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Present status and prospects of sea cucumber industry in China

Jiaxin Chen


Yellow Sea Fisheries Research Institute, Qingdao, China

Abstract

In China there are about 20 species of edible sea cucumbers that have long been considered as a traditional medicine and tonic food. Nutrient analyses show that either the body wall or the intestine of sea cucumber has a higher nutrient value. The protein content of dried sea cucumber is more than 50 % in most edible species, while glucosaminoglycan has been detected in sea cucumber providing evidence of the pharmaceutical value of the sea cucumber. The clinical function of sea cucumber is reviewed in this paper. In order to meet the increasing demand and to protect the natural resources, the highest priority for fisheries authorities has been given to seed production of sea cucumber (Apostichopus japonicus) and to development of techniques for farming and ranching. Sea cucumber farming and ranching is a key part of the aquaculture sector in northern China, including the Liaoning and Shandong Provinces. The total landings from farming reached over 5 800 tonnes (dry weight) in 2002, with the sea cucumber either directly sold to restaurants or processed as dried edible and medicinal products. China has become the largest producer of sea cucumber worldwide. Farming methods and ranching techniques were introduced. The confusion of the quality of and species used for processed products have become the main issues retarding market development, while over-exploitation of earthen ponds used for farming sea cucumber could possibly induce a disaster similar to the shrimp viral diseases experienced in the early 1990s. Suggestions for further development involves seed production, new models of farming and ranching, quality control of final products as well as proper resource management to protecting these endangered species.

Keywords: Apostichopus japonicus, nutrients, farming and ranching, trade

Introduction

There are about 134 species (Liao, 1997) of sea cucumbers distributed in China's seas. Of these, about 28 species (Table 1) are considered edible (Zhang, 1954, 1958) or have pharmaceutical properties (Fan, 1979). Most of the species are distributed in subtropical and tropical areas, with a few species, including Apostichopus japonicus, a high value species, existing in temperate waters. While most of the edible species belong to the Order Aspidochirotida, a few species are also in the Order Dendrochirotida. Acaudina leucoprocta in the Order Moldavia is the only species in this Order to be used for edible purposes and is often called the "sea potato" in China (Fu, 1994).

Table 1. Edible sea cucumber distributed in China seas.

