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II. RESULTS (contd.)

4. Dealers of aquarium giant clams in Japan

4-1. Retailers

This survey was conducted on the retailers who had advertised in three magazines, “1998 Marine Tropical Fish Catalog (published by Seibido-shuppan Co., Ltd.)”, “Marine Aquarist No. 4 (published by MPJ Co., Ltd.)”, and “Tropical Marine Aquarium No. 60 (published by Eriei Co., Ltd.). The number of retailers were 38, 12, and 6 in Kanto, Kansai, and other areas, respectively. Table 5 presents trade of aquarium giant clams at retailers.

In Kanto area, information was obtained from 32 retailers out of 38 retailers (84 %). Of the 32 retailers, 31 retailers (97 %) were experienced in selling giant clams, and at the time of the survey 22 retailers (69 %) had giant clam stock at their shops. The main species traded is T. crocea. Of the 31 retailers, 27 retailers (87 %) handle only T. crocea, 3 retailers handle T. crocea and T. squamosa, and one retailer handles T. crocea, T. squamosa, and T. maxima. The monthly average number of giant clams handled by a retailer is 5 to 6 pieces (one piece or none at 6 retailers; 2 to 6 pieces at 11 retailers; and 10 to 20 pieces at 7 retailers). The retail prices quoted by 15 retailers range between 2,000 and 10,000 yen, mostly between 3,000 and 6,000 yen, per piece. Shell length of T. crocea traded is smaller than 10 cm, mostly between 7 and 8 cm. The small size is preferred because most of the consumers have small aquariums.

One retailer in Kanto area handles about 20 giant clams a month together with other marine organisms. Of marine organisms handled by this retailer, invertebrates, such as giant clams and hard corals, account for about 60 %. Giant clams are shipped directly from fishermen in Okinawa. Only giant clams with brilliant mantle color are traded. The retail prices of T. crocea of about 8 cm SL with metallic mantle color range between 3,000 and 4,000 yen per piece. T. crocea attached on coral rock fetches a price of about 8,000 yen per piece.

Table 5. Trade of aquarium giant clams at retailers in Japan.

AreaRetailer No.(1Dealing of giant clamsT. croceaDealing of other species(2
(Yes or No)
Stock at survey
(Yes or No)
Shell length
Retail price
(x 1,000 yen)
Kanto1Y5 to 6N<103.5 to 5 
3Y3 to 5N5 to 103 to 7 
4Y1 to 2Y5  
5Y<1Y103 to 6 
6Y20Y5 to 102 to 5T.s, T.m
7Y2 to 3Y102 to 4 
8Y2 to 3N3 to 45 
9Y5 to 6Y83 to 10 
12Y5 to 6Y10 T.s
13Y1 to 2Y10  
14Y5Y 5 to 6 
15Y10Y 3 
17Y10N6 to 104 to 6T.s
18Y<1N5 to 7 T.s
19Y10 to 20Y   
20Y1 to 2Y4 to 74.5 to 8 
21Y15 to 20Y7 to 85 to 6 
22Y10 to 20Y 5 
23Y5 to 10N7 to 83 to 8 
26Y5Y 4 to 5 
27Y10Y5 to 8  
28Y10Y<103 to 5 
29Y30 to 50Y   
2Y2N52 to 3T.s
3Y2 to 3N8 to 153 to 10 
4Y2 to 3Y8 to 104 to 6 
5Y2 to 3Y6 to 75.5 
6Y2 to 3N   
7Y10Y8 to 105 to 6T.s
9Y10Y8 to 102 to 4 
10Y10N7 to 84 to 5 
11Y20 to 50Y62 to 7 
Other1Y5Y6 to 72 to 8 
3Y3 to 5Y3 to 103 to 5 
4Y1N103 to 5 
5Y1 to 2Y10  
6Y3Y5 to 66 to 8 

1. Underlined numbers indicate that these retailers also carry on wholesale trade.
2. T.s = T. squamosa; T.m = T. maxima

In Kansai area, information was obtained from 11 retailers out of 12 surveyed (92 %). All of them had experiences in selling giant clams, and at the time of the survey 6 retailers (55 %) were having stocks of giant clams at their shops. All the retailers handle T. crocea, and two of them handle T. squamosa as well. The average number of giant clams monthly handled by a retailer is 3 to 4 pieces (one to 3 pieces by 6 retailers; and 5 to 10 pieces by 2 retailers). The retail prices and the sizes of T. crocea and T. squamosa traded in Kansai area are similar to those in Kanto area.

