BULLETIN OF THE UNITED STATES FISH COMMISSION. 205 
The water, from 2 to 3 feet in depth, being left undisturbed two or three 
weeks, is found peopled with swarming myriads of minute organisms 
of the species above named. Twenty thousand trout a year old, or 
3,000 two years old — which last should average about one-half pouud 
in weight — are considered sufficient for a pasture of that size, and the 
avidity with which they rush to occupy and ravage their new feeding- 
ground is a delight to the pisciculturist. If the propagation has been 
ordinarily abundant these 20,000 young fry or 3,000 yearlings will subsist 
royally in a tank of the size indicated for an entire month. They will 
eat on an average 20 to 25 pounds of food per day, or 600 to 800 pounds 
per month. Careful experiment has demonstrated that each tank at 
Gremaz will produce 650 to 900 pounds of Grevettes (fresh water shrimp), 
to say nothing of the myriads of Daphnia , Cyclops , and other species 
produced in the same water during the same time. When, at the close 
of the month, the tank has become depleted, the gate is opened and the 
fish driven like a flock of sheep to a new and similar pasture. The 
first tank, being closed and left in quiet, immediately begins the proc- 
ess of reproduction, and at the end of two or three weeks is swarm- 
ing again with the varied minute organic life which far surpasses in 
value, as food for fish, anything that has been yet devised by man. 
Thus the simple, inexpensive process goes on from year to year, the fish 
always healthy and vigorous and larger at two years old than those 
artificially fed are at the age of three years. Yearlings bred in this way 
are strong, and capable of making their way in any open stream or pond 
supplied with food and suitable for their existence. One thousand of 
such yearlings have been found more effective in stocking a depleted 
trout stream than fifty thousand young fry turned in, as has been so 
often done heretofore, in order to get rid of them at the tender age when 
artificial feeding first becomes not only necessary but difficult and 
troublesome. For these tender nurslings all open waters, particularly 
when inhabited by older trout or other voracious species, are beset with 
a thousand dangers which the vigorous yearling is able to escape. 
It is evident from all this that the system practiced at Gremaz is 
equally applicable to the industrial raising of trout and other fish for mar- 
ket, and to the restocking of streams and ponds for purposes of sport. In 
the first case, it is only necessary to provide a series of tanks or small 
ponds from one to another of which the fish can be changed monthly, 
as hereinbefore described, until they reach a marketable size; and it is 
to be remarked that trout raised by this method have the natural firm- 
ness and flavor of wild fish, and not the flabby, degenerate character 
of those which have been fed on liver, offal, and other unnatural, de- 
grading food. Once prepared, a tank or pond is permanently produc- 
tive. However voracious the young fish may be, they leave the bottom 
of the water still peopled with myriads of parent organisms which re- 
produce so rapidly that, before the end of a month, the placid water 