Latin name

Common name

Commercial value

Distribution

Order Aspidochirotida





Family Holothuriidae




Genus Actinopyga





A. echinites

Deep-water redfish

++

Taiwan, Guangdong, Xisha Archipelago, Hainan Island

A. lecanora

Stonefish

++

Xisha Archipelago, Hainan Island

A. mauritiana

Surf redfish

++

Taiwan, Hainan Island and Xisha Archipelago

A. miliaris

Blackfish

++

Hainan Island and Xisha Archipelago

Genus Bohadschia





B. argus

Tigerfish

++

Taiwan, Hainan Island and Xisha Archipelago

B. marmorata


++

Hainan Island and Xisha Archipelago

Genus Holothuria





H. (Halodeima) atra

Lollyfish

+

Taiwan, Hainan Island and Xisha Archipelago

H. (Halodeima) edulis

Pinkfish

+

Hainan Island and Xisha Archipelago

H. (Lessonothuria) pardalis


+

Taiwan, Hainan Island and Xisha Archipelago

H. (Mertensiothuria) fuscocinerea


+

Taiwan, Guangdong, Hainan Island and Xisha Archipelago

H. (Mertensiothuria) leucospilota


+

Fujian, Taiwan, Guangdong, Guangxi, Hainan Island, and Xisha Archipelago

H. (Mertensiothuria) pervicax


+

Taiwan, Hainan Island, and Xisha Archipelago

H. (Metriatyla) scabra

Sandfish

+++

Guangdong, Hainan Island, and Xisha archipelago

H. (Microthele) fuscogilva

White teatfish

+++

Xisha Archipelago

H. (Microthele) nobilis

Black teatfish

+++

Taiwan, Hainan Island, and Xisha Archipelago

H. (Selenkothuria) moebii


+

Fujian, Guangdong, Hainan Island

H. (Semperothuria) cinerascens


+

Taiwan, Guangdong, Hainan Island, and Xisha Archipelago

H. (Thymiosycia) arenicola


+

Taiwan, and Xisha Archipelago

H. (Thymiosycia) impatiens



Taiwan, Hainan and Xisha Archipelago

Family Stichopodidae




Genus Apostichopus





A. japonicus

Prickly sea cucumber

++++

Liaoning, Shandong, Hebei, Jiangsu

Genus Stichopus





S. chloronotus

Greenfish

++

Hainan Island, and Xisha Archipelago

S. horrens

Dragonfish

+

Taiwan, Hainan Island, and Xisha Archipelago

S. hermanni


++

Taiwan, Guangxi, Guangdong, Hainan Island, Xisha Archipelago

Genus Thelenota





T. ananas

Prickly redfish

++

Xisha Archipelago

T. anax

Amberfish

++

Xisha Archipelago

Order Dendrochirotida





Family Cucumariidae





Mensamaria intercedens


+

Fujian, Guangdong, Hainan Island

Order Moldavia





Family Caudinidae





Acaudina leucoprocta

+


Zhejiang, Fujian, Guangdong, Hainan Island

Note: symbol "+ " means commercial value, the values gradually increase from + to++++. The price is doubled 1 to 2 times approximately for each +.

The Chinese advocate the use of sea cucumber as a folk remedy. As early as the Ming Dynasty (1368-1644 BC), sea cucumbers were first recorded as a 'tonic' food in the Bencao Gangmu (Li, 1596 reprinted in 1994). Later, sea cucumber was also recognized as a tonic and a traditional medicine in other ancient literatures, i.e. Shiwu Bencao (Yao, Ming Dynasty, reprinted in 1994) and Bencao Gangmu Shiyi (Zhao, 1765, reprinted in 1954).

Chinese philosophy has long considered that food and medicine are one entity. It is, therefore, very popular for Chinese to regard food as a medicine for prevention and treatment of disease. For example, Sun Simiao, a court physician in the Tang Dynasty, said: "Treat an illness first with food. Only if this fails should medicine be prescribed." Hence, Chinese cooks have revered the sea cucumber since ancient times leading to a long tradition, especially amongst the coastal population, of consuming sea cucumber to the point where it has become part of the culture and customs of the coastal communities.

According to the principles and theory of traditional Chinese medicine, the sea cucumber nourishes the blood, vital essence (jing), kidney (qi) (treats disorders of the kidney system, including reproductive organs) and reduces dryness (especially of the intestines). It has a salty quality and warming nature. Common uses include treating weakness, impotence, debility of the aged, constipation due to intestinal dryness and frequent urination. Therefore, the Chinese consider sea cucumber as a tonic rather than a seafood item. Hence, the popular Chinese name for sea cucumber is "haishen ", which means, roughly, "ginseng of the sea".

Since the 1980s, the economic development of China has greatly improved the living standard of people and stimulated the consumption of tonic food and luxurious seafood, including sea cucumber. The consumption of sea cucumber has increased significantly. In order to meet the increasing demand, research and development of sea cucumber seed production, farming and enhancement has become a priority since the 1980s.

As early as the 1950s, artificially produced seeds of sea cucumber were tested (Zhang, 1954, 1958). However, the main progress was only achieved in the 1980s (Sui, 1985; Zhang and Liu, 1993). The advanced techniques dealing with seed production, culture and resources enhancement of sea cucumber, especially Apostichopus japonicus, involve three aspects:

As a result of this work, the output of sea cucumber reached 6 335 tonnes in 2002 (Anon, 2003), of which 5 865 tonnes were from cultured production and 470 tonnes from captured production (Table 5). Nevertheless, the output cannot meet the increasing demand; hence, China imports a great deal of dried sea cucumber from other countries via brokers in Hong Kong SAR (China). Owing to the lack of reliable data sources, it is difficult to provide precise figures of import levels of sea cucumbers, but prosperous businesses reveal that volumes are large.

In general, mariculture and sea ranching of sea cucumber have quickly become a prosperous sector in the northern part of China, and have gradually expanded towards the southern part including Fujian, Guangdong and Hainan Provinces. The total output of sea cucumber accounts for a small part in the entire output of fisheries, but its higher production value cannot be ignored. Recently, under the stimulation of large profits, capital investment has been continuously flowing into the sector and farming areas have sharply expanded. Hence, the rational development of, and further research into, sea cucumber production should be thoughtfully considered by relevant authorities, investors and farmers, as well as academic institutes.

