298 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
tlie local market. The one element of food which has inost generally been found to 
till these conditions is lis er. It was iwobably the most fortunate accident in the 
history of tish culture that the circumstances of the first three conditions forced the 
attention of the early culturists to liver. Its adoption may be viewed in the light of 
a lucky accident, for in those days oidy the first tlii'ee conditions were recognized, and 
the fourth and most important condition, the proper combination of the elements 
with a view to the requirements, was not considered by the fish-culturist. To-day, 
unfortunately, it is but slightly understood. In substantiation of the view of the 
value of liver the reader is referred to Prof. E. Wolff’s table of percentage of nutritive 
substances used as fish food.* From this table it appears that the chemical compo- 
sition of liver (and hearts, lungs, and brains of oxen) more nearly approximates that 
of insects and their larvm tlmu does any other article of animal substance which has 
j’et come into use. 
In ISTicklas’s Pond Culture the studj^ otWhe food for carp is detailed fully. ISTick- 
las deduces the formula that — 
The most favorable proportion of nutritive substances in car]i food is Nh : Nfr ; : 1 : 0.5 (or 0.6), 
and that consequently food containing a good deal of nitrogen is the best and most profitable for caiq). 
The most suitable articles for food, therefore, are blood, horseflesh, Ihsli guano, curds, meat dried and 
ground fine, refuse from slaughterhouses, etc. All these, however, require to ho mixed with other articles 
of food containing less nitrogen, so as to restore the qjroqjer iiroporiion of nntrilire substances. On the whole 
the food I'or the carp will have to be mixed very much on the same principle as that for cattle and 
other domestic animals. 
The italics in this quotation are mine. When it is remembered that Nicklas’s 
formula was evolved to apiily to the sluggish and slow-breathing carp, and that the 
main subject of this paiier is the active and rapid-breathing trout, the emphasis will 
be apparent. The very largest proportion of the nonnitrogenous elements of food 
required by the trout (and it will be very much in excess of that needed by the carp) 
is for the purpose of I'espiration. It is for this reason that the otherwise excellent 
article of liver, when employed alone, has not proven a x>crfect food for trout; and it is 
partly from this reason that the Neosho method of mixing a large proportion of uou- 
nitrogenous substance with tlie liver has secured such satisfactory results. 
If the careless reader is inclined to ask, Why is not a food well adapted to one 
kind of fish (carp) equally \vell suited to another (trout)'? I would remind him that 
whereas man in the tropics needs but the scantiest quantity of fats and oils the 
Eskimo requires 20 pounds of animal food daily.! It would be a serious error to 
suppose that the food suited to carp is eqirally suited to trout, or that the food 
adapted to trout living in a mean temperature of 55° to 05° would be the best for the 
same fish in a mean temperature 30° lower. The very change in the rate of respira- 
tion consequent on the change of temperature would, if the feeding was to be done on 
the most economical and rational basis, entail a change in the character of the food. 
A consideration of these facts led me some years ago to adopt a mode of feeding trout 
which has since become known as the “Neosho method.” The following description 
of the method of preparing the food and feeding the fish at the Neosho station may 
be of interest. 
*Die Teichwirthschaft. From tfie Lehrbach der Teicliwirtlischaft, by Carl Nickla.s. Uuited 
States Fish Commission Eeport, 1881, p. 167. Translated from the German by Herman .Jacobson. 
t Second Voyage for the Discovery of the Northwest Passage (Sir John Eoss). 