For other areas, information was obtained from all of the 6 retailers. Of them, 5 were experienced in selling giant clams, and at the time of the survey 4 were maintaining stocks of giant clams at their shops. All the retailers handle only T. crocea of 3 to 10 cm SL. They sell one to 5 pieces monthly, the average being 3 pieces. The retail price ranges between 2,000 and 8,000 yen, mostly between 3,000 and 5,000 yen.

4-2. Wholesalers

In Kanto area, four import/wholesale companies which handled marine aquarium pets were visited and interviewed.

Company A is one of the major aquarium pet import/wholesale companies in Kanto area. Of all aquarium pets handled by this company, marine pets account for 70 % in value. Invertebrates account for 10 % of the marine pets. Giant clams are occasionally mix-loaded with fishes and soft corals shipped from Okinawa. The buying price of T. crocea of 10 cm SL or smaller has dropped to 300 to 500 yen per piece due to a low demand attributed to the recent economic recession.

Company B, also one of the major import/wholesale companies, is involved in both wholesale and retail business. It has one retail shop in central Tokyo and one in an urban area. Of all aquarium pets handled by this company, marine pets account for 25 to 30 % in value. Invertebrates account for 20 to 40 % of the marine pets. Ten to 20 pieces of T. crocea are periodically bought directly from fishermen in Okinawa. The amount of giant clams handled a year is 100 to 150 pieces. The retail price of T. crocea of 8 to 10 cm, ranges from 5,000 to 6,000 yen per piece, depending on mantle color.

Company C is a medium sized import/wholesale company. Of all aquarium pets handled by this company, marine pets account for 20 to 30 % in value. Invertebrates account for about 10 % of the marine pets. Ten to 20 pieces of T. crocea are bought from dealers in Okinawa once or twice a month. The amount of giant clams handled a year is 200 to 400 pieces. The wholesale price of T. crocea is about 1,500 yen per piece and they supply about 150 retailers all over Japan.

Company D is a importing broker of marine aquarium pets, selling pets to six wholesalers, four in Kanto, and one each in Osaka and Fukuoka. In terms of value, invertebrates account for 20 % of all organisms handled by this company. Most of these invertebrates are those listed in CITES II, however, no giant clams have ever been imported yet. This company imports from several countries at a frequency of about 50 times a month. The major dealings are with Indonesia (3 to 4 times a week), the Philippines (twice a week), USA (twice a week), Sri Lanka (once a week), and Kenya (once a week). The amount in one shipment ranges from 10 to 50 cartons. The gross weight of one carton is 15 to 20 kg. The manager of this company expressed an interest in importing giant clams from abroad including the Pacific island countries.

In Kansai area, three import/wholesale companies which handled marine aquarium pets were visited and interviewed.

Company E is one of the major aquarium import/wholesale companies in Kansai area. Of all aquarium pets handled by this company, marine pets account for 10 to 15 %. Invertebrates account for about 20 % of the marine pets. Giant clams are bought together with soft corals and coral base rocks directly from fishermen in Amami-ohshima. On the basis of a stocklist provided by the fishermen, the company places orders directly with them as and when a demand arises from the retailers. On the basis of this, the fishermen send aquarium pets directly to the retailers. The retailers order a maximum 10 to 20 giant clams every time. The wholesale price for T. crocea of 7 to 10 cm SL ranges from 1,500 to 2,000 yen per piece, and with a brilliant mantle color it can fetch as high as 5,000 yen per piece. According to the company, marine pets, especially invertebrates, are preferred to freshwater pets, and giant clams with metallic green mantles, attached to coral rock bases have become popular in recent years.

