PRODUCTION AND COLLECTION OF SEED OYSTERS 
249 
In the studies of the physical conditions in Milford Harbor during the periods when 
larval development was in progress, it has been found that extreme changes in water 
temperature, ranging from 5° C. to 11.5° C. in 24 hours, or in salinity from 5 to 25 
per mille, produced no noticeable decrease in the numbers of larvae present in the 
water. During the larval period in 1925 and in 1927, the precipitation was several 
inches above normal and there was a great amount of fresh water discharged 
into Milford Harbor. The changes in salinity and the increased velocity of the ebb 
current following these storms did not kill the larvae or carry them out of the harbor. 
The studies at Milford show that the oyster larvae can withstand wide changes in 
the temperature and salinity of the water and are not carried away by the tides and 
currents. 
SETTING 
The successful collection of oyster seed in any particular region or body of water 
is dependent upon a knowledge of when setting will occur, where it will be most 
intensive in relation to the spawning bed or depth of water, and how great the pTo- 
duction of spat is likely to be during that season. 
In the studies as to the time and distribution of setting in Milford Harbor, 
various types of spat collectors were used such as tiles, brush, tar paper, and con- 
tainers filled with oyster, clam, scallop, and mussel, shells. The collectors were 
arranged so as to cover the entire zone from the bottom of the channel to high-water 
mark — a vertical distance of approximately 17 feet, of which the upper 5 to 9 feet 
are exposed by the tides. 
Setting in Milford Harbor has been observed to occur from July 20 to September 
1 but is generally most intensive during August with the peak occurring about the 
middle of the month. The first early set is extremely light and is followed by a 
heavy and final set about 8 or 10 days later. For example, in 1925 there were 10 to 
15 spat per shell at station No. 3 from the light set on July 20 and from 150 to 250 
spat per shell from the heavy set on July 29. The daily examination of the shells 
showed that the setting period of the majority of the larvae of a single spawning 
lasted but two days. In 1926 the heavy set occurred on August 16, which is repre- 
sentative of the average time of setting for this region. 
The number of spat produced in the harbor each year varied considerably though 
the number of spawners was practically the same in each instance. It was found 
that the intensity of setting could be clearly correlated with the quantity of spawn 
in the oysters and the early water temperatures. In 1925 when the temperature 
was above normal and the oysters contained a large amount of spawn, the setting 
was heaviest, and an average of 15,000 spat were collected per bushel of shells. In 
1926 and 1927 we had the other extreme — that is, water temperatures below normal 
and small amount of spawn in each oyster — with the result that the average number 
of spat collected per bushel was only 2,000 and 2,500 respectively. Such annual 
variations in the production of seed on both natural and cultivated oyster beds have 
long been observed and is largely the result of the fluctuations in the physical con- 
dition of the water which have been discussed previously. 
The intensity of setting according to depth or in other words the vertical dis- 
tribution of spat is quite peculiar in Connecticut waters. In Milford Harbor the 
spat were found to be attached in a zone extending from the bottom of the channel 
to a point 2 feet above mean low-water mark; while from above this level to high- 
water mark, a distance of about 5 feet, no setting takes place. In other bodies of 