Nutritional and medical value of sea cucumber

From the nutritional viewpoint, sea cucumber is an ideal tonic food. It is higher in protein and lower in fat (Table 2) than most other foods. The amino acids profile, especially for the essential amino acids (Table 3) and the presence of necessary trace elements (Table 4) makes sea cucumber a healthy food item.

Table 2. Comparison of main elements of different species of sea cucumber.

Item

Protein (%)

Fat (%)

Moisture (%)

Carbohydrate (%)

Ash (%)

Fresh body wall of AM1

11.52

0.03

87.83

0.38

0.99

Dried AM

68.53

0.55

8.25

-

7.56

Fresh body wall of TA2

16.64

0.27

76.97

2.47

1.60

Dried TA

69.72

3.70

8.55

-

9.51

Dried AJ3

55.51

1.85

21.55

-

21.09

Source: WangF. G., 1997; modified by ChenJ. X. 1 = Acaudina molpadioides; 2 = Thelenota ananas; 3 = Apostichopus japonicus.

Table 3. Comparison ofamino acid levels in seven species of sea cucumber.

Amino acid

A

B

C

D

E

F

G

Non-essential amino acids

Asp

3.69

6.59

5.20

3.26

3.50

4.84

5.78

Ser

1.31

2.91

2.53

1.33

1.48

2.16

2.07

Glu

6.43

11.13

9.82

5.72

6.75

8.30

7.86

Pro

3.08

3.32

4.57

2.40

3.35

4.11

1.03

Gly

8.09

17.08

10.02

4.50

7.32

8.43

10.03

Ala

4.10

8.41

5.54

2.69

4.10

4.80

5.02

Cys

0.46

-

0.49

0.52

-

1.17

-

Tyr

0.99

1.65

1.55

1.12

1.06

1.70

1.41

Phe

1.15

1.45

1.78

1.40

1.12

1.99

1.67

Sub-total

29.30

52.54

41.50

22.94

28.68

37.50

34.87

Essential amino acids

Lys

0.64

1.02

1.59

0.38

1.09

1.45

0.92

His

0.17

0.37

0.45

2.82

0.24

0.42

0.40

Arg

3.40

6.60

4.95

1.63

3.45

4.23

4.46

Val

1.59

2.64

2.23

1.09

1.78

2.50

2.43

Met

0.89

1.03

1.40

1.21

0.90

1.49

0.86

Ile

0.76

1.39

1.45

1.93

0.98

1.51

1.64

Leu

1.49

2.64

2.64

1.74

1.75

2.63

2.59

Thr

1.68

3.44

2.68

-

1.89

2.48

2.58

Sub-total

10.62

19.13

17.39

10.80

12.08

16.75

15.88

Total

39.92

71.67

58.89

33.74

40.76

54.25

50.75

A: H. (Metriatyla) scabra; B: H. (Microthele) nobilis; C: H. (Thymiosycia) impatiens; D: H. (Lessonothuria) insignis; E: H. (Lessonothuria) multipilula; F: Actinopyga echinites; G: Thelenota ananas.

Besides the elements mentioned above, vanadium is as high as 12 ppm in the intestine of A. japonicus, which has been used for treating gastrointestinal ulcers (Zhonghua Yaohai, 1993).

The body wall of sea cucumber consists of insoluble collagen, which is similar to that of other herb medicines like "E-jiao", soft-shell turtle collagen and deer-horn collagen. All of these medicines have been used for treating anaemia and as a nutrient supplement of haematogenesis (Liu et al., 1984). Besides higher levels of lysine and arginine, the level of tryptophan is also high in the sea cucumber body wall. This is why the gelatine of sea cucumber is more valuable than other gelatins.

Another characteristic of sea cucumber is the presence of holothurian glucosaminoglycan (HG) and holothurian fucan (HF) in its body wall. It is confirmed that the two mucopolysaccharides (Fan et al., 1979, 1983) are idiographic components of sea cucumber, are found in higher levels in the sea cucumber body and are called "poly-anion elements". Hence, sea cucumber has been nominated as "poly-anion-rich food" that has a physiologically active function, for example, (a) inhibition of some cancers including lung cancer and galactophore cancer (Ma et al., 1982); (b) enforcing immune function (Li et al., 1985; Chen et al., 1987; Sun et al., 1991); (c) anti-aggregation of platelet (Li et al., 1985); and (d) other functions of pharmaceutical value.

