296 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
The difference in locality, elevation above the sea, and mean annual temperature 
of the water at tlie hatcheries is quite varied, but not more so than the daily rations 
given. As for the results — the weight of the yearling fish — the data as given do not 
admit of a too close comparison, some of the fish having been weighed at 10 months 
old and others at 15 months old. 
H owever, a study of the table does show that tliere is not only a decided lack of 
harmony between the practice or methods of feeding followed at the various estab- 
lishments, but that some are giving an inadequate quantity of food and others are 
feeding far in excess of the needs. For instance : Leadville Station gives but 2 ounces 
of animal food per day per 1,000 yearling trout, while the Willow Brook Hatchery, 
of the Minnesota Fish Commission, gives eighty times as much to the same number of 
fish. The quantity of food used at the Leadville Station is the smallest for which I 
have any return, and it is not surprising to find that the fisli grown there are smaller 
than at any other hatchery in the United States. The next smallest is the Howie- 
toun Fishery, of Scotland, where the ration is but two-thirds of a pound and the 
weight of 1,000 yearling fish (Loch Leven trout) but 10 pounds. 
When the very small size of the fish produced at Leadville first came under my 
notice I was of the opinion that the extreme altitude of the place might in some way 
(possibly by reason of the low temperature of the water consequent npiou such great 
elevation) be a controlling factor in producing such a slow growth. So firmly was 
this idea fixed, that when the returns from the Mexican hatcheries were received I 
requested a retesting of the weights. Not only was the weight as first given corrobo- 
rated, but a sample of the food used was furnished. In that sample of food, “^mos- 
quitte” {Coriza femorata) was found the secret. It was a correct food, unfortunately 
at present beyond the reach of American fish-culturists. 
Seeing, then, that the laws of the text-books and the general practice are so 
variable, vague, and unsatisfactory, let us see what may be determined by analogous 
reasoning from the established laws of dietetics for other animals. 
Before entering upon this branch of the subject the reader is requested to bear 
in mind that fish are cold-blooded and will never need— in fact, would be overburdened 
with — as large a proportion of heat-producing foods as are needed by the warm-blooded 
animals. Being cold-blooded, they have no body temperature to maintain, and so do 
not require in so large a degree the rich hydrates of carbon needed by the warm- 
blooded animals. Again, in small ponds, where the very largest per cent of the food 
is supplied artificially, the work of the fishes in procuring a livelihood is reduced 
to a minimum, and this will also be found a factor in determining the character of the 
food to be supplied. 
Animals for which laws of dietetics have been established most nearly resembling 
the condition of fishes under domestication are cattle and men not at Avork. But no 
perTect parallel can be drawn between these classes on account of the body heat to be 
maintained on the one hand and its absence on the other. It seems that the average 
man, passive or at lighte.st work, requires, according to the Amrious authorities, solid 
substances ranging from 20 to 41 ounces per day.* Assuming the average man to 
weigh 130 pounds, the aimrage of the alloAcance of the authorities would be 1^ per 
cent of the Aveight of the man. I)r. M. G-. Ellzey, formerly professor of agriculture at 
* Billings’s National Medical Dictionary, p. xxxix; Flint’s Text-Book Human Physiology, pp. 191, 
192; Marshall’s Outlines Physiology, p. 899. 
