484. Chemical Study of Food Fishes 
of herring has been studied by Hjort (2). It is obvious, therefore, that we 
should know the locality of the catch, the season of the year, the weight 
of the fish, and also as much of its habits at the catching time as possible, 
in order to interpret analytical results. 
Polimanti (8) has considered the relation of habitat to the fat content 
of the flesh and is of the opinion that the deep-sea fish are poor in fat 
while the surface swimming forms are rich. Aside from the relation be- 
tween habitat and the content. of fat, there is undoubtedly a close relation 
between the amount of fat stored in the edible portions of the fish and the 
processes of reproduction. This has been observed by Atwater (1), who 
gives the composition of ordinary and spent salmon. The fish on their 
way to the spawning grounds contained 13 per cent of fat, while the spent 
fish contained but 3 per cent. The work of Miescher-Ruesch (9) on the 
Rhine salmon gives a similar picture, and the later work of Paton (10) on 
Scotch salmon, and of Green (11) on Pacific coast salmon, is confirmatory. 
According to the latter two investigators, the fat stored in the body of the 
salmon during the period of feeding and growth is the immediate source 
of energy expended by the fish during spawning migration when no food is 
taken. Also, the observation by Lichtenfelt (12), who noted that during 
hunger a fat-rich fish loses a greater proportion of its fat than a fat-poor 
fish, may, when the analytical data are supplied, throw some light upon 
the habits of certain species. 
Whatever the biological significance of the changing composition may 
be, the fact remains that a large number of our food fishes have a greatly 
increased fat content in the late summer and autumn, as shown in Table 
II, compiled from: Atwater’s (1) analyses, and also by the analytical re- 
sults recorded in Table IV. 
TABLE II. 
Analyses of Food Fish by Atwater, Arranged to Show Seasonal Variation. 
Fresh Basis. 
Fish. 
Water. Solids. Fat. Ash. Nitrogen. 
Name. When caught. 
per cent per cent per cent per cent per cent 
Blackfish. | Mar., 1882 | 81.36 18.64 0.55 0.65 2.82 
a Apr., 1882 | 79.64 20.36 0.62 1.03 3.03 
“ May, 1882 | 78.44 | 21.56 1.44 1.36 3.038 
Mackerel. | May, 1880 | 74.14 25.86 6.99 1.30 2.91 
te Dec., 1880 | 64.01 35.99 16.30 1.48 3.05 
The results of Atwater’s investigations have been accepted as repre- 
senting the correct composition of American food fishes. The dietitian, 
in calculating the fuel value of the food components present in different 
species of fish, has used these figures. They have been quoted by a num- 
ber of writers. 
