ESTABLISHING THE HATCHERY 



lines always lead from the deepest 

 part of the pond to a convenient 

 watercourse that will carry off the 

 drainage water. 



Ponds should be so constructed 

 that the minim\im depth at the 

 shallow end is about 2 feet. Ponds 

 to be used for propa<ration purposes 

 should be sloped so that they are at 

 least 5 to 6 feet deep at the outlet. 

 Ponds used for holding fish through 

 the winter must be at least 10 to 12 

 feet deep in the Northern States; 

 however, the size of the pond will, 

 to some extent, determine the depth 

 at the outlet. 



The pond bottom should be sloped 

 from the sides and ends toward the 

 center and the center sloped from 

 the shallow end to the outlet. The 

 grade through the centerline of the 

 pond should be not less than 1 foot 

 for each 100 feet of pond length. 

 Where a series of hatchery ponds 

 is being constructed, the ponds are 

 partly above and partly below nat- 

 ural ground level. 



The type of equipment most 

 economical to use for excavating 

 a series of ponds depends on the 

 size of the job and the distance 

 that earth must be moved. Horse- 

 drawn equipment is economical 

 only for small jobs and short 

 hauls, but may be used for larger 

 jobs if it is the only equipment 

 available. With horses, a slip 

 scraper may be used economically 

 for moving earth as much as 50 

 feet, but for distances of more 

 than 150 feet the cost is' so great 

 that some other type of equipment 

 should be considered. If horses 



are used for longer distances, a 

 four-horse-loaded, two-horse-trans- 

 port wheeler should be used. 



Maximum efficiency may be ob- 

 tained with a 35-dhp (D-4) trac- 

 tor bulldozer at distances from 100 

 to 150 feet and where the grade 

 is not more than 5 percent. As 

 the grade increases, the efficiency 

 of a bulldozer decreases rapidly. 

 A self-loading, c a r r y i n g-type 

 scraper should be used at distances 

 greater than 150 feet. On larger 

 jobs, or where hauls are more than 

 500 feet, a 11-3-dhp tracktype trac- 

 tor is more economical. Of course, 

 availability of equipment may be 

 the decisive factor in most cases. 



Structures. — The types of struc- 

 tures to be used in conjunction 

 with hatchery layouts are largely 

 a matter of preference, but experi- 

 ence has shown that adequate con- 

 struction is highly advantageous. 

 Likewise, experience has demon- 

 strated that adequate construction 

 is more economical than skimping 

 on sizes and materials. Thus, pipe- 

 lines of sufficient size are more eco- 

 nomical than pipelines that are too 

 small. In the past, tile drainlines, 

 caulked with cement, have been 

 used extensively because the origi- 

 nal construction cost is lower. Un- 

 fortunately, there have been many 

 failures with these lines on ac- 

 count of loose caulking, entrance 

 of tree roots, pressure from the 

 fill, and for other I'easons. 



Great advances have been made 

 in the last few years in pipeline 

 fabrication. Among the types re- 

 cently developed, the most suitable 



14 



