iv-no 



(1) Rearing aquatic species from selectively bred strains to 

 commercial size under controlled conditions where the opti- 

 mum requirements for food, temperature, salinity, and other 

 physiological and environmental needs are provided; predators 

 and competitors are eliminated and diseases control led* and 

 highly mechanized methods are used to reduce labor costs. 

 This is the ultimate in aquacultural operations and has been 

 achieved only for a few species (e.g., carp). 



(2) Rearing aquatic species in natural or artificial enclosures 

 to commercial size, with or without supplemental feeding, 

 predator control, environmental adjustment, and selective 

 breeding. Enclosures may be man-made tanks, natural or 

 artificial ponds, or enclosed areas of the sea. Such tech- 

 niques are now used for the production of oysters, clams, 

 shrimp, catfish, carp, and baitfish. (Figure TV. 2. 10). 



(3) Rearing aquatic species in hatcheries through the juvenile 

 stages, the period of greatest natural mortality, to stock 

 natural areas. This effort may be used to replenish stock 

 reduced by natural or artificial changes in the environ- 

 ment, overfishing or other factors, or to introduce new 

 species into an environment. Such methods are bein? used 

 to maintain salmon and trout fisheries and to provide sport 

 fish in areas of heavy fishing pressure. 