Table 4. The amount of inorganic elements of seven species of sea cucumber (ppm).

Element

A

B

C

D

E

F

G

Ba

2.0

6.4

1.7

1

2.9

3.6

2

Co

0.4


0.2

0.4

1.7

0.7

0.4

Cr

10.1

12.9

15.3

9.3

4.4

11.5

10.1

Cu

6.1

1.3

5.9

2

2.5

1.8

6.1

Li

2.0

1.2

1.7

1

1.9

1.4

2

Mn

19.1

2.6

4.1

5.8

11.6

36.1

4.1

Ni

2.9

2.5

5

2.3

1.9

2.1

5

Si

110

12.9

170

11.5

77.6

65

46.6

Sr

616

181

119

57.8

874

64

162

V


0.51

0.51

0.34

0.97

0.72

1.01

Zn

28.6

111

40.9

10.4

9.71

26

70.9

A: H. (Metriatyla) scabra; B: H. (Microthele) nobilis; C: H. (Thymiosycia) impatiens; D: H. (Lessonothuria) insignis; E: H. (Lessonothuria) multipilula; F: Actinopyga echinites; G: Thelenota ananas.

Since the 1990s, sea cucumber has been used as a source of chondroitin sulphate, also known as "sea chondroitin", which is well known for its function to reduce arthritic pain. Recently, an increasing number of commercial products containing sea cucumber or its extracts are available in the market place, such as ArthriSea®, SeaCuMAX®, and are being used for treating rheumatoid arthritis, osteoarthritis and ankylosing spondylitis.

The medical efficacy of sea cucumber is convincing because of the increasing market demand, and consequently this stimulates the development of both farming and fishing of sea cucumber.

Review of sea cucumber production

According to a recent report (Fishery Weekly, China Ocean Daily; 4 July, 2003), Shandong Province has become the second largest producer of sea cucumber. The total farming area reached 17 000 ha, and the total output from culture will achieve 2 250 tonnes in 2003. This means that the wet weight is about 45 000 to 67 500 tonnes (the ratio of wet vs dry is about 1:20-30 depending on the salt level and processing methods). The output in Shandong Province accounts for about one third of national production this year. The largest producer of farmed sea cucumber is in Liaoning Province. According to estimates, the total area of sea cucumber farming will reach about 51 000 ha and the total output will reach 6 750 tonnes (dry weight), equivalent to 135 000 to 202 500 tonnes of fresh weight.

Prior to 2001, the output or landing volume of sea cucumbers was included in other aquatic products in the Annual Report of Fisheries, implying that these products accounted for a small share of the total fishery production. Since then the official statistics categorise sea cucumber separately (Table 5).

In Table 5, farmed sea cucumber is represented by only one species, Apostichopus japonicus, but the wild species include Thelenota ananas (Prickly redfish), Holothuria nobilis (black teatfish), Holothuria scabra (sandfish), Actinopyga mauritiana (surf redfish), Bohadschia argus (Tigerfish), Stichopus hermanni (Squarefish), Stichopus chlononotus (greenfish) in Hainan and Guangdong Provinces (Li, 1990), Apostichopus japonicus (Prickly-fish) in Liaoning and Shandong Provinces and Acaudina leucoprocta, Mensamaria intercedens and others in Zhejiang and Fujian Provinces.

Table 5. The output of sea cucumber in 2001 and 2002 (Annual Report of Fisheries).

Zone and Provinces

Output of sea cucumber (kg)

2001

2002

  Farming Capture Farming Capture

Hebei

1 000




Liaoning

3 837 000

230 000

4 021 000

390 000

Shandong

1 253 000

102 000

1 844 300

46 000

Fujian

-

14 000

-

28 000

Guangdong

-

340

-

1 232

Hainan

-

12 100

-

5 000

Sub-total

5 091 000

358 440

5 865 300

470 232

Total

5 449 440

6 335 532

There is an indication that the output from aquaculture may be a little higher than that of official statistics as many farmers sell their products directly to restaurants and consumers in live form and semi-processed products (Figure 1)., It is popular to eat raw sea cucumber with vinegar or as a steamed product, particularly in the Shandong and Liaoning provinces. Nevertheless, the official figures reflect the developing trends of the contribution of sea cucumber farming and ranching. In fact, sea cucumber farming and ranching has developed such that:

Figure 1. Processed products of sea cucumber, Apostichopus j aponicus; left are fully dried products; right are semi-processed products.

