98 University of California Publications in Zoology [ Vou. 14 
SUMMARY 
1. This report discusses the methods employed in the course of a 
biological survey of San Francisco Bay, conducted by the United 
States Fisheries Steamer “‘ Albatross’’ during the years 1912 and 1913, 
together with the principal data derived from the hydrographic 
observations which were made. 
2. The latter were for the most part conducted during six obser- 
vation periods, at approximately bimonthly intervals, throughout the 
course of one year. To this regular series must be added considerable 
supplementary work, carried on during the following year. 
3. The physical factors of the environment to which attention was 
chiefly devoted were depth, velocity of current, temperature, salinity 
and character of bottom. Various caleulations have likewise been 
made, based upon the published records of the United States Coast 
and Geodetic Survey and other sources. 
4. The mean depth of San Francisco Bay (computed from charted 
soundings) is 22.7 feet (6.9 meters). Leaving out of account the 
Golden Gate, the greatest depth in the bay is 36 fathoms (66 meters). 
Throughout more than eighty per cent of its area, the depth is less 
than five fathoms (nine meters). 
5. The volume of water, at mean low tide, has been estimated as 
5,015,600 acre-feet (6,187,000,000 cubic meters). The amount of 
water present at mean high tide is greater than this by 1,077,600 aecre- 
feet. Thus, about 17.7 per cent of the water present at high tide 
passes out during the average ebb. 
6. The mean rate of the tidal currents, based upon 142 surface 
observations, made at all phases of the tide, throughout the navigable 
parts of the bay, was found to be about 1.4 knots (nautical miles) per 
hour. The average figure for the ebb current readings was 1.68 knots, 
the average for the flood readings being 1.19 knots. The maximum 
figure recorded during our observations was 3.03 knots, though much 
swifter currents are known to occur in the Golden Gate. 
7. The mean tidal range, at nine points distributed at fairly equal 
intervals throughout the bay (based upon Coast Survey figures) is 
4.52 feet (1.38 meters). 
8. The mean temperature of the entire bay, during the year 
covered by our observations, was 12°91 C (55°23 F). The regional 
means ranged from 12°01 C, the annual mean for a station near the 
