Raceways, Silos, and Circular Pools 



Raceways, silos, and circular pools constructed of cement, 

 fiberglass, or metal are examples of intensive cultural systems. 

 They are easy to clean, do not require large tracts of land, and 

 are not prone to heavy growth of aquatic vegetation. 



Most trout and salmon in the U.S. are reared in raceways. Raceways 

 are usually rectangular in shape and longer than they are wide. 

 They are usually placed end-to-end in series with water flowing 

 from one into another. Circular pools are typically shallow and 

 have a center drain. Silos are very deep; circular pools are 

 constructed above ground or are partially buried in the ground. 



Closed Systems 



Intensive cultural systems require large amounts of water and are 

 usually open, flow-through systems. The water flows through each 

 pool one time only. It may flow through one or more successive 

 pools, but then it is discharged to a drainage ditch, creek, or 

 river following settling of sediments in a settling basin. 



In a closed system, the water is reused after it is treated. It 

 must have all settleable solids and dissolved wastes removed, it 

 must be re-aerated, and in some instances disinfected. 



Closed systems are costly and difficult to construct, operate, and 

 maintain. However, with water becoming a more valuable commodity 

 and with pumping costs increasing, it is becoming more popular to 

 investigate reuse of water. Refinements in reuse systems are 

 expected and it is anticipated their use will increase with time. 



Cage and Pen Culture 



Cage and pen culture are essentially the same. The basic ■-■-■! L 

 difference is in the size of the enclosure. Generally speaking, 

 cage culture is practiced in freshwater, whereas pen culture is 

 practiced in marine waters. Cages and pens lend themselves well to 

 bodies of water which cannot be drained or otherwise manipulated to 

 facilitate harvesting. 



Cages are generally rafted two abreast and are worked from a boat. 

 Pens can be rafted four or more abreast. There are generally 

 walkways between rafts of pens and a serviceway the length of the 

 pens. Both cages and pens must be anchored in locations that allow 

 sufficient space between the bottom of the container and the bottom 

 of the stream, lake, or bay to allow wastes to settle out of the 

 enclosures . 



Species reared using these techniques include catfish, trout, 

 salmon, and many others. In some instances, cages have been 

 double-cropped with catfish being reared during the warmer, summer 



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