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BULLETIN OF THE BUREAU OF FISHERIES 
wherever oyster beds existed, the number of perforated shells among a definite 
number of oysters taken at random. The study was made in June, 1927, so as to 
avoid the low salinities which obtain during the spring months. (See salinity chart, 
fig. 3.) In order to ascertain the relative number of drills over the various beds a 
small oyster dredge was dragged over the bottom for 5 minutes behind a slow moving 
motor boat. The following table shows the results of the survey: 
