OYSTER RESOURCES OF THE PACIFIC COAST. 345 
Temperature.—The popular belief that the low temperature of the water 
of San Francisco Bay has prevented the increase of the oyster is not 
based on any exact information on the subject. The temperature of the 
bay in the vicinity of the city of San Francisco, usually not much higher 
in summer than in winter, was early assumed to be too low for oyster 
propagation; and, from the lack of special evidence of oyster increase, 
this gradually became the common explanation to casual inquirers about 
the matter, no one making any attempt to disprove it, although the 
spat from imported oysters has, it seems, been developing and growing 
in secluded places, doubtless from the very start. The oyster-growers 
apparently keep no record of temperatures, or of other observations 
that would throw light upon the physical conditions of the bay during 
the different seasons of the year. 
Mr. M. B. Moraghan, an oyster-dealer of San Francisco, says that 
the temperature at his oyster beds at Millbrae ranges from 58° to 65° F. 
At the extreme southern end of the bay the summer temperature has 
recently been found to be much higher, ranging from 67° to 74° F. for 
July and August. My personal observations on the temperature were 
of course limited to times when the Albatross happened to be in port, 
and as this never oceurred in summer the most important season is as 
yet but little understood. The importance of studying this subject is 
evident when the influence of the marked rainy and dry seasons of 
California upon the waters of the bay is considered. Although the 
water never reaches the summer warmth of corresponding latitudes on 
the Atlantic coast, the temperature is more equable than that of most 
places upon the Atlantic coast where oysters grow, and the extremes 
of temperature are within those of such regions. It may be that the 
temperature during the spawning season of the oyster, which is of 
course the critical period, is low enough to seriously limit the quantity 
of spat developed, but this can readily be determined by a careful 
study of the beds at the proper season, which has not yet been done. 
Experiments in the artificial propagation of the oyster indicate that 
the nearer the temperature to 70° the more likely is success. During 
the latter part of October, 1890, [found the temperature of the southern 
part of the bay, near Belmont, to be usually 61° F. On the same dates, 
in the region of San Mateo, a few miles nearer the sea, it was 1° lower; 
while at California City, still nearer, it was 57°. Recent observations 
have shown, however, that the water temperature is much lower in 
October than in the midsummer season. Itis altogether probable that 
the extreme southern portions of the bay, 20 or 30 miles back from the 
Sea, are several degrees warmer at all seasons than those farther north, 
since the region is more sheltered from sea winds and the strong 
breezes of San Francisco are less noticeable there. The French system 
of claires would furnish still warmer water than any of the bays of 
Caiifornia. f 