Company F is a import/wholesale company specializing in marine aquarium pets. This company is known as a pioneer for their dealings with public aquariums, who form 20 % of their customers, the rest being retailers. The percentage of invertebrates among all aquarium pets handled by the company is relatively high, about 30 %. Giant clams are bought mixed with marine fishes from a few fishermen in Okinawa. The quantity of giant clams handled by the company in a year is usually 300 to 400 pieces (maximum of 1,000 pieces). The buying price of T. crocea from the fishermen is 400 to 500 yen per piece. The wholesale price is less than 2,000 yen per piece for giant clams of 8 cm SL and 2,000 to 3,000 yen per piece for those of 12 to 13 cm SL. The company orders giant clams regardless of the mantle color and shell length. About 20 % of the giant clams are with metallic colored mantles. The wholesale prices of both T. squamosa and Hippopus hippopus of 30 to 40 cm SL exceed 5,000 yen per piece. This company is also interested in importing giant clams and other marine organisms.

Company G is a small scale wholesaler/retailer specialized in marine invertebrates. For importing stony corals (order: Scleractinia), this company takes care of the necessary procedures, such as an acquisition of the CITES license. Giant clams are obtained from special dealers in Ishigaki Island. Ten to 50 pieces of giant clams are bought mixed with other marine invertebrates, such as soft corals. Almost all giant clams handled are T. crocea and about 300 to 400 pieces are handled every year. The buying, the wholesale, and the retail prices of T. crocea are about 1,000, about 2,000, and 4,000 to 5,000 yen per piece, respectively.

4-3. Other organizations

(1) Public aquariums

In Japan, there are 65 public aquariums which belong to the Japanese Association of Zoological Gardens and Aquarium, as of 1996. Six species of giant clams, namely T. crocea, T. squamosa, T. maxima, T. derasa, T. gigas, and H. hippopus, have been reared in these aquariums. Table 6 presents the number of giant clams by species reared at each aquarium.

Table 6. Species-specific details of giant clams kept by public aquariums.

T. crocea  9  5  1 15  244370
T. squamosa1115152128  316645
T. maxima  4  3  2  131010 8
T. derasa23   5  5  
T. gigas    21315 9
H. hippopus   4  3  4   21122
Tridacna spp.10 716116  5  3 
Total5734373759  89148  154  
Number of aquariums1112 910 9171518

(Source : Japanese Association of Zoological Gardens and Aquariums)

During the period from 1988 to 1992, about 10 public aquariums were rearing only 34 to 39 pieces of giant clams in total. However, both the number of aquariums and giant clams reared by them increased from 15 to 18 and from 89 to 154, respectively, during the period from 1993 to 1995.

Tokyo Sea Life Park is rearing four T. crocea bought from Okinawa through a wholesaler and five T. maxima collected by itself from Ogasawara Island. These giant clams are placed with other invertebrates, such as soft corals, in display tanks, lit with strong metal halide lamps. These giant clams could survive for more than two years in the tanks.

Okinawa EXPO Aquarium collects their giant clams on their own. It also buys some giant clams from local fishermen. It displays giant clams in a corner fenced with a net fence in a 2,000 m3 tank. Giant clams there could survive only for a few months, the maximum being six. It is suspected that a low light intensity and/or medicines applied to fishes in the same tank cause the mortality. Only two T. squamosa of 30 to 40 cm SL were being displayed in the aquarium at the time of the present survey.

(2) Publishers for aquarium pet magazines

There are three major companies who publish magazines on aquarium pets.

Midori Shobo Co., Ltd. publishes a monthly magazine “Fish Magazine”. The circulation of the magazine is 95,000 copies. M.P.J. Co., Ltd. publishes a monthly magazine “Aqualife”, having a circulation of 120,000 copies. This company also publishes a quarterly magazine mainly covering marine aquarium pets, “Marine Aquarist” which has a circulation of 90,000 copies. Eriei Co., Ltd. publishes a monthly magazine “Tropical Marine Aquarium” specializing on marine aquarium pets. The circulation of the magazine is 42,000 copies. Readers of these magazines are aquarium hobbyists and leisure divers. Majority of the readers are male over 30 years old.

All of these magazines carry articles explaining the methods to rear aquarium pets as well as advertisements of marine pet dealers.

5. Marketability of aquarium giant clams in Japan

5-1. Marketing routes

As the marine aquarium is a rather new hobby in Japan, the market and trade of marine organisms is still in its infancy. There are only few traders in the business and none of them have a clout over the market. The marketing route of marine pet organisms in Japan is shown in Figure 5.

Figure 5

Figure 5. Marketing route for marine aquarium pets in Japan.

