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  blue diamond KOREA-US AQUACULTURE -> Main Species->Shellfish->Manila clam
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Manila clam 

◆ Scientific name : Ruditapes philippinarum

◆ Common name : Manila clam (or Japanese carpet shell,
    Littleneck clam, shortneck clam)

◆ Distribution

  In Korea, manila clams are mainly distributed in western and southern coastal areas, including Chungcheongnam-do, Jeollanam-do, Jeollabuk-do and Gyeongsangnam-do.

◆ Ecology & Habitat

  Manila clams are euryhaline species, but they are considered to prefer the salinity 20~30 psu and feed on algal plankton and organic detritus that are carried along the bottom. These clams live in sand, sandy-silt or muddy-gravel bottoms from intertidal zone to several meters depth. These clams spawn from late May to early November, mainly from June to August in the western coastal areas and June to August in the southern coasts in Korea. Gill-filament activities show maximum at water temperature 23.4℃, and stop under 0℃ or over 36℃. Clams (shell length 36~38mm) usually filter the water 0.6~1.6 liter per hour at water temperature 21~24℃. Oxygen consumption of the clams was reduced when the turbidity of the water by suspended particles is higher than 10ppm.

◆ Production and Aquaculture

   Farming grounds in Korea are normally selected sandy-silt or muddy-gravel bottoms from the intertidal zone to 2 meters depth. Licensed area for manila clam farming was totally 5,707ha in 2004 and the main farming regions were Chungcheongnam-do, Jeollanam-do and Jeollabuk-do.

   Recently, total production of manila clams in Korea was 25,325M.T. (in 2002)~40,638M.T.(in 2004), and the aquaculture production in shallow water was 10,652M.T.(in 2002)~27,570M.T.(in 2004). Fishery production in coastal waters of this clam showed steadily reducing trends from 2000 in the range of 12,700M.T.(in 2004)~30000(in 2000).

   

Almost all the seedlings for aquaculture have been caught from wild habitat in Taean, Boryeong, Dangjin and Hongseong in Chungcheongnam-do. Recently, because of reduction in wild seedling resources at natural habitat in Korea, demands for import of foreign juveniles from China and North Korea are being increased. In addition to natural seedling catches, artificial hatchery-based spat producing techniques are already developed by shellfish research center of NFRDI, and development of mass producing techniques in the field (for example in dike pond or tidal flat habitat) still remain as a problem to be solved.

◆ Diseases, Mortality and Prospects

  Mortalities in manila clam farms in fall (mainly October) have been annually reported and the causes of these mortalities were thought as the following; deterioration of health status after summer-spawning activities and diurnal temperature fluctuation in autumn. Therefore, these small scale mortalities have been accepted insignificant to farmers. However, mass mortalities repeatedly have broken out in the spring season (early March to April) almost all over the western coastal farming grounds from 2003. These recent outbreaks by mortality might becaused by severe low temperature in late winter(February), unstable substrata by storms and waves, and Perkinsus.

  Parasitic(eg.), bacterial and viral disease infections, various environmental factors, and ecology and control methods about predatory cohabitant etc. of the tidal flat where naturally spat and juveniles were continually reproduced will be continued by NFRDI.

 The number and area of licensed manila clam farm in 2004.

Province/City

No. of licensed farms

Area(ha)

Busan

3

19

Incheon

13

112

Gyeonggi-do

12

247

Chungcheongnam-do

116

1,445

Jeollabuk-do

150

1,306

Jeollanam-do

182

1,703

Gyeongsangnam-do

130

848

Jeju-do

1

27

Total

607

5,707


Fisheries catches and aquaculture productions of manila clam in Korea

 

2000

2001

2002

2003

2004

Fisheries catch(M.T.)

20,982

19,997

14,673

13,144

12,737

Aquaculture production(M.T.)

17,927

16,433

10,652

27,494

12,737

Total (M.T.)

38,909

36,430

25,325

40,638

40,307


sampled in January sampled in April 2005

Clams artificially hatchery-based produced at Shellfish Research Center of NFRDI. these clams were transplanted to Gochang tidal flat in 2004 to determine whether they can survive or not in the field and sampleded for the examination of growth (Left, sampled in January; Right, sampled in April 2005).


Mass mortalities of manila clams at Gochang farming grounds in the mid-western coast of Korea (March, 2005).


Burrows of mud shrimp, Upogebia major, are suspected as potenial predators on young clams in natural manila clam habitat, Boryeong(left, sand, gravel and shell detritus bottom) and Taean (right, muddy silt bottom).