ARTIFICIAL PROPAGATION OF PACIFIC SALMONS. 17 



the ordinary pound net. In their eager efforts to pass upstream 

 the fish go "through the V-shaped mouth of the ttap, and, having 

 once entered, they seldom find their way out. The trap is usually 

 covered to prevent the escape of the fish by jumping. 



In streams where the current is strong, as in Oregon and Wash- 

 ington, the fish are sometimes taken on the riffles by means of gill 

 nets; but, as many are killed or injured when so caught, this method 

 should be employed only as a last resort. 



In the comparatively slow streams of California it is customary 

 to employ drag or sweep seines of suitable length and depth, which 

 are operated below the head rack and above the retaining rack. 



Where the natural conditions will permit, the most economical 

 means of capturing salmon is by the use of a downstream trap. The 

 use of this device necessitates that the upper rack be placed across 

 the river at the head of a spawning riffle having a good fall. The 

 wings of the trap, constructed on the same principle as the rack and 

 with openings provided near the shore ends for the entrance of the 

 salmon to the spawning waters below the main rack, are run down- 

 stream from one or both shores, as local conditions may require, and 

 at their convergence the trap is located. The trap, which is usually 

 about 5 feet wide, is made of smoothly dressed slats or poles, the 

 small ends of which are nailed to a light sill sunk in the bed of the 

 stream, with a space of 1^ inches between each pole, to allow the 

 water to flow through freely. From the sill they rise in a gentle 

 incline downstream to a level a few inches above the point where 

 the water runs through, and they are then sprung down and nailed 

 to sills, forming the bottom of the trap. The sides of the entrance 

 and the trap proper are usually made of poles or pickets placed 

 horizontally, with sufficient space between to permit water to escape 

 freely. The sides of the entrance are well braced to withstand the 

 pounding of the salmon when rushing into the trap in numbers, and 

 on either side of the trap live pens for holding the ripe fish are 

 constructed. Across its entrance a grating is placed to prevent the 

 fish from being carried into it when not in use. 



When the trap is to be fished, the openings in the lead are closed 

 and the grating at the entrance removed. The seine is laid out at the 

 head of the riffle, whence it is rapidly carried by the current down- 

 stream toward the trap. The fish on the riffle become frightened at 

 the seine and run downstream. Following the converging leads and 

 traveling rapidly with the current, they are driven into the mouth 

 of the trap. Before they can turn, their momentum carries them 

 high and dry onto the trap floor, where an attendant picks them up, 

 liberates the green fish in the water below, and places the ripe males 

 and females in their respective pens. The fish which try to turn 

 back before reaching the trap are caught by the heavy leaded seine 

 and held against the lead racks until the fishermen find them. 



At the Big White Salmon station of the Bureau of Fisheries suc- 

 cess has been attained by purchasing salmon from the fish-trap men 

 and towing them in live cars to an inclosure made by racking a 

 spring creek having a soft, sandy bottom, which is particularly 

 adapted to the successful ripening of immature fish. The death rate 

 of the fish while being held there to ripen is small, and the eggs 

 taken from them are of excellent quality. 



