586 
CHARLES WILSON GREENE 
A DISCUSSION OF THE RESULTS OF THE MARKING EXPERIMENT 
Three species of salmon are represented in the experiment. 
There were 25 Chinooks (Oncorhynchiis tschawytscha), 16 
silver salmon (O. kisutch), and 18 steelhead (Salmo gairdneri), 
59 fish in all. These fish ranged in length from 41 cm. to 103 cm., 
and in weight up to thirty-five pounds, and were well distributed 
in size. Out of the total number liberated, 17 were reported 
caught again, and the marking buttons of 16 of these were re- 
covered. Six of the recovered fishes were Chinooks, 6 silvers, 
and 5 steelhead. The general facts of the experiment are assem- 
bled in table 1. 
The aluminum metal of the . marking buttons proved to be of 
special value in an unexpected way. Aluminum is strongly cor- 
roded in salt water, and not affected in fresh water. This serves to 
give an index on the career of the fish in salt and brackish water. 
The strong corrosion which appeared on some of the marking 
buttons is positive proof of the return of the fish to salt water 
after they were marked. The degree of corrosion cannot be 
taken as an estimate of the relative time spent in concentrated 
as against relatively dilute sea-water. In other words a given 
corrosion may mean a long sojourn in slightly brackish water, 
or a shorter sojourn in relatively pure sea-water. But in certain 
specimens, as for example number 80 which was out only eleven 
days until caught again, it is safe to assume that the fish spent 
most of the time in relatively undiluted sea-water. 
Two of the Chinook salmon, numbers 80 and 123, were re-taken 
after eleven and thirty-one days respectively. Number 80 was 
taken fifteen miles up the river from the point liberated, a dis- 
tance requiring not over two days' time for a straight run. This 
fish had at least nine days in which its movements are unaccounted 
for. The history of the nine days is represented in the extensive 
corrosion on one face of the aluminum button. This will be read- 
ily seen from the photographs represented in figs. 1, 2. So great 
a corrosion in so short a time indicates a relatively concentrated 
sea-water. In all probability this fish swam towards the ocean 
well out toward or beyond the jetty, and the average of its time 
