THE
POPULAR SCIENCE
MONTHLY
JULY, 1902.
| STUDIES IN THE NATURAL HISTORY OF THE SACRAMENTO SALMON. |
BY CLOUDSLEY RUTTER.
ASSISTANT, U. S. FISH COMMISSION.
THE following notes are derived mainly from a series of investigations carried on under the direction of the U. S. Commissioner of Fish and Fisheries, by whose permission they are here used.
The Pacific salmons, the genus Oncorhynchus, of which there are five species, are very distinct from the Atlantic salmon of the genus Salmo. In fact, they have no more right to the name salmon than wolves have to the name fox. Anatomically the two genera do not differ greatly—Oncorhynchus having 14 or more rays in the anal fin, and Salmo 10 to 12—but physiologically and in life-history they differ in a marked degree.
The most important difference lies in the fact that the Pacific salmon, of whatever species, dies immediately after spawning once. This is true of both males and females, and is a very remarkable characteristic. It is often denied upon a priori reasoning, the common argument being that, if they all died on the spawning beds the rivers would be full of dead salmon floating down stream. But the common idea that dead fishes float is erroneous. Those that die a natural death do not float, and the salmon is not an exception.
Natural Propagation.
Under natural conditions, the female salmon extrudes the ova, a few at a time, in a swift current near the bottom of the stream. Many are carried several feet, or even yards, down stream by the current, and are nearly always devoured by other fishes, such as the trout, sculpin,
