In this process, the utilization of natural produc- 

 tivity is an indispensable condition for farming 

 fisheries which is different from ordinary aquacul- 

 ture in which the growth of species, such as trout and 

 eels, depends almost entirely upon introduced 

 foods. 



The following items are considered in selecting 

 suitable organisms for farming: 



1 ) They should adapt easily to farming operation. 



2) Their growth rate should be high. 



3) They should have a reasonably high market 

 value as a product. 



4) The seedlings can be supplied easily from a 

 hatchery or from natural reproduction. 



5) The feeding habits of larvae and/or young 

 should be clearly known ecologically and physiolog- 

 ically. 



6) Foods for the organisms should be readily 

 available and cheap. 



7) They should be resistant to diseases, or 

 disease-control methods should be available. 



The satisfaction of these requirements is espe- 

 cially significant for a successful operation. How- 

 ever, if demand for a species is great and the market 

 value is high, greater efforts to develop farming 

 techniques for the species will be justified, even 

 though that species would be difficult to farm. The 

 most important consideration in planning of fish 

 farming may not be the technical problems, but the 

 development of an economical system. Composite 

 planning will be required from both technical and 

 economical points of view. 



As a special case, geographical transplantation of 

 organisms is ideal for some species. Rapid growth 

 and greater production can be expected when north- 

 ern species are transplanted to southern regions. 

 Some places isolated from a source of organisms 

 sometimes have few native species, but have food 

 and space capacity for additional species. So, when 

 the investigation for farming is carried out. the idea 

 of introducing a new species should be considered. 



TWO TYPES OF FISH FARMING 



Present and/or proposed farming fisheries could 

 be classified into two types: 1 ) stock recruitment and 

 2) artificial control, as shown in Figure 2. 



Stock Recruitment Type 



In stock recruitment type of farming, the seedlings 



are transferred from the operation centers or hatch- 

 eries to a temporarily constructed acclimation facil- 

 ity. This procedure allows the seedlings to adapt to 

 the environmental conditions of the recei\ing waters 

 and to naturalize their behavior while protected from 

 predators. After certain periods, they are released 

 into natural waters forgrowth. In this case, the plant- 

 ing sites are determined from the results of scientific 

 investigation of the environments and distribution 

 and behavior of natural stocks. 



For example, when a shrimp release program is 

 planned, investigations are carried out in advance to 

 determine the suitability of various places for shrimp 

 growth and the best place is selected for the planting. 

 Places where natural shrimps thrive are likely to be 

 satisfactory release sites. 



When environmental conditions in an area are ac- 

 ceptable for the planned species and when results of 

 scientific investigations show that the adaptation 

 and the naturalization are unnecessary, seedlings are 

 released directly into the waters. Otherwise, accli- 

 mation techniques are applied. In the case of shrimp, 

 the seedlings are acclimated in net enclosures for 1 -3 

 wk depending upon the situation. 



The stock recruitment type of farming is practiced 

 at present with prawn, blue crab, and several species 

 of fin fish. 



Artificial Control Type 



The artificial control type of farming is usually 

 smaller in scale than the stock recruitment type, and 

 frequently some facilities or mechanical equipment 



Fish Forming 



ArTif iciol 

 Control Typ* 



Stock 



Recruitment 



Type 



Seedling 

 Production 



Acclimotion 



Nursing 



Seedling 

 Production 



Ulilliotion 



of 



Noturol Productivity 



^ Acclimotion Releasing 



i 



Releosing 

 ^ Growing 



Horveat Recapture 



Figure 2. — Brief diagram of fish r;irniing in Japan. 



28 



