Figure 9. — An experimental tank, located 

 along one of the walkways, equipped to 

 evaluate small tunnels to be used in 

 passing downstream migrating finger lings. 

 Infrared lamp hanging above tank. 



Studies of underwater sound and fish 

 behavior use underwater sound transducers 

 and hydrophones developed for this purpose. 

 A more detailed description of this equip- 

 ment and its past use are given by Moore 

 and Newman (1956). 



Studies in small tanks requiring regu- 

 lated water flows can be supplied by 2-inch 

 hose from a high-velocity pump discharging 

 up to 400 gallons per minute. This pump is 

 on the machinery deck and pumps from the 

 sump below. 



Most of these studies demand precise 

 measurements of environmental conditions 

 such as water velocities, light intensi- 

 ties, and electric potentials. These are 

 measured by appropriate standard instruments 

 such as water current meters, light meters, 

 oscilloscopes, and vacuum-tube voltmeters. 



Fish-holding facilities 



The tests performed in the Behavior 

 Laboratory, because of their number and 

 variety, require several tanks for holding 

 fish in small lots separately. Space must 

 be available for holding several species of 

 fish, sometimes in rather large numbers. 

 The facilities to meet this need are grouped 

 in the fish-holding area. There are 10 

 circular steel tanks 1 1/2 feet deep (four 



figure 10. — An experimental apparatus used in studies of fingerling 

 responses to water flow. Visible between rear boxes are tubes 

 connecting heat-exchange coils in boxes to temperature control 

 unit. The suspended lights are connected through a variable 

 transformer for light intensity control. 



