pipe of appropriate height located 

 hotwoon tlio oiul Avail uiul the screen. 



The r;uH'\va_v-t y|)c rcarino- pond 

 lias sonic disadvantages. A very 

 substantial supply of water is re- 

 quired, although this could be re- 

 used in other poiuls in a series. 

 Young fish show a tendency to accu- 

 mulate at the inflow end of the 

 pond, thus apparently not utilizing 

 clliciently the space pi-ovided. 

 However, most efficient utilization 

 of the pond space by stocking the 

 pond to near capacity will result 

 ill better dispersion of the fish. It 

 is believed that the foregoing, if a 

 disadvantage, is minor as compared 

 to the advantages of this type of 

 pond in disease inhibition, ease of 

 feeding:, treatment for disease, and 

 handling of fish. 



The Washington State Depart- 

 ment of Game has used most suc- 

 cessfully a circular concrete pond, 

 usuallv 4:0 feet in diameter, about 



24: inches in water dcptli, and hav- 

 ing a very slight bottom sh)pe to- 

 ward the center staiid-i)ipe outlet, 

 which is surrounded by a square 

 screen. Exceptional weights of 

 trout have been produced from 

 these ponds. 



The circular pond i'e(|uires a 

 minimum of water, and its use is ad- 

 vantageous where water supplies 

 are limited. Because of the con- 

 tinuous circular How of water, how- 

 ever, disease organisms have greater 

 o})portunity to attack the fish and 

 disease treatments are more diffi- 

 cult. 



The Washington State Depart- 

 ment of Fisheries and the Oregon 

 Fish Commission favor a rectan- 

 gular pond with a center partition 

 that stops short of the end walls to 

 permit circulation of the water. 

 (See fig-. 23.) In some of these 

 ponds the inflow and outflow are at 

 the same end of the pond. In later 



Figure 23. — Salmon rearing ponds at the Green River Hatchery of the Wasliingtoii 

 Department of Fisheries. 



47 