Figure 2. A diver armed with heavy-diving facilities collecting sea cucumber.

Capture Methods

Capture methods vary from area to area. In general, there are two methods; (a) SCUBA diving, or (b) heavy-diving facilities (Figure 2), which are used in the northern part of China

In the southern part of China, especially in Hainan Island, fishermen have designed special facilities for harvesting (Li, 1990). Almost all captured sea cucumber are processed into dried products. The processing methods depend on the species and areas. In the northern part of China - Liaoning, Shandong and Hebei - processors use the same processing procedures (Figure 3).

In the southern part of China, the species are different with most of them being larger than A. japonicus. This means that drying is more difficult. In order to preserve the quality, it is common to use burning charcoal to dry the boiled sea cucumber.

Figure 3. Processingprocedures of sea cucumber in northern part of China.

Farming Methods

There are three methods (Jia and Chen, 2001; Chen, 2003) used for farming sea cucumber: 1) pond culture, 2) pen culture, and 3) sea ranching or sometimes called "bottom culture". In view of its lower investment and higher return, bottom culture accounts for 75 % of total area of culture. For example, in Shandong Province, the total culture area is about 17 000 ha, of which 13 000 ha are in the form of bottom culture; pond culture and pen culture cover 1 800 ha and 2 500 ha, respectively. On other hand, many shrimp ponds left over from the 1990s are becoming much in demand. For example, the rent of a hectare of shrimp pond was about US$ 350 per hectare per year before farming sea cucumber. Now it has risen to US$ 1 800 to 2 000, and can even be as high as US$ 9 000 per hectare per year. From this point of view, sea cucumber farming has been lucrative for coastal fishermen. However, the investment has risks considering that about US$ 5 000 to 6 000 are needed for the preparation of a one hectare pond. Nevertheless, the sector has attracted investment from different sources including funds from local authorities.

Pond culture

Farming sea cucumber in ponds is very popular in China. Furthermore, most existing shrimp ponds can be adapted to meet the ecological demands of sea cucumber. The ideal conditions for a pond culture site are: (a) to be near to the low tide mark so that seawater can be fed into the pond by gravity; (b) no pollution; (c) 28-31 salinity; (d) sandy or sandy-muddy bottom; (e) two metres depth or more; (f) 1 to 4 ha pond size; and (g) presence of shelters to protect the cultured organisms against typhoons or strong wave attack.

The sea cucumber (A. japonicus) is benthic and lives on organic debris and small benthic organisms, therefore, providing more substrate is a necessity. The reason is that the substrate can protect the sea cucumber from predators, while benthic organisms attached to the substrate can be used as a food source. Before introducing seawater into ponds, stones (weighing 20-40 kg each) or other non-toxic material like tiles and bricks can be used and are laid in rows or in a pile (Figures 4 and 5). These materials are used to build the "home" for the sea cucumbers.

Figure 4. The layout of stone substrate in sea cucumber ponds; top picture shows the substrate in row form; bottom picture shows the substrate in cone form.

If the stones (or tiles, etc.) are laid down in rows, each row is usually 3 m wide by 1.5 m high. The interval between rows is about 3-4 m. A pile of stones usually has abase of 4-5 m in diameter and 1.5 m high. The volume of stone used for these purposes is around 2 250 m3 per hectare. Figure 5 shows a pond ready for sea cucumber farming.

Figure 5. Ponds ready for farming sea cucumber; the hut in the top figure is for guarding and monitoring and a sluice gate for introducing seawater from the main supply channel; the bottom figure shows a pond ready for use.

Pen culture

As shown in Figure 6, the ponds are located near to the seashore. At high tide, the seawater naturally flows into the pond by the means of gravity; at low tide, the water in the pond is about 80-100 cm in depth. This method saves a great deal of energy that would otherwise be used for pumping water; meanwhile, incoming seawater brings organic debris into the ponds which provide a good feedstuff for the sea cucumber. It is, therefore, a low cost method and is a highly efficient model, but it is confined to a limited area along the coast.

