Competitors and Predators 



Competitors are not uncommon in culture systems and include 

 microorganisms and higher forms of plants and animals. However, a 

 plant or animal that may be a competitor for one cultured species 

 could be a beneficial source of food or protection for another. 

 Predators, on the other hand, are generally more easily identified, 

 and include some zooplankton, insects, crustaceans, fishes, 

 reptiles, mammals, and birds. Some animals may be predatory on a 

 cultured species for only a portion of the life cycle — for 

 example, during juvenile stages. 



Effective and economical techniques exist for controlling some 

 predators. However, for others it is difficult to control or 

 eliminate the predator without harming the cultured organism. 



Harvesting 



Ponds : • . i- I 



Harvesting techniques employed in ponds depend on the size range of 

 the animals, the intensity of production, and species cultured. 

 Technology exists for harvesting most cultured aquatic animals. 

 Some harvest systems, such as those used in intensive catfish pond 

 culture, are well developed and modern. For other species, 

 harvesting equipment and techniques need to be improved. Animals 

 reared for recreational fishing have special handling and '-"■>''' 

 transporting requirements which are not readily adaptable to 

 mechanized harvesting methods and thus will remain labor-intensive 

 and expensive. 



Raceways 



Harvesting techniques for raceways are generally well developed. 

 Some of this technology is not being used by the commercial 

 industry or governmental agencies because of the cost of 

 redesigning the present facilities to install various equipment 

 items. The high labor costs of nonmechanized harvesting will 

 encourage the inclusion of mechanized methods in future facility 

 construction. 



Cages and Pens 



Harvesting is a major problem in cage and pen culture. Cages or 

 pens are usually located away from land and access is provided by 

 boat or barge. Pond and raceway harvesting techniques are 

 unworkable in this setting. At present, most cage- and pen-reared 

 fish must be dipped by hand and placed in containers — a 

 labor-intensive operation. Another disadvantage is that net pens 

 or cages do not permit partial or selective harvest. 



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