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					Aqfs-601                        Lecture no#2                        04-03-11


       Advantages & Disadvantages of the Aquaculture

   Advantages :
       Helps insure a supply of desired aquacrops (wild supplies may be very
         limited aquafarming helps insure availability).
       Can control environments of production (feeding fish nutritional ,wholesome
         feeds eliminates possibility of contamination with harmful substances ,such
         as pesticides).
       Helps provide nutrients essential in human diet.

Disadvantages :
             o Technology not available for many possible crops.
             o Lack of knowledge about aquaculture.
             o Competition from wild fish & sea food.

Types of Aquaculture Production Systems:
       Level of Intensity :
                             Intensity refers to diversity (crowding together) of the
   aquacrop being produced.It may be Extensive , Intensive & Intermediate.
        Extensive systems involve low population density, minimal control over the sytem
   ,little intervention by the farmer,e.g. small natural or artificial ponds or lakes.
       Intensive systems involve producing aquacrops at a high rate of
   stocking.Considerable skill management & financial investment is needed .Tanks
   and Raceways are commonly used with continuously flowing water.The potential for
   returns is greater than extensive systems .
      Intermediate systems involve some principles of both extensive and intensive
   systems.In this artificial ponds are used ,fish are stocked at a rate requiring feed &
   water aeration but not in flowing water .Most catfish farming uses intermediate
   systems.

      Kind of Water Facility :
                                  It refers to design of the water enclosure & water
   movement .
      Water enclosures include ponds,cages,raceways & tanks.In pond culture, aquacrop
   is placed in the pond without restriction by cages & pens .Cages are used to confine
   fish to a certain area of the water .Raceways are long narrow structures that use
   flowing water.Tanks may be round or rectangular & use flowing water.
     Water movement refers to whether or not water in enclosure flows.The density at
   which fish can be stocked depends on the rate of water flow.

      Type of System :




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                        Classified on the basis of the use and re-use of water.They may
range from closed to open.
  An open system is one in which water is pumped in at one place & removed at
another .The water is used once and discarded .This involve running water into a
holding pond or into a river.Enviornmental regulations may not allow certain water to
be run directly into streams .
  Water may be re-used by flowing from one tank to other to another in series .Water
is not filtered to remove uneaten suspended feed .
  Recirculation involves pumping the water back through the same water facility.The
water is often re-conditioned, it may involve filtering , aerating procedures to keep
water of high quality.
  A closed system is one in which no new water is added ,involves filtering and
recycling of water, and it must be treated to remove uneaten feed , fish excrements.

   Water Temperature :
                             Different crops require varying temperatures.It may be
cold , cool ,or warm.It is important for potential aquafarmer to select an aquacrop
suitable to environment.

   Kind of Species :
                     Monoculture is a production system in which only 1 species is
grown at a time.
  Polyculture involves growing two or more species together.The species need to be
compatible in behavior & environmental requirements,in a good polyculture ,species
do not prey on each other , also do not directly compete with each other for food.




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