The bases of marine aquarium pet trade are Tokyo, Osaka and Fukuoka where major international air ports are located (Figure 6). Sixty percent of marine organisms is imported through Tokyo, 30 % through Osaka and 10 % through Fukuoka. The size of the market is largest in Kanto area accounting for 30 to 40 % of the total trade volume. There are two brokers for marine organism import in Tokyo and one each in Osaka and Fukuoka. About 20 wholesalers purchase marine organisms through these brokers. Besides, about 20 wholesalers import marine organisms directly from suppliers abroad. Retailers also purchase directly from these wholesalers situated in major cities. Recently, wholesalers and retailers dealing in marine invertebrates alone have appeared in the market, though in small numbers. The marketing route of marine organisms will tend to be more specialized and diversified in the future.

Figure 6

Figure 6. Map of Japan.

Figure 7

Figure 7. Marketing route for aquarium giant clams in Japan.

In the case of giant clams that are produced in Okinawa and Amami-ohshima, fishermen themselves or local dealers ship giant clams together with other marine organisms to wholesalers or retailers in places of demand (Figure 7). Wholesalers in such areas do not stock the marine organisms for long time, to avoid the risk, and forward them to retailers within two to three days. To minimize the risk, some wholesalers purchase marine organisms only after receiving the order from retailers.

Wholesalers in Tokyo sell 35 to 50 % of their commodity to retailers in Kanto area. The rest is sold all over Japan, though the percentages for Kyushu, Shikoku, Chugoku areas are low. Some wholesalers in Tokyo cover mainly eastern Japan leaving the markets in western Japan to their related companies in Osaka. On the contrary, wholesalers in Osaka covers mainly western Japan market, selling 50 % of their commodity in Kansai area.

Marine organisms are transported from the wholesalers to retailers mainly by trucks. The maximum transporting time is two days. Marine invertebrates such as soft corals are unable to withstand high temperature during the transportation. Therefore, negligible trade is conducted during the summer time. The marine invertebrates are packed in double layer plastic bags with sea water and oxygen. Usually giant clams are packed individually in small plastic bags. However, when clams are small, five to six of them are packed together in a bag.

5-2. Demand and supply

Due to the economic recession since 1991, the demand for aquarium organisms in Japan has been falling. According to a certain wholesaler, it dropped over the last two years to 40 to 50 % of the highest level recorded. The decline in the demand seems to be smaller for marine organisms than freshwater organisms. Since marine invertebrates, particularly giant clams and corals, are new comers in the aquarium market in Japan, they still have some potential to attract hobbyists.

The number of aquarium hobbyists in Japan is estimated at around 1.2 million, out of which 120,000 to 240,000 people are interested in marine organisms, accounting only for 10 to 20 % of the total. Among them, 24,000 to 48,000, or about 20 %, are estimated to be marine invertebrate hobbyists and form the present market of giant clams in Japan. Assuming each of them buys two pieces of giant clams a year, it can be estimated that the potential demand for giant clams is about 48,000 to 96,000 pieces a year.

The number of aquarium shops who sell marine invertebrates is estimated at 500. Each of them sells 3 to 5 pieces of giant clams per month on average. The estimated total number of giant clams sold by those shops is 18,000 to 30,000 pieces a year. These giant clams are supplied only from Okinawa and Amami-ohshima as mentioned before. Since the potential demand is 48,000 to 96,000 pieces, there is still a deficit of 18,000 to 76,000 pieces a year.

5-3. Price and pricing factors

(1) The present price

As the demand for aquarium giant clam is not so large, a sudden increase in supply will cause a price fall. Therefore, traders intend to supply small number of high quality commodity at high price.

In Okinawa, T. crocea of 8 cm SL are sold at 200 to 300 yen per piece on shore by fishermen to local dealers, who in turn sell the clams at 500 to 1,000 yen to wholesalers in places of demand. The wholesalers in these places sell the clams at 1,500 to 3,000 yen per piece to retailers, and retailers sell finally them at 3,000 to 6,000 yen per piece to the consumers. These prices vary widely depending on species, size, color and traders involved.

Table 7 presents the prices of giant clams produced in Amami-ohsima offered by a wholesaler in Osaka. Table 8 presents retail prices of giant clams produced in Ishigaki Island, offered by the trader who sells marine invertebrates on mail order. This trader distributes a full color catalogue of marine invertebrates which shows prices of giant clams, classified into eight grades of color and four grades of size.

