ESTABLISHING THE HATCHERY 



and outlet combination should be 

 set at the toe of the levee and half- 

 way down one side of the pond at 

 the deepest end. 



An alternative type of construc- 

 tion involves the use of an outlet 

 box and the catch basin at some 

 point outside the pond (fig. 9). 

 The outlet box is similar to that 

 designed for a natural pond and 

 does not require the use of a screen. 

 All the water is drained through 

 the outlet to a catch basin outside 

 the pond. 



The outside seining, or catch, 

 basin is a concrete tank constructed 

 in such a way that water from the 

 pond outlet flows into it. Grooves 

 are provided for a screen and dam 

 boards. "Where the outlet from the 

 pond comes into the seining basin, 

 it is provided with an irrigation 

 gate or valve which may be shut 

 when desired. 



Most of the water from the pond 

 is drawn through the seining basin 

 until a considerable number of min- 

 nows come into it from the pond. 

 The outlet valve to the pond is 

 closed and the water in the basin 

 lowered until the majority of the 

 minnows can be removed to suitable 

 receptacles. This operation is re- 

 peated until all the water has been 

 drained from the pond and all the 

 minnows have been removed from 

 the seining basin and placed in 

 holding facilities. 



The type of construction with 

 ponds in a series along a water- 

 course or grouped in such a way 

 that a number of pond outlets can 

 bo brought into the seining basin 



is most economical, because more 

 than one pond can be drained into 

 the basin. If there is a large group 

 of ponds, the situation may not lend 

 itself to this type of construction, 

 because only one pond can be 

 drained at a time. Where there is 

 a basin in each pond, more than one 

 pond can be drained at a time — 

 often a very desirable procedure. 



Waterlines supplying the ponds 

 should be of sufficient size to fill the 

 ponds rapidly and to maintain 

 water levels. At least 4-inch, and 

 preferably 6-inch, pipes should be 

 run to each 1-acre pond. The main 

 supply lines from which these pipes 

 lead off should be designed in ac- 

 cordance with the number of ponds 

 supplied, the amount of water pres- 

 sure, and other factors. Cements- 

 asbestos pipe is ideal for the main 

 supply lines. These lines should be 

 laid in the dikes at the proper stage 

 of construction. 



There is some difference of opin- 

 ion regarding the proper location 

 of the water-supply lines to the in- 

 dividual ponds. Where the seining, 

 or catch, basin is located in the 

 pond, the supply line should be lo- 

 cated at the basin. This permits the 

 use of fresh water when the pond is 

 being drained and when the pond 

 water is muddy from frequent agi- 

 tation. It also provides a source of 

 fresh water to fill receptacles used 

 to transport fish from the pond. 

 Except in those ponds used for the 

 l)ropagation of stream-breeding 

 species such as the creek chub, there 

 seems little in favor of having the 

 water supply at the end opposite the 

 outlet. 



20 



