172 American Fisheries Society 



FISH LED IN AND ENTRAPPED. 



The entrance to the fish-compartment or fish-trap is wide, and 

 as the whole structure is a light frame work, there is no shadow or 

 darkness about it, and the fish are not deterred on that account. 

 It has been found that many kinds of fish object to entering a 

 dark hole or chamber, but in this case there is no more difficulty in 

 inducing the fish to enter the fish-compartment than in entering 

 any automatic fish-trap along the sea-shore or along the banks of 

 rivers. In order to compel the fish to enter the fish-trap, a wall of 

 wire netting or "a lead" is suspended across the river diagonally 

 which prevents the fish from ascending as far as the foot of the 

 falls or dam and forces them to lead or be guided along the wall 

 of net and enter the fish-trap, as in the case of ordinary commercial 

 fish-traps. 



HEIGHT, OPERATION INTERVALS, ETC., CAN BE VARIED. 



The height of this structure can be varied for every different 

 condition, and as it works automatically by gravitation, or 

 if necessary, by electric or other power, it will operate as success- 

 fully for a low dam, 10 feet high, as for an obstruction, 30 or 40 

 feet in height ; in other words, it is independent of the height of the 

 obstruction. By the arrangement of special valves the counter- 

 poise can be filled at the top of the elevator, and emptied at the 

 bottom of the elevator, at any desired interval of time. In some 

 cases it is desirable that the fish should be lifted up at intervals 

 of not less than two or three hours, in other cases, where great schools 

 of fish are ascending, it should ascend and carry the fish up every 

 15 or 30 minutes. This can be easily arranged by adjusting the 

 valves. 



OTHER FISH EXCLUDED WHEN TRAP ASCENDS. 



When the fish-trap has ascended, the vacant space, which 

 it occupied at the bottom, would be a danger to the fish trying 

 to enter during the interval. To shut off the entrance of fish 

 when the fish-compartment is ascending or descending, a 

 special door has been devised which drops down and keeps the 

 fish out, so that they are compelled to wait until the emptied 

 compartment completes its descent. Then, by a special device, 



