The Chupei branch of the Taiwan Fishery Research Institute has recently succeeded in its efforts to raise Japanese sea bass (Lateolabrax japonicus), a carnivorous sea fish, in fresh water after artificial insemination. The fish, found around the coasts of China, Korea and Japan, is rich in protein and is said to be good for convalescing patients.
Sea bass adapt easily to various temperatures and degrees of salinity, enabling them to survive in fresh water. Since the catch from the sea is limited, prices have been soaring recently, reaching as high as NT$300 (US$8) a kilogram in the winter harvesting season, and three times as much for the rest of the year.
At first, attempts to cultivate sea bass in fresh water failed because of the difficulty in gathering spawn and ignorance of the habits and needs of the fish. The traditional way of raising Japanese sea bass has proved risky and primitive. Most fishermen mixed bass fry with ground feeders such as carp in fishponds. The idea was that the bass would devour undesirable species, and retain the density of food fish in the pond. It proved difficult, however, to decide how many fish to release. If the number was too low, the undesirable species would proliferate. If too many were released, the bass would feed on useful species, or even eat each other.
When the Chupei institute successfully raised 3,000 baby bass in fresh water at the beginning of this year, fish culture in the Republic of China reached a new level.
Roughly cylindrical in shape, the Japanese sea bass has a forked tail, small eyes and a large mouth. It is silvery gray above, and silvery white on the sides. Perng Ching-jou, one of the researchers on the special team for the development of the sea bass, said that the fish must be introduced to fresh water gradually over a period of about a week. Results so far have been satisfactory, as some 80 to 90 percent of the baby bass have survived. If the fish are transferred directly from the sea to fresh water, however, the survival rate is less than 10 percent.
Another breakthrough achieved by the institute is to feed the fish on a meal made of ground up eels and fish roe, which is mixed with soybean powder to gradually wean the fish from their carnivorous habits.
It is particularly important to keep the water in which the bass are bred clean and aerated, since they need more oxygen than most species, and cannot survive in polluted water. In addition, fish must be segregated according to their size, since big fish will readily eat smaller ones, even though they are the same species.
Since it is difficult to obtain high-quality fish from mature eggs, the institute workers add Vitamin E to the food to speed up the growth of roe in captive fish, and inject hormones to assist the development of the spawn. As the male bass are infertile in fresh water, the eggs are placed in brackish water for artificial insemination.
The Chupei institute has completed the artificial insemination procedures for the first time in the world. Although Japanese experts have completed the same tests, they failed to include the hormone treatment. The institute is now planning to breed baby bass in large quantities and present seminars on the most modern techniques used in raising the fish so that fishermen can share the benefits of the experiments. Eventually, local gourmets will not have to pay such a high price for their delicacy.
[Picture Caption]
Left: The Japanese sea bass is rich in protein and is said to be good for convalescing patients. Below: Feeding the fish. Right: Researchers of the Chupei Branch of the Taiwan Fishery Research Institute catching the fish.
Above: Researchers inject hormone to assist the development of the spawn, and conduct research on its effect. Opposite: The baby sea bass.
Researchers of the Chupei Branch of the Taiwan Fishery Research Institute catching the fish.
Researchers inject hormone to assist the development of the spawn, and conduct research on its effect.
Researchers inject hormone to assist the development of the spawn, and conduct research on its effect.
Researchers inject hormone to assist the development of the spawn, and conduct research on its effect.
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