Table 7. Wholesale prices (yen/piece) of giant clams offered by one of the wholesalers.

SpeciesColor pattern of the mantleSize (cm)
2 to 45 to 67 to 1010<
T. croceaBrown500 – 7001,0001,500 – 2,0002,500 – 3,000
Mixed color8001,3001,800 – 2,3002,800 – 3,300
Metallic500 – 7001,5002,000 – 2,5003,000 – 3,500

SpeciesColor patternSize (cm)
10 to 2020 to 3030<
T. squamosaNot specified2,300–3,3004,000–5,5007,000–9,000

Table 8. Retail prices (yen/piece) of giant clams offered by a mail-order company.

SpeciesColor pattern of the mantleSize (cm)
8 to 99 to 1010 to 1212<
T. croceaBrown1,8002,6003,6004,400
Silver-and-green stripes3,6004,8005,8006,800
Blue spots3,9005,2006,0006,800
Green spots4,2005,4006,2007,200
Metallic9,60014,600   18,090   24,600   
T. maximaStandard2,9003,8004,7005,200
Blue stripes9,60014,600   18,800   24,600   
Metallic spots9,60014,600   18,800   24,600  

SpeciesColor of the shellsSize (cm)
20 to 2323 to 2626 to 3030<
T. squamosaWhitish shells5,8007,80012,80014,800
Clear color shells6,8008,20014,80016,800

SpeciesColor patternSize (cm)
15 to 1717 to 2020 to 2525<
H. hippopusNot specified3,2003,6003,9004,600

(2) Species

Most of the giant clams, about 90 %, traded in Japan for aquarium is T. crocea produced in Okinawa and Amami-ohshima. The rest is composed of T. squamosa and small numbers of T. maxima and H. hippopus. T. squamosa attracts hobbyists with its fin-like projections covering the whole shell surface rather than its mantle color. Some hobbyists who have large aquariums want to keep T. squamosa larger than 20 to 30 cm. T. maxima with brilliant mantle color has the same value as the T. crocea with metallic mantle color, though the former species grows larger than the latter.

Since the most important point for hobbyists is mantle color, even T. derasa and T. maxima are found to attract hobbyists if they are brightly colored.

(3) Color and pattern of mantle

Though the color and pattern of mantles are the most important factors that determine the consumer price of giant clams, there seems to be no objective standard for pricing. The mail-order trader in Ishigaki Island sells T. crocea of metallic color at a price 5.2 to 5.6 times higher than that of those with brown mantle (Table 8). In contrast, one wholesaler in Osaka prices clams with beautiful mantle only 1.5 times that of clams with poor color (Table 7).

In the Kingdom of Tonga, cultured T. maxima are classified into three categories of mantle color, namely blue, green and gold, to meet the demand of USA market. Some market standards must be introduced to classify the giant clams on the basis of their value, and ensure supply of high quality clams to hobbyists in Japan.

(4) Size

The aquarium hobbyists in Japan commonly use small aquariums, around 60 cm wide. Therefore, giant clams of less than 10 cm in shell length are most popular in Japanese market. Okinawa does not supply clams smaller than 8 cm SL, because fisheries regulation prohibits the capture of these sizes. The trader in Ishigaki Island sells the giant clams of 12 cm SL or larger, 1.7 to 2.4 times as expensive as those of 8 to 9 cm SL (Table 8).

Most of giant clams supplied from Amami-ohshima, where there is no regulatory size limit, are smaller than 8 cm SL. The wholesale price per piece from Amami-ohshima is 1,500 to 2,500 yen for clams of 7 to 10 cm SL, 1,000 to 1,500 yen for 5 to 6 cm SL and 500 to 800 yen for 2 to 4 cm SL (Table 7). If the clams are attached to the coral base rock (also called live rock), they fetch much higher prices.

(5) Transportation costs

Importing brokers and wholesalers purchase minimum of 100 kg of marine organisms in one shipment to keep the transportation cost per piece the least. Since they purchase only a maximum of 3 kg giant clams in one consignment due to low market demand, they always order other marine organisms together with giant clams. This kind of mix-loading of marine organisms actually is crucial in fixing the retail value of giant clams. Loss of organisms due to damage or death to be kept a minimum and organisms which would not damage the clams while loading, packing and transportation have to be carefully chosen. This pushes the transportation costs considerably.

