134 
BULLETIN OF THE BUREAU OF FISHERIES. 
dispatch was used to prevent asphyxiation and care taken to avoid injury during the 
necessary handling. 
MARKING TAGS AND TOOLS. 
The tags used to mark the salmon in this experiment were made of aluminum and 
were extremely light and very strong. The entire tag or button weighed 2.6 grams 
ounce). The tag was made of two pieces on the general principle of a Yankee 
button (fig. 1). The piece B consisted of a circular disk, 1 mm. thick by 19 mm. in 
diameter, which was forged to a hollow shaft, 7 mm. long by 7 mm. in diameter. The 
shaft had a hole through its length some 4 mm. in diameter. A serial number was 
stamped on the face of the disk (fig. 1, D). Piece A was a disk similar to B but forged 
to a solid rivet, 4 mm. in diameter by 9 mm. long. On this face was stamped the words 
“U. S. Fish,” as shown in E. When the rivet of piece A is inserted into the shaft of 
B (fig. 1, C), the rivet projects 2 mm., which gives ample length for securing. When 
the two pieces are adjusted and the rivet compressed, the soft aluminum fills the shaft 
and the end is mashed down so that the two pieces can not be torn apart (fig. 1, D). 
The marking pliers (fig. 2) used in this experiment were supplied by the manu- 
facturer of the marking buttons. They were of cast iron, quite large, and rather heavy 
for quick work. The pliers were 28 centimeters long and weighed 670 grams. Between 
the handles there was inserted a hollow punch that cut a hole 7 mm. in diameter. The 
width of the pliers was adjustable to the length of the button, the adjustment being made 
by threading in one jaw. It was not necessary to use this adjusting device in the salmon 
experiments, since the thickness of the salmon fin was never so great but that the pieces 
of the button could be completely thrust home with the fingers without the aid of the 
pliers. 
CONDITIONS AND DETAILS OF MARKING PROCESS. 
When a salmon is caught up in a dip net he struggles vigorously to get away. One 
should use a relatively large dip net with a wide flat bottom (i. e., not the usual round or 
kettle-shaped bottom). With such a net it is very easy to manage a fish through the 
struggling stage so that it does no injury to itself. It is not necessary that scales should 
be lost, even in such loose-scaled fish as the silver salmon. 
In this experiment when a fish was caught it was held with the bottom of the net 
just deep enough in the water for the fish to struggle against the resistance of the water. 
While this method resulted in a goodly quantity of water being thrown over the operator, 
it had the very desirable effect of quickly producing a temporary fatigue of the salmon. 
As a result of this fatigue, the fish remained quiet for a number of seconds. 
The instant a fish stopped struggling it was lifted out of the water, seized by the tail 
with a strong grip of the hand, swung free of the net, and over the free arm of the oper- 
ator. The next instant it was quickly but gently laid out on the measuring platform 
and its length read off. The measuring platform consisted of a broad board with an 
upright at one end. A meter stick was tacked to the board with its zero against the 
upright. Loose folds of burlap were laid over the board and over the meter stick for 