Figure 6. Pen culture model of sea cucumber in Shandong Province.

Figure 7. Sea ranching flowchart of sea cucumber (A. japonicus).

Sea ranching

Due to the high investment cost for the infrastructure and water management needed for the previous culture methods, sea ranching becomes a more reasonable model for farming sea cucumber as it is more akin to "animal husbandry" in the sea. Successful sea ranching of sea cucumber requires that three main criteria are considered: 1) proper site selection, which includes presence of food sources, suitable salinity and temperature ranges, flow rate, and favourable bottom conditions; 2) environmental improvement, especially the provision of shelter for the farmed sea cucumber; and 3) the release of large size seed material (>5 cm in length is desirable for a good return rate). This model is shown in Figure 7.

Sea ranching experiments of sea cucumber were initiated in the 1950s in Hebei Province (Zhang, 1958), and later, research and demonstration projects were conducted in Liaoning Province (Sui and Liao, 1988) and Shandong Province (Zhang and Liu, 1998) in the 1970s. Convincing results from this earlier work indicated that sea ranching is an effective culture method that could additionally help the recovery of wild sea cucumber stocks.

Example 1:

Location:

Gangdong Village, Qingdao.

Historical record of capture:

The highest record was 350 kg/day/fishing boat equipped with heavy-diving facilities in 1958; average output was 150-200 kg/day/boat during the 1950s and 1960s. During the 1970s the output declined to zero.

Experimental duration:

From 1976 to 1980.

Experimental plot:

3 hectares. The plot was separated into 9 sub-plots, where stones (35-40 kg/piece) were added. Total volume of added stone in the plot reached 600 m3.

Restocking seed number:

8 461 and 5 715 sea cucumbers in 1976 and 1977, respectively.

Results:

See Table 6.

Table 6. Collecting record in the experimental plot of sea ranching of sea cucumber (A. japonicus)from 1976 to 1980.

Sampling date

Sampling record
(No. individuals/hour)

Factor increase from base figure

15/01/1976

30

11

11/01/1977

120

4.0

12/01/1978

144

4.8

05/06/1978

54 in aestivation period

1.9

02/11/1978

174

5.8

26/11/1979

300

10.0

08/01/1980

480

16.0

19/11/1980

474

15.8

25/12/1980

426

14.1

Source: (Zhang and Liu, 1998). 1 = The sampling record value of 30 was taken as the basis for comparison.

In 19 81, a tentative capture was conducted. A total of 318 sea cucumbers weighing 5 6.6 kg were collected during one hour. This indicated that the resources had recovered to historic levels.

Example 2:

Location:

Magezhuang Town, Penglai.

Experimental duration:

1984-1988.

Experimental plot:

3.5 hectares. 7 000 m3 of stone blocks and 40 artificial reef made of concrete were added to this plot from 1984 to 1985.

Census before experiment:

Conducted in 1984 and shown in Table 7.

Table 7. Sea Cucumber census before ranching experiment started in 1984 (Zhang and Liu, 1998).

Item

Sampling point

I

II

III

IV

V

VI

Density (individuals/m2)

1.2

1.2

1.0

0.7

1.0

1.2

Mean weight (g/m2)

82.8

89.4

81.1

62.8

80.2

97.8

Distribution by > 85g

35.0

39.5

46.5

42.2

46.5

50.0

B.W*. (%) < 85g

65.0

60.5

53.5

57.8

53.5

50.0

* B. W. = Body Weight.

Juvenile restocking:

Juvenile size: 1-2 cm in length - 0.48 million, 0.50 million and 0.15 million juveniles were stocked in 1984, 1985, and 1986, respectively.

Feeding protocol:

Chicken manure and formulated feed were used for feeding during March to May, and November to December annually.

Ban period for fishing:

From April 1984 to April 1986.

Results:

Results have shown that the distribution density reached 12.9 individuals/m2. Total quantity in the plot was 47 769 kg (about 430 021 individuals). There were 118 256 individuals that had reached marketable size (>150 g/individual). The mean output per hectare reached 273 kg (Table 8).

Table 8. Results of sea cucumber sea ranching experiment (A. japonicus) from 1985-1987.

