

FISHERY INDUSTRIES OF THE UNITED STATES, 1938 203 
freshness. Lactic acid determinations have been made on these fish 
before storage and at regular intervals during storage. Results ob- 
tained at this point of the investigation indicate that the lactic acid 
content of sea trout muscle varies from 0.05 percent to 0.40 percent. 
Sea trout frozen while in muscular rigor show a higher lactic acid con- 
tent than those frozen under the other conditions cf relative freshness 
or decomposition. 
IDENTIFICATION OF CANNED SALMON 
Studies on the possibility of differentiating between the species of 
salmon, on the basis of the refractive index and color of the free oil in 
the canned product, were continued. A statistical analysis of the 
data obtaied during the preceding year indicated that the data at 
hand were not sufficient for satisfactory interpretation. Accordingly, 
additional samples have been taken, and sampling will be continued 
until enough data have been obtained to permit a thorough investiga- 
tion of the reliability of such a method for identifying the various 
species of salmon after canning. 
CHANGES IN THE COMPOSITION OF PINK SALMON (Oncorhynchus 
gorbuscha) 
Pacific salmon, especially the pink or humpback, are known to 
undergo considerable physical change during their spawning migra- 
tion. This change is manifest by a gradual decrease in the pigmenta- 
tion of the flesh, softening of flesh texture, and a decrease in the fat 
content of the edible portions. Generally speaking, the fish are be- 
lieved to become poorer in quality until a point is reached where 
they are considered no longer suitable for canning. Salmon, however, 
are consumed as a protein food and very little information is available 
regarding the relation of these apparent changes to the nature of the 
protein present. 
A chemical study of this problem was undertaken during the summer 
of 1937 and was continued during the past year. The actual chemical 
determinations have been completed and the data are being assembled 
and analyzed for publication. While it is considered inadvisable to 
draw definite conclusions at this time, the data, which involve analyses 
for moisture, fat, protein, ash, soluble nitrogen, heat coagulable soluble 
nitrogen, free amino nitrogen, copper precipitable nitrogen, phospho- 
tungstic acid precipitable nitrogen, and the amino acids cystine, 
tyrosine, tryptophane, and arginine, would indicate that the pro- 
nounced change in the appearance and texture of the flesh is accom- 
panied by much less change in its chemical nature. 
COMPOSITION OF COMMERCIAL SPECIES OF FISH TAKEN ON THE PACIFIC 
COAST 
The Bureau of Fisheries receives numerous inquiries from both the 
producer and consumer of fishery products regarding the composition 
of various food fish and the relative amounts of wastage involved in 
dressing. In seeking the necessary information, it is found that much 
of the data required is either not available or of a very fragmentary 
nature. Accordingly, during the past year studies were undertaken 
