The aquaculture of sea bass, Lateolabrax japonicus 

1. Scientific name: Lateolabrax japonicus  

2. Common name: Spotted sea bass

3. Ecology

   The taxonomical position of the sea bass is belonging to Genus Lateolabrax., Suborder Percoidei, Order Perciformes, Class Actinopterygi. The species distribute from western to southern coasts of Korean peninsula.  The species is also found in Japan, some parts of China, and Taiwan. Although the fingerlings inhabit the coasts, they have a distinct migration. The fish move toward brackish water in the inner bay during summer and migrate to deep sea during fall and winter.

4. Aquaculture

   L. japonicus are carnivorous.  They grow relatively fast; up to about 300§® in body length in 2 years and 600§® in 3¡­4 years. The fish are voracious even in the lower water temperature of below 10¡É. The wild L. japonicus become mature October and December in captivity. Indoor maturing and breeding is conditioned by hormonal treatment and light cycle. Hormonal treatment is done through injection by syringe and feeding hormone enriched pellets. As for breeding fish, those that migrate to lay eggs during autumn or winter (from October to February next year) to brackish water of the shore or the mouth of river are mainly targeted.  Capturing of breeding fish is done by using pound net and spawning is done quickly.  Recently, migrating resource has been annually decreasing and securing of breeding fish is becoming difficult.  Appropriate ratio of gender for breeding is 1 female for 2 male fish.
  Breeding period is from October to December(about 30 days) and spawns once during breeding period (main breeding period of sea bass in Korea is from late October to early November, Bohai bay: August to November).  Spawning water temperature is 16¡­19  and 50 ¡­80§¯ breeding fish spawns about 2 million to 15 million eggs.  As for fertilization, best result comes from dry fertilization with 1 female to 4 to 5 male ratio.  
  Spawning to hatching period depends on the water temperature but at 18¡­20  it takes about 54 hours and about 60 hours at 16¡­17 .
  The size of hatchlings are about 3.5¡­3.6§®.  After 2 to 3 days yolk will be absorbed and mouth will open at which point the fingerling will start feeding.  Supply rotifer at this point and after 20 days of hatching, mix it with Artemia.  Size of a fingerling is about 10§® and mixed feed should be supplied after 30 days.  Growth rate of young sea bass is as following: length about 9.2§® after 30days, 21.4§® after 60days, 42.2§® after 90 days, and 65.8§® after 130 days.  They often die in mass during 30 to 40 days period possibly due to deformities and other abnormalities.  They also often die in mass at 60 days period due to failed conversion from mixed feed which needs close attention.  
  As discussed above, success of seedling production of sea bass depends on; sufficient supply of nutrition to fingerlings, water quality management, and water temperature control during winter.  Stable adult fish security, economy of heated water farming, and disease control should be taken in to consideration in seedling production.
   L. japonicus cultivation is mainly done with caged culture and embankment method.  Recently inland circulation filtering domestication through freshwater domestication is being developed.  As for basic raising method; feeding is active at 10¡­30  water temperature but will eat less at below 10  and over 34.10% of its own body mass is appropriate for one day's feeding and the amount should be increased as the fish grows.  Appropriate frequency of feeding is 1¡­2 times per day.  Cultivation density is appropriate at 500¡­750 basses per 1 tone at size of 15§¯ and they can grow 400¡­500g per one year in caged culture.  Recent fresh water domestication has shown 10% increase in growth rate compared caged cultivation.  
  There are many reports of deformed fingerlings during seedling production period. No particular diseases have been reported for raising period.  Prevention methods of dipping fish in Formalin or using photosynthetic antibiotics are known to be a usual practice.  Generally, such prevention methods are used on seedlings such as flatfish.