Sampling site

Sampling date

Distribution density (individual/m2)

Distribution by body weight (%)
Ranges in grams

highest

lowest

mean

1-15

16-55

56-85

86-125

126-175

>176

I

4/1985

23

17

19.4

6.2

72.2

16.5

5.1



4/1986

30

16

23

3.1

47.4

36.9

11.3

1.3


4/1987

15

5

9.5

2.1

42.1

37.9

15.8

2.1


II

4/1985

19

16

17.4

2.3

66.7

20.7

8.0

2.3


III

4/1985

18

11

13.8

1.5

43.1

37.7

13.3

2.9

2.5

4/1986

26

13

19

7.9

55.2

25.7

10.0

1.2


4/1987

14

5

7.7

6.5

70.4

9

10.4

13.9


IV

4/1985

3

0

1.6

1

20

20

13.3

20.0

26.7

4/1986

14

0

5.1


11.8

23.4

37.2

17.6

9.0

4/1987

6

3

4.1


12.2

22

36.6

19.5

9.7

V

4/1986

14

3

7.9


9.9

16.4

24.1

38.9

11.7

4/1987

5

2

3.9


12.8

30.8

46.2

10.2


VI

4/1985

4

1

2.4


14.3

21.4

42.8

21.5


4/1986

26

7

16.1


13.0

27.4

33.5

21.7

2.5

4/1987

9

3

5.2

1.9

15.4

34.6

44.2

3.8


General census in the plot

1988

Mean density: 12.9
individual/m2
Total number in the plot
(3.5 ha): 430 021

Number > 150g (body weight): 118 256 (27.5% of total number)
Mean output: 273 kg (dry weight)/ha

Source: Zhang and Liu, 1998.

The results from the experiments mentioned above confirmed that sea ranching is an efficient model for recovering and increasing the resources and relieve the burden on natural resources. These experimental results provide valuable experience to farmers. In recent years, sea ranching of sea cucumber (A. japonicus) has become a prosperous part of the fisheries sector.

The key to success involves at least three main points: site selection, improving bottom culture conditions and monitoring predators. The ideal conditions for a desirable site are as follows:

Following site selection, it is most important to improve the sea bottom conditions in order to meet the habitat needs of the sea cucumber. As in pond culture, stone blocks are stocked into the selected site 3-5 months prior to the releasing of the juveniles.

Monitoring is a very important task in order to check the viability of the sea cucumber and, especially, to make sure that predators like sea-stars are eradicated. Monitoring should be done twice per month.

Seed production is the limiting factor in aquaculture and sea-ranching. Seed production research began in the 1950s. In the 1980s, a project was supported by the Ministry of Agriculture (MoA) that achieved significant progress in this field. Since then, about 6-8 billion juveniles have been produced in the hatcheries and have been distributed along the coastline of Liaoning, Shandong and Hebei Provinces. Among them, Liaoning Province is in a leading position. The techniques of seed production were presented at the FAO 'Advances on Sea Cucumber Aquaculture and Management' (ASCAM) workshop (see also Shui, 1985, 1988; Zhang and Liu, 1998).

Marketing and trade of sea cucumber in China

As mentioned earlier in the paper, sea cucumber has been considered a tonic food for many years. Native people living in Liaoning and Shandong Provinces consider sea cucumber (A. japonicus) as a delicacy and are prepared to pay high prices for fresh, dried and processed products. As an old saying in Western countries goes, "An apple a day keeps the doctor away", so now there is a new saying in China, "A sea cucumber a day keeps the doctor away". Hence, we can imagine how large the market for the sea cucumber is. The natural resources of A. japonicus have been badly damaged from the 1950s to the 1970s. For example, the output of beche-de-mer (dried sea cucumber) was 130-140 tonnes and 130 tonnes in Shandong and Liaoning Provinces, respectively, in the 1950s. By the 1970s, the landing volume (dried weight) had declined to 30-40 tonnes and 26 tonnes, respectively. Until to the end of 1970s, capture production had dropped to almost zero. The retail prices of beche-de-mer have increased dramatically since the 1980s. In 1960s, one kilogram of beche-de-mer (Apostichopus japonicus) was RMB 18; in the 1980s the price increased to RMB 500 per kilogram, and in the 1990s it reached RMB 600-1 000 per kilogram. At present, the price exceeds RMB 3 000 (about US$ 400) per kilogram.

