around a potentially dangerous area. Nonswimming forms, 

 such as eggs of striped bass and shad, can be collected on 

 the screen and carried into the bypass. 



The traveling screen has other advantages. Installa- 

 tion costs are reduced because of the simplicity of design; 

 maintenance is minimized because all major operating parts 

 are out of the water and panels can be easily lifted; and 

 the screen does not appreciably alter river flow. 



Since its conception, the traveling screen has been con- 

 siderably improved. The latest prototype (Model VI), 8-5- 

 ft. long, screening over 100 second feet of water at a 6-ft. 

 depth, is being operated and tested on the Grande Ronde 

 River near Troy, Oreg. A larger, improved model in the 

 Leaburg Canal of the Eugene Water and Electric Board 

 will have a screening capacity of 2,500 second feet. 



Fish "Taxis" 



If young salmon and trout could be collected in their sea- 

 ward migration and carried around dams, many of the 

 dangers to their survival could be bypassed. But the trans- 

 portation of fish around areas through which they normally 

 migrate might decrease their ability to return as adults to 

 their home stream. Homing seems to depend partly upon 

 a learned or hereditary capacity to recognize minute chemical 

 qualities of the streams. 



Transportation experiments were made to see whether 

 survival could be increased and to learn if homing will be 

 impaired (fig. 40). Wild spring chinook salmon were trans- 

 ported from Ice Harbor Dam on the Columbia River and 

 released below John Day and Bonneville Dams. Their sur- 

 vival to the estuary was twice that of nontransported fish. 

 Survival of hatchery-reared fish may be increased even more 

 by transportation. In one experiment using fall chinook 

 salmon reared in Ringold Hatchery, the survival of fish 

 transported 160 miles around four dams was 20 times greater 

 than that of fish migrating from the hatchery. 



The transported fish were marked with magnetic wire 

 tags so they can be identified when they return as adults. 

 The magnetic tag eliminates the disadvantages of other 

 marking systems and is the best tool for the job at present. 

 The tags of stainless steel wire (4/100 inch long and 1/100 

 inch diameter) can be injected in the snouts of fingerlings 

 at the rate of 1,000 per hour. As many as six colors allows 

 a choice of thousands of combinations. After insertion, the 

 tags are magnetized. When the adults return, the tagged 

 fish will be separated from untagged fish by magnetic de- 

 tectors and separating devices in fishways. We hope that 

 enough adults will come back to give us an idea of how 

 transportation aflfects homing ability. 



FIGURE 40.-Tnick used to transport fingerlings around dams. 

 The 5,000-gallon tank truck has a refrigeration-aeration system 

 and filter. Capacity is 400,000 fish, 2'/2-inches long. 



30 — 



