Land-based culture system  

The dominant marine cultured species of Korea is Olive flounder ( Paralichthys olivaceus) and it is reared in land based raceway culture system.
Farms are usually located the south and west coast, especially This Je-je do which is the most southern part of Korea. Each farm usually produces about 110 ton (110,000kg) in a year. This is the average amount of products since some years with mean stock density 20kg/m. This product is purchased to Seoul and Japan by wholesaler.

 Water resource, quantity and quality

Raceway system is that water should be supplied constantly. If it is stopped it would be serious problem to the farm. The quantity of water required is dependent on the type of aquaculture system, species cultured, management practices, culture densities, skill of culturist, and so on. Therefore, it is difficult and foolhardy to generalize about water needs. There are four functions that a water supply must satisfy: evaporative losses, seepage losses, oxygen depletion, and waste disposal. In addition, water may be required for other uses of property such as fire protection, livestock watering, facility cleaning, irrigating crops, and residential use. The water budget should also be sufficient to take into account future plans for expansion.
In these aspects, this farm has quite good condition of water resource. The seawater is pumped from the open sea directly into head tank and then it is supplied into the fish tanks. There are usually six pumps. Four pumps are 100Hps and they usually are used to pulling seawater. Four pipes are contacted and it is buried, that away 150m from coastline. And pipe's diameter is 500mm. Two pumps are back up pumps. Normally, just two 100 Hps pumps are used. But emergency situation for instance when one is broken down, other back up pumps would be used.
And also there are two other pumps for pulling underground water powered 75Hps and 40Hps, respectively.    The min/max/mean water temperature, dissolved oxygen, dissolved hydrogen density and salinity of Jeju area in 2002 are shown in below table.

 Security  

There is an alarm system which acts water level is changed. The water alarm prepared for warning low level, power failure and an instant power failure. This system was set up by special line of business. Check everyday and once a month the professional comes and check.  

 Nutrition and feed

Feed efficient diets and well nutrition is decide that its healthy and price of products. So to grow more healthy environmental conditions, diets, and nutrition is very important part. At these factors, if just careless of one factor it causes disease. The most failures will be at this situation.
After larval stage, the diet or nutrition is very important part of production cost for marketable flatfish. The most efficient and economic diets have to be chosen. Moisture pellets are still in current use for flounder in Korea. Mix the fishes like mackerel, gizzard shad which has well nutritive and fresh condition. Then press them which fishes can eat easily. This farm also makes own feeds in the farm, just make that quantity of a day's supplement, with small fish and commercial powder diets.

 Natural hazards

Almost of fish farms have chance to meet some natural hazards. The products are always threatened by several hazards just like water pollution, flood, predators, algae, shipping, etc. As usual there are several harmful factors for aquaculture in the nature in Je-ju. The most frequent factor is Typhoon. About 7 typhoons faced every year but only 1-2 typhoon landed in the Korean peninsula. Of which the grade of power was not A usually B or C. Therefore landed typhoon, we can ignore for aquaculture industry. Second factor is Red tide. Red tide is quite often happen in the South sea Even if the red tide is very harmful for cage culture. But the land based flounder culture system is quite safe due to use underground seawater well. Other factor is diseases. There are virus, bacterial and parasitic diseases around culture system. But usually only 10-15 % of mortality has been reported from infected areas. From the daily based of fish rearing record, the mortality of this farm due to diseases and unknown dead fish is under 10%.  

          
A typical view of land-based culture tanks. Most are round and rectangular in shape.

          
Pipe lines connected to the reservoirs or to the culture tanks directly
 

         
Reservoirs from which the cultured waters go to the culture tanks by gravity
 

         
                        A generator for emergency