The aquaculture of sea bass, Lateolabrax japonicus
1. Scientific name: Lateolabrax japonicus
2. Common name: Spotted sea bass
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.
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℃. 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
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.