Marine aquarium organisms are usually traded by cash transaction, on C&F basis. When any loss of organisms occurs during the transportation, it will be compensated by the exporter in the subsequent shipment.

5-4. Competitors of South Pacific giant clams

At present the only competitors to the South Pacific cultured giant clams are those produced in Okinawa and Amami-ohshima. There is a possibility that the South Pacific giant clams are imported to Japan through Hawaiian traders. Table 9 shows prices per piece of the South Pacific giant clams offered by a Hawaiian trader. A New Caledonian trader is selling giant clams by order through Internet. The prices per piece offered by that trader are shown Table 10.

Table 9. The prices of aquarium giant clams offered by a Hawaiian trader.

SpeciesMantle colorSize (shell length)Price per piece
T. maximaBrilliant5cmUS$ 18.40
T. squamosaBrilliant4–5 cmUS$ 10.50
T. squamosaBrilliant6–7 cmUS$ 20.35
T. squamosa   Gold6–7 cmUS$ 9.35 

Table 10. The prices of aquarium giant clams offered by a New Caledonian trader.

SpeciesMantle colorSize (shell length)Price per piece
T. derasa 2.5 inchesUS$ 15.00
T. derasaTiger stripes  3 inchesUS$ 40.00
T. derasa >8 inches US$ 100.00  
T. maxima 1–2 inches   US$ 25.95
T. maxima 2–3 inches   US$ 34.95
T. maximaUltra-color  6–12 inches   US$ 250.00–500.00
T. crocea 3–5 inches   US$ 100.00  
T. squamosa > 3 inchesUS$ 20.00

The main target of the above traders is USA. It will be difficult for them to enter Japanese market as their prices are too high compared to clams of Japanese origin.

It is expected that clams from Southeast Asian countries will become compete with the South Pacific giant clams in future. As Indonesia and the Philippines are exporting stony or soft corals and marine fishes to Japan at present, these two countries will become the main exporters of giant clams. Even now, the Philippines are exporting to Japan some amount of frozen cultured giant clams to be used as food. If Japanese market of aquarium giant clams becomes attractive to them, Philippine traders will eventually export giant clams mixed with soft corals or marine fishes by obtaining CITES license from the government of the Philippines.

5.5. Import procedures in Japan

The exporter of aquarium giant clams should obtain the CITES license issued by the concerned government. The license should certify that the giant clams are artificially bred. The validity of the license is usually for three months.

The procedures for import of aquarium giant clams in Japan has become more complicated by the amendment of import regulation on July 1, 1992 for the organisms included in Appendix II of CITES. Before the amendment the importer needed to have the CITES license only at the time of customs clearance, whereas, at present the importer should have it before the giant clams are shipped to obtain the prior approval. The flow of the import procedures after the cited amendment are shown in Figure 8.

Figure 8

Figure 8. An outline of the Japanese import procedures for aquarium pets included in Appendix II of CITES.

The prior approval is usually obtained within three weeks after the submission of the application. However, since September 1997, the procedures to obtain the prior approval takes longer time in some cases, as Japanese CITES Office (Agricultural and Marine Products Office, International Trade Administration Bureau, Ministry of International Trade and Industry) needs reconfirmation on the CITES license issued by some exporting countries through CITES Headquarters in Geneva, Switzerland. As the CITES Office is controlling very strictly the import of CITES organisms, it is not easy to obtain the prior approval to import aquarium giant clams.

At present there are no signatory countries of the Washington Treaty among the Pacific island countries. However, four of them can export giant clams to Japan since they have government agencies to act as CITES Office (Table 11).

Table 11. Government agencies for CITES in the Pacific island countries.

CountryGovernment Agency for CITES
FijiMinistry of Agriculture, Fisheries and Forests
TongaMinistry of Fisheries
SolomonThe Ministry of Forestry, Environment and Conservation
KiribatiSecretary, Ministry of Environment and Natural Resources Development

6. Characteristics of giant clams as aquarium organisms

Giant clams live in symbiosis with algae called Zooxanthellae. They largely depend on the organic matters produced during photosynthesis performed by the algae as their food. Therefore, giant clam rearing requires stronger lighting than needed for marine fishes. A metal halide lamp is a good light source for giant clam rearing as it is strong and matches natural light. When lighting is not adequate, the symbiotic algae will die, causing the mantle color to fade and finally the mortality of the giant clam.

