54 U. S. BUREAU OF FISHERIES 
cut seed-oyster producing section. ‘The methods puploved in this 
study were identical with those used the previous year 
Observations of the past 2 summers on the spawning of oysters 
in Long Island Sound indicate that, contrary to common belief, 
ee may take place at temperatures seve eral degrees lower than 
20° C. (68.5° F.). The first spawning of oysters occurred on June 
28, far in advance of the expected time and at a temperature of only 
16.4° C. (62° F.). The highest temperature recorded on this day at. 
any of our sampling stations, distributed over a distance of 30 miles 
of the oyster-producing section of the Sound, was 18.3° C. (66° F.). 
The average bottom-water temperature of all 15 stations was 17° C. 
(63°xER3): “To avoid any errors in recording the water temperature, 
measurements were taken simultaneously with four deep-sea reversing 
thermometers, their correctness was verified by the United States 
Bureau of Standards, and the temperature was read by two 
investigators. 
These observations indicate the need for modifying previous 
methods for predicting the time of spawning which have been based 
upon the assumption that oysters do not spawn at a temperature 
below 20° C. It is evident that other factors, undetermined at pres- 
ent, are involved in inducing the spawning of oysters at low tempera- 
tures. Until these factors and their role in stimulating the shedding 
of sex cells is ascertained, no infallible method for ‘predicting the 
spawning time of oysters living under natural conditions can be 
advanced. 
Throughout the summer systematic observations on the setting of 
oyster larvae were made at some 37 stations located in different sec- 
tions of the Connecticut oyster-growing area. In general the setting 
occurred late and was extremely light. During the course of these 
surveys information on the condition of oysters and the prospects 
of obtaining set was supplied to oystermen at regular intervals 
through a bulletin distributed by the Connecticut Shellfish Com: 
mission. : 
Observations on vertical distribution of oyster set in 1938 fully 
support conclusions reached during the previous year to the effect 
that in Milford Harbor setting occurs in the zone extending from 
the bottom to a point 2 or 3 feet above low-water mark. Above this 
level to high-water mark, a distance of about 4 or 5 feet, no setting 
occurs. 
Chemical control of starfish—A method for the control of starfish 
by chemical means was tested during the year in large-scale experi- 
ments in the Long Island Sound area. Early results of these field 
experiments and of previous laboratory tests indicate that important 
progress has been made toward effecting the control of the most 
important enemy of the oyster in the New England ares 
Since mechanical control of starfish on oyster beds is expensive 
and only partially effective, the advantages of employing some toxic 
substance for the eradication of these pests have been obvious. Labo- 
ratory experiments on the use of caleium oxide, or quicklime, for the 
destruction of starfish were therefore initiated at the Milford Labora- 
tory in 1937 by Dr. Loosanoff and Mr. Engle. During the spring and 
summer of 1938 the method was also tested under natural conditions 
on the oyster beds of Long Island Sound, where starfish are abundant. 
