NATIONAL FISHERY CONGRESS. 
277 
exposure to a density of less than 1.005 or more than 1.022, if not fatal to the individ- 
uals, is at least fatal to the species, as young are not produced to take the place of the 
old ones which are dying off. 
In many places where the salinity is favorable during a large part of the year it 
happens that at certain seasons a heavy influx of fresh water produces a temporary 
reduction below the desired minimum. This appears to be particularly liable to occur 
on the Gulf coast, where many great streams and innumerable small ones become 
swollen by the rains and discharge large quantities of fresh water close to the oyster- 
beds. Two facts, however, tend to mitigate the evil which might result. In the first 
place the oyster is able to tightly close its shell when subjected to objectionable 
conditions, and thereby the fresh water may be for a time excluded, anti Professor 
Washburn has recently shown that they will live for upward of ten days in the water 
of running brooks. Then, too, the fresh water, being lighter than the salt or brackish, 
tends to spread over the surface of the bays into which it is discharged, and it is 
usually found that the bottom density is greater than the surface density, even after 
long-continued freshets. The changes are therefore more gradual and less radical 
than if the salt water were driven, out before the fresh, and the oyster finds conditions 
more favorable at bottom than it would be subjected to if it were a surface-dwelling 
organism. In selecting planting grounds the question of liability to the influence of 
freshets should always be given consideration, as disaster may result from its neglect. 
TEMPERATURE OF THE WATER. 
Adult oysters are not ordinarily adversely affected by temperatures ranging 
between the freezing point and 90° F. Those upon flats exposed at low water are 
olten frozen during the winter and subjected to the high temperatures of the direct 
rays of the summer sun, and yet many of them live to a ripe old age measured by the 
span of an oyster’s life. During the spawning season, however, a temperature too low 
or too high, or changes too sudden and too violent, will either kill the spat or prevent 
spawning altogether. In the Long Island and Chesapeake regions cold rains and 
periods of low thermometer are not infrequent in summer, and multitudes of oysters 
iu their swimming stage end their career in sudden adversity. On the Gulf coast 
such fatalities are of less frequent occurrence, and the probabilities of obtaining a 
set, other things being equal, is correspondingly enhanced. 
CHARACTER OF THE BOTTOM. 
To be suitable for oyster-culture the bottom should be of such consistency as will 
prevent the oysters becoming engulfed iu the mud or covered by shifting sands or 
ooze. The several surveys that have beeu made of the Gulf coast by the Fish 
Commission indicate that suitable bottom, unoccupied by a natural growth of oysters, 
may be found with but little eflort. These sections of our coast, however, appear to 
be rather more liable than the northern oyster-grounds to shiftiugs of the bottom by 
stormy seas, and the prospective oyster- grower should not be misled by deceptive 
appearances, as a loose sand in shallow water exposed to heavy or even moderate 
wave action may in a short time change its location in a manner disastrous to the 
planter. With large areas of suitable bottom open to occupation, it is not necessary 
to point out to the Gulf coast oyster-grower the means by which his Connecticut 
brother has made available to his purposes many thousand acres of bottom by nature 
wholly unadapted to the oyster. 
