224 
BULLETIN OF THE BUREAU OF FISHERIES 
and other places and planted here on hard and gravelly bottoms a few feet below 
low water. The general distribution of the beds is shown in Figure 15. According 
to local oystermen, there are only 12 acres in the bay that are considered good growing 
grounds and capable of supporting the growth of 500 bushels of oysters to each acre. 
The adult oyster population in the bay is changeable and varies depending on the 
commercial operations of the industry. Hence, it was impossible to ascertain accu- 
rately the number of oysters present at the beginning of the spawning season; it 
was estimated, however, that in July, 1928, there were at least 15,000 bushels of adult 
oysters in various sections of the bay. 
The principal business of oystermen in Onset Bay is seed production, only a 
few native oysters being grown locally, as nearly all the crops of seed oysters is 
sold the first fall, before the onset of cold weather, which would kill the spat above 
the tide lines. The area devoted to catching of spat is rather small; it comprises 
7 bars having a total area of about 8 % acres confined to the tidal land entirely 
exposed at low water. About 2,000 bushels of scallop, quahaug, or oyster shells are 
usually planted to each acre of bar. 
Onset Bay has a well-established reputation as an excellent seed-producing area, 
where setting is usually very good. On the other hand, the area utilized for the 
production of seed is very small and the possibility of extending it has great importance 
to the local industry. These facts were the main reasons for selecting the place 
for the experiments with spat collectors. 
The work in Onset was carried out during the summers of 1927 and 1928. 
Through the courtesy of the Schroeder & Besse Oyster Co., a space in the office 
building of the company was given for a temporary laboratory, and valuable assist- 
ance was rendered in supplying boats and equipment and in giving practical infor- 
mation concerning the oyster industry of the region. Under the general direction 
of P. S. Galtsoff, field observations were carried out in 1927 by Dr. E. B. Perkins 
and in 1928 by H. C. McMillin. 
TEMPERATURE OF THE WATER 
Temperature readings were taken daily at various stages of the tide at station A, 
off Shell Point (fig. 15), which was selected because Shell Point bar is the most 
important seed-producing area of the bay. On account of the shallowmess of the place, 
only surface temperature was recorded. The results of the observations made 
in July-September, 1927 and 1928, presented in Figure 16 and Tables 12 and 13 
show that except for five days in August, 1927, the temperature of the water during 
the 2-month period (July-August) was above 20° C., and that in both years the 
maximum temperature, 26.5° C. in 1927 8nd 26.1° C. in 1928, occurred in the second 
half of July. 
An attempt to obtain a continuous record of the temperature of the water was 
made in 1928 when a thermograph was installed on a float anchored in East River 
just above the bridge. (Fig. 15.) Unfortunately on July 14 the thermograph was 
lost in a gale which swept Cape Cod and produced strong waves even in a well pro- 
tected harbor. The thermograph records obtained for 13 days from June 29 until 
July 13, show that during this period the maximum fluctuation of the temperature 
within each 24-hour period was 4°. 