The attraction of a giant clam is its wide variety in pattern and color of the mantle. This is created by the varying arrangement of color cells under the surface cell layer of the mantle. Since mantle of giant clam is always facing upward, giant clams can only be enjoyed by watching them from the upper side. Therefore, the setting of giant clams within an aquarium needs proper judgment. When a giant clam is attached to the coral base rock, it is easier to arrange them in an attractive way, as they look more natural.

Regular maintenance of water quality is also important for the rearing of giant clams in a reef aquarium. Artificial seawater can be used for giant clam rearing. At least 50 to 80 % of the rearing water should be replaced freshly every month. Only when the aquarium is large in size and equipped with ozonizer and protein skimmer, the water exchange rate can be reduced to 20 – 30 % bimonthly. Coral base rocks which retain nitrifying bacteria on the surface can also contribute in maintainig high water quality.

Fishes such as Balistidae, Monacanthidae, and Tetraodondidae are not suitable to be kept with giant clams in the same aquarium as they attack clams. Most of the marine invertebrate hobbyists keep fishes such as Pomacentridae and Gobbidae, and invertebrates such as soft corals, shrimps and tube worms together with giant clams.

In general, marine aquarium, particularly a reef aquarium for marine invertebrates, cost much more than freshwater aquarium. One complete unit of a reef aquarium, 120 cm wide, costs at least 500,000 to 600,000 yen. This is one of the reason why the market of marine invertebrates is still small in Japan. However, as the progress in aquarium technology is very fast, small and inexpensive aquariums suitable for marine invertebrates are now available. This will attract new hobbyists and increase the market-share of marine invertebrates.

7. Marine invertebrates other than giant clams

Usually giant clams are not the main items displayed in a reef aquarium. Most of the reef aquarium hobbyists keep only two to three giant clams together with other invertebrates. The main items usually displayed with giant clams are as follows:

7.1. Stony corals (Order Scleractinia)

Stony corals are listed in Appendix II of CITES. As Indonesia is the only country to issue export license, all stony corals traded by wholesalers in Japan are of Indonesian origin. Vietnam will be another source for stony corals in future, as one lot was imported recently from Vietnam with the CITES license issued by Vietnamese government.

In Japan, some prefectures do not have fisheries regulation to prohibit collection of stony corals. Therefore, stony corals collected in such prefectures are traded in Japan, though the amount is very small.

7.2. Coral base rocks

Coral base rocks (also called live rocks) are dead corals covered with live organisms attaching on their surface. As they are corals, their trade is also restricted by CITES even though they are dead. At present all imported coral base rocks traded in Japan from Indonesia. Coral base rocks collected in the Kingdom of Tonga are exported to the USA, but not to Japan. A large amount of coral base rocks collected in Okinawa and Amami-ohshima are also traded within Japan. In Ishigaki Island fishermen utilize coral rocks which have been used as house fences to produce coral base rock. They immerse the rocks in the shallow sea until the rocks are covered with various kinds of organisms. Also they use the coral rocks which are taken from inland areas more than two kilometers from the coast line, since such rocks are not subject to the fisheries regulation.

7.3. Soft corals

Soft corals are not subject to CITES. However, as they are usually attached on the coral base rocks, the soft corals are imported following the CITES procedures. Almost all soft corals traded in Japan are those imported from Indonesia and the Philippines or collected in Okinawa and Amami-ohshima.

7.4 Other invertebrates

The most popular bivalve among Japanese reef aquarium hobbyists is frame scallop, Lima scabra which is mainly imported from the Philippines. Its wholesale price is about 1,200 yen and retails about 4,000 yen per piece. Small gastropods which eat micro-algae propagating on the surface of the glass and rocks are kept mainly for the purpose of cleaning the aquarium. However gastropods are not much appreciated by reef aquarium hobbyist as they often hide under the rocks or adhere on the glass. As a crustacean, white socks, Lysmata debelius, imported from the Philippines are popular in Japan. Its retail price is about 3,500 yen per piece.

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