CHAPTER 2 

 CURRENT TECHNOLOGIES 



This chapter contains an overview of technologies employed by 

 aquaculturists in the U.S. Subject areas include: production 

 methods, genetics and reproduction, nutrition and diets, water and 

 waste management, control of problem organisms, harvesting, 

 transportation, and processing and marketing. For greater detail 

 the reader should consult the individual species plans in Volume 

 II. 



Production Methods 



Pond Culture of Freshwater Finfish 



In the U.S., ponds are the most commonly used facilities for fish 

 culture. The size, shape, and depth of ponds can vary 

 considerably. Regardless of these factors, it is desirable to have 

 ponds that are easy to harvest, drain, and refill rapidly and 

 completely. 



Many species of fish lend themselves well to pond culture. Some 

 may be coldwater species such as trout, char, or salmon; they may 

 be coolwater species such as walleye, perch, muskellunge, or 

 northern pike, or they may be warmwater species such as carp, 

 catfish, tilapia, and many others. 



Most pond culture in the United States is monoculture in 

 nature — one species of fish is reared in each pond. However, some 

 polyculture is also practiced — two or more species being reared in 

 the same pond simultaneously. An example of this type of culture 

 is the rearing of tilapia or buffalofish with catfish. Catfish are 

 fed pelleted diets while the other species eat the wasted feed, 

 algae, and zooplankton. 



Early pond culture was a form of extensive culture. Generally, 

 broodstock were placed in a pond and allowed to spawn naturally. A 

 minimum amount of supplemental feed was provided and a minimum 

 amount of fertilizer was added to the ponds to generate food for 

 the young. At the end of the growing season the pond was emptied 

 and the remaining fish, usually a modest amount, were harvested. 



Intensive culture requires that broodstock be held in separate 

 ponds, be spawned artificially, and the young, in large numbers, be 

 placed in special rearing ponds. They are fed to promote fast 

 growth and then are periodically harvested. A comparison of yields 

 is quite dramatic. Extensive pond culture production ranges from 

 1,684 to 2,245 kilograms per hectare (1500 to 2000 pounds per 

 acre). Under intensive methods, annual yields may be 5,600 

 kilograms per hectare (5000 pounds per acre) or higher. 



10 



