by 
slightly higher surface readings (9°) at the outer stations than between Stellwagen 
Bank and the shore (fig. 28). 
The surface of Ipswich Bay, just north of Cape Ann, warms as rapidly from 
April through May as does Massachusetts Bay, judging from readings of 3.05° on 
April 9, 1920 (station 20092) and 7.22° on May 7 and 8 (station 20122). 
Similarly, the surface temperature of the basin abreast of northern Cape Cod rose 
from 3.61° on April 19 (station 20116) to 9.17° on May 16 (station 20125); the sur- 
face of Gloucester and Boothbay Harbors rose from about 4° to about 9° between 
April 15 and May 15, and Lubec Channel from about 2° to about 5° during this same 
interval (figs. 29 to 31). As Doctor McMurrich 18 records arise from about— 1.67° 
at St. Andrews, on March 3, to about 5° to 6° in mid-May after the very cold and 
snowy winter of 1916, when the water was about 1° colder there than it was in 1917 
(Willey, 1921) or than it is likely to be again for some years to come, the surface 
may be expected to warm by about 5° to 6° between the middle of April and 
the middle of May all along the western and northern shores of the gulf and out over 
the southwestern part of the basin generally. This warming, however, is made 
irregular, no doubt, or even intermittent, by local fluctuations in the weather (e. g., 
belated snowstorms) and by the cold freshets from the rivers. 
The rise in surface temperature proceeds somewhat less rapidly out across 
Georges Bank, on the southwestern side of which we found the surface only about 3° 
warmer on May 17, 1920 (stations 20128 and 20129), than it had been there on 
February 22 (stations 20045 and 20046). Vernal warming is also less and less rapid 
from west to east across the gulf (fig. 32), with readings only fractionally higher along 
the coast of Maine east of Mount Desert Island on May 10 and 11, 1915, than on 
April 12, 1920, or between Grand Manan and Nova Scotia in 1917. 17 
Whether the surface stratum is warmer or colder in May than in April, from 
southern Nova Scotia out across German Bank (where the Nova Scotian current 
from the eastward exerts its chief effect), depends on the date when this current 
reaches its maximum and slackens again, events that certainly fall several weeks 
earlier in some years than in others. In 1919, as noted above (p. 553), icy water from 
this source was pouring into the gulf as early as the last week of March in volume 
sufficient to chill the surface to 0° as far west as the eastern side of the basin; but 
> 8 Plankton lists (p. 513). 
1 7 Mavor (1923, p. 375) records the surface at Prince station 3 as 2.27° on Apr. 9, 1917, and 2.96° on May 4. 
