are involved. The farming of oyster, abalone, clam, 

 algae in Japan, and of milkfish in South Asian coun- 

 tries are of this type. 



A new experiment in the culture of red sea bream 

 is based on conditioning the fish to respond to 

 sounds. The seedlings, 20-50 mm in total length, are 

 kept in floating cages and trained with sound and 

 feeding of pellets. Within 2-8 wk, they are adapted to 

 sound of certain frequency (100-600 Hz) and develop 

 the habit of gathering around a feeding place every 

 time the sound discharges. After they obtain this 

 habit, the fish are liberated into natural waters, and 

 most of them retain the habit and do not scatter. 

 Although a small amount of pellets is necessary to 

 feed them, they can eat more natural foods for their 

 growth. Therefore, this idea could be categorized as 

 a tlsh farming. 



SEEDLING PRODUCTION 



The first step and one of the key points of fish 

 farming process is the seedling production. At the 

 incipient period, zygotes, larvae, and young fish col- 

 lected from natural waters are mainly used as seed- 

 lings, but artificial seedling production techniques 

 have been developed for important species and these 

 techniques are applied for the actual farming opera- 

 tions. The process is briefly shown in Figure 3. 



Matured adults from wild stocks are still used to 

 obtain eggs and sperm in most cases, but research to 

 develop techniques for obtaining eggs from adults 

 reared to maturity in captivity are in progress. 



In order to obtain zygotes, stripping and artifi- 

 cial spawning methods are sometimes used, but most 

 species can be induced to spawn naturally in artifi- 

 cially controlled tanks. Matured adults are put in a 

 tank of water, and the zygotes are collected after 

 spawning and fertilization occur. Then, the eggs are 

 transferred into a rearing facility such as a tank or 



aquarium. For some species, matured adults are put 

 directly into the larval rearing tank and removed 

 after spawning. 



The zygotes are reared in tanks of still water, but 

 slow running water can be used for larvae after they 

 reach certain sizes. With some species, the larvae 

 are transferred to floating cages until they reach 

 seedling size, but with shrimp, the larvae are kept in 

 the same tank till they reach seedling size. In this 

 case, control of population density to achieve the 

 desired numbers of final stage is important. The size 

 of seedlings varies depending on the purpose and 

 environmental conditions of receiving waters. 



The planned numbers of seedlings to be produced 

 in five centers in 1971 fiscal year are shown in Table 

 1. The prefectural centers are also producing some 

 seedlings, but their main purpose is the development 

 of culture methods. 



Breeder 

 Collection 



Breeder 

 Reoring 



Spowning Stripping 



Natural Zygote Collection 



Natural Larva Collection 



Natural Young Collection 



Figure 3. — Seedling production process. 



Table 1.— Planned production of seedlings in five centers of Farming Fisheries 



Association in 1971 . 



Organisms 



Season 



Number of 

 production 



Size 



29 



