OYSTER KESOURCES OF THE PACIFIC COAST. 345 



Tempcr'aturc. — The popular belief that tlie low temperature of the water 

 of San Francisco Bay lias i)revented 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 lias, 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. I>. Moraghau, an oyster-dealer of San Francisco, says that 

 the temperature at his oyster beds at Millbrae ranges from 58° to 05° F. 

 At the extreme southern end of the bay the summer temperature has 

 recently been found to be much higher, ranging from 07° to 74° F. for 

 July and August. My personal observations on the temperature were 

 of course limited to times when tlie Albatross happened to be in port, 

 and as this never occurred 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 

 Califorina 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 oj^ster indicate that 

 the nearer tlie temperature to 70° the more likely is success. During 

 thelatterpart of October, 1890, 1 found the temperature of the southern 

 part of the bay, near Belmont, to be usually 01° F. On the same dates, 

 in the region of San Mateo, a few miles nearer the sea, it was 1° lower; 

 Avhile at California City, still nearer, it was 57°. Recent observations 

 have shown, however, that the water temj)erature is much lower in 

 October than in the midsummer season. It is 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 

 California. 