The soaring price and the benefits obtained by farmers and investors have stimulated the development of the sea cucumber industry of China. Although the total productivity from sea farming and sea ranching has reached more than 6 000 tonnes (dry weight), the consumption is much higher than domestic production can supply, and therefore, imports of beche-de-mer will certainly continue.

In November 2002, during the Twelfth Meeting of the Conference on the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) held in Chile, a special session dealt with the sea cucumber. The report stated: "The Hong Kong Special Administrative Region (Hong Kong SAR) import statistics show an increase from 25 source countries in 1987-1989 to 49 countries that exported beche-de-mer in 2000-2001."

The total trade in holothurians increased substantially in the late 1980s, and by 1995 had reached a global annual volume of over 13 000 tonnes, valued at about US$ 60 million (Jaquemet and Conand, 1999). Beche-de-mer is primarily exported from producer countries to a central market in Hong Kong SAR, Singapore or Chinese Taipei, and

then re-exported to Chinese consumers' worldwide (Conand and Byrne, 1993). Since the 1980s, the economic status of mainland China has entered into a new era. Economic growth has increased the consumption of sea cucumber in both restaurants and private homes. The consumption of seafood, especially luxurious seafood like geoduck, scallop, shrimps, crabs, groupers, shark-fin, as well as sea cucumber is undergoing a rapid rise.

Also mentioned in the same report are statements relating to the pharmaceutical value of sea cucumbers. Since the 1990s, different health foods or functional foods based on sea cucumber have appeared in drug stores, supermarkets as well as retail shops all over China PR. It is likely that the demand for these products will continue.

According to the investigation of Prof Conand, "In 1989, a worldwide catch of 90 000 tonnes was recorded, consisting of about 78 000 tonnes from the South Pacific and SE Asia and 12 000 tonnes from temperate fisheries. Holothurian fisheries have continued to expand, with a total worldwide harvest of 120 000 tonnes by the early 1990s" (Conand, 1997). The author estimates that the tendency will slow down due to the increasing output from aquaculture and sea ranching sector of sea cucumber in China. This year the output from aquaculture and sea ranching will reach 6 750 tonnes equivalent to 135 000 to 202 500 tonnes of wet weight. This figure almost equals the harvest worldwide from capture. That is why the Chinese participants of CITES claimed that "artificially bred" sea cucumbers have almost replaced sea cucumbers caught in the wild.

Issues and prospects in next decade

Based on the general principle and policy of fishery authorities, aquaculture and sea ranching have been considered a priority sector in the fisheries industry. Further development of farming and ranching of sea cucumber will continue particularly as the allure of high profits will fuel investment into the next decade.

Issues

The expanding farming area and increased output will likely induce the outbreak of diseases. In the aquaculture sector, the emergence of infective diseases has caused serious problems since the late 1980s in salmon, shrimp, shellfish and other farmed species. Sea cucumber could be a new victim in the future. Until now, few researchers have dealt with this issue and farmers have not worried about it. The author is concerned that this could pose a real threat to the newly established sector if the expansion continues at this fast rate and does not consider preventative measures.

The development of sea cucumber farming has been in a status of imbalance. As mentioned earlier, there are about 20 species of edible sea cucumber. Besides A. japonicus in the temperate zone, most of edible species are distributed in southern part of China PR, especially in Guangdong and Hainan Provinces. So far there are no farming operations established. Although the commercial value of tropical species is lower than that of A. japonicus, some species like sandfish, white teatfish and black teatfish, do have a high value. These species are threatened if farming and sea ranching options are ignored.

A national conservation zone of A. japonicus has been established in Liaoning Province although many such zones existed at the county and village level in both Liaoning and Shandong Provinces. Hence, the wild resources and biomass of A. japonicus are close to optimal, but the resources of tropical species are not in as good a shape as the temperate species.

The processing methods and the quality standards for the final products need to be improved. In following the Chinese traditional method of processing sea cucumber, not only is the salt level in the final product higher, but valuable components are lost during processing and cooking. Furthermore, some dishonest processors place uncertified products on the market deceiving consumers with regards to the quality of the product purchased. It is necessary, therefore, to develop a new standard.

Prospects

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