THE STATUS OF SEABASS CULTURE IN CHINA

Zhuang Zhimeng *

I. Introduction

Due to tropical and sub-tropical conditions, soil fertility, abundance of rainfall and food organisms, aquaculture in China, especially freshwater aquaculture in the southern parts, has been popular and has had a long history. The available areas for aquaculture in Guangdong, Guangxi and Hainan Provinces, which have suitable sites for seabass culture, reaches about 200,000 hectares.

Seabass culture in China started in 1976 and has developed considerable. This paper gives a brief review of the Chinese seabass culture.

II. Seabass culture - History and its evolution

Seabass were first introduced in Dongguang City, Guangdong Province from Thailand and were polycultured in earthen ponds.

In 1979, the Thai Government donated 2,000 seabass fry to the South China Sea Fisheries Research Institute. These fry were cultured in Yingken, Zhuhai City. Newly hatched larvae were introduced and cultured extensively in Baoan County.

In 1983 and 1985, NACA made available 6,000 and 4,000 fry respectively to Huiyang, Shenzhen and Dongguang Cities.

Owing to the fast growth and delicate taste of seabass, the Chinese Government paid more attention to seabass research and development. Since 1985, many local governments, such as Dongguang, Doumen, Zhuhai, Panyi and Taishan have established seabass fish farming stations and the total culture area has increased to 200 hectares. The number of netcage monoculture in 1985 was 350 netcages. Considerable polyculture is also carried out.

* Assistant Resercher, Yellow Sea Fisheries Research Institute, 19 Laiyang Road, Qingdao, P. R. China

III. Culture regime

As mentioned above, there was no seabass culture in China until 1976. At present there are four methods used in seabass culture in China:

a. Monoculture

Seabass is the dominant species in the ponds (density of seabass: 1.0–1.4 × 10⁴ ind./ha, fry size: 7 cm in TL) cultured with some omnivorous fish or shrimps. The pond size is 0.3–1.2 ha. After culturing for 120–180 days, with timely feeding, water exchange and size-grading, the fish are harvested. During the harvest seasons, water temperature decreases to 20 °C and seabass reaches the market size of 0.5–1.0 kg. Generally the output is about 3,750 kg/ha in the monoculture system.

Table 1. Seabass culture areas and their outputs, 1987.

Note: Netcage size is 3.0 × 3.0 m.

b. Polyculture

Other commercial fish such as mullet, bighead, silver carp, grass carp and black carp, are cultured together with a few seabass by means of extensive culture, without artificial feeding. The stock density of seabass is 150–300 ind./ha.

c. Near shore Netcage Culture

Each cage raft comprises 6 to 12 netcages installed where the water depth is 6–10 m in the near shore of Huiyang, Zhuhai, and Hainan. The netcage is 3 × 3 × 3 m. All the fry used in these areas are imported from Thailand, the Philippines, Singapore and Taiwan, via Hongkong. The fry size is 2–4 inch in TL. Culture density is about 150–200 ind./m³. Harvest season is just before winter.

d. Earth-Pond Culture

Few fish farming stations in China extensively rear seabass in large-scale earthponds (>40 ha). The fish are harvested in winter.

IV. Production of seabass fry

At present, most of the fry for culture in China are imported from Thailand and Taiwan, via Hongkong. Some of them are directly transported to Guangzhou. In 1988, the quantity of imported fry and fingerling was about 2.4 millions.

Studies on culture techniques of seabass began in 1983 by means of 2 million Thai-supplied fertilized eggs which were provided to Mr. Shao Yiran and reared in Shatoujiao Fisheries Farm and Yantian Mariculture Experiment Base under the South China Sea Fisheries Research Institute. Both are in Shenzhen City. Unfortunately, the results were poor and a survival rate of only 1 % was obtained.

Since 1984, the Chinese Government has made budgetary provisions for the seabass reproduction project. The project was undertaken in Zhuhai where seabass broodstock were introduced from Thailand every year in order to obtain fry by means of artificial maturation and spawning.

Up to now, there has been no successful conclusion. In 1986, 80,000 fry (TL 2.5 cm) were obtained from the seabass hatchery in Zhanjiang, Guangdong Province.

The culture history of seabass in China is not as long as that in other Asian regions. However, the central and local Chinese Governments are investing on seabass production in the southern parts of China.

V. Problems

a. Fry availability.

About 95 % of the seabass juveniles used in China are imported. The main problem that hampers the development of seabass culture is the difficulty in transporting and transacting the import formalities, the difficulty of planning the production, and high costs.

b. Poor culture techniques and management.

Lack of skill and experience in seabass culture leads to low output, high cost, uneven size, and low disease resistance in many seabass culture stations of China.

c. Wintering problems.

In the winter season, occasionally the water temperature in Guangdong drops below 20 °C. In such event, seabass stop feeding and may even die. For instance, on the 29th of November 1987, 95 percent of the seabass in Guangdong died due to cold weather (-17 °C).

VI. Future plans

Seabass has been considered as a profitable culture species due to its high price, fast growth and eurysaline, and the availability of culture techniques from other countries. As to the development of seabass culture in China in the near future, we will focus on the following:

1. Establish some modern seabass hatcheries, emphasizing broodstock rearing and food organism culture.

2. Set up some nursery stations in Dongguang, Donmen, Taishan and Shenzhen to rear 15-day-old juvenile in order to increase the survival rate and cut down on costs.

3. Train more technicians for seabass farming.

4. Solve feed shortage which would require the development of some new food resource.

VII. Conclusion

It is a good opportunity for us to participate in this training course. We are sure that we can make more contributions to seabass culture in our country after this training. We also hope that we can share the experiences of other countries and learn from all of you.