The Riau Archipelago includes a group of islands located southwest of Singapore at the juncture of the Straits of Malacca and the South China Sea. The two largest islands, Bintan (47 × 50 km) and Batam (23 × 30 km) face the Singapore Strait which is less than 20 km wide.
The climate of the Riau Archipelago is uniformly warm with average air temperatures of 27°C from October through March and 28°C from April through September. Rainfall is heavier during the north monsoon season September-March but some rain occurs during the rest of the year. Although winds are moderately strong during the monsoon season, tropical typhoons do not occur in this area.
The Riau islands are moderately high with hills of 200 to nearly 400 m, but with large areas of mangrove swamps near sea level. The soil is largely mineral with vast areas of red bauxite ore which is removed and shipped overseas. The top soil layer is generally thin, but rubber trees, coconut palms, and various fruits including bananas, pineapple, rambutan are grown. In some places forests are harvested for production of charcoal for shipment to Singapore.
Freshwater is relatively scarce but numerous small streams occur on the larger islands. No freshwater lakes are present but water for Tanjung Pinang is stored in a large reservoir.
The Riau group includes many small islands separated by narrow, usually deep, channels resulting in an extensive shoreline. Since many islands are high, or covered with large mangroves along the shore, many channels and bays are protected from high winds.
Intertidal beaches vary from solid rock to gravel, sandy-silt and silt. A few coral sand beaches occur in areas exposed to waves. Although beaches in channels tend to be steep, large flats exposed at low tide occur in many bays.
Large areas of shallow water, 1–5 m at low tide occur in various areas providing excellent locations for fishtraps and for development of fish farming using pens or mollusc farming using off-bottom methods.
Protected channels 5–15 m deep could well be utilized for the culture of fish in suspended net pens (cages) or for mollusc culture from floating rafts. Strong tidal currents occur in most narrow channels because of the relatively high tidal range (1.7 m at Bintan Island) ensuring adequate dissolved oxygen for fish farming.
The physical and chemical characteristics of inshore waters, as indicated by observations during the present study, are satisfactory for the culture of various warm water species (Annex I). Observed water temperatures which ranged from 26–30°C are ideal for tropical species of oysters, clams, green mussels, penaeid shrimps, freshwater prawns and marine fishes. The small seasonal variation is a special advantage of this area since it permits year round growth of warm water species. In this characteristic, the Riau-Singapore area is equal to Penang and Kuala Lumpur and slightly better than Jakarta, Manila, Bangkok and Colombo. In many other tropical areas such as Calcutta, Hong Kong, Rangoon and Taipei, winter water temperatures drop below 20°C causing a cessation of growth or even mortality of warm water species.
The salinity measured at various places during the present study varied from 26–32 ppt except for one reading of 19 ppt in a river channel of a mangrove swamp. These salinities are satisfactory for most seafarming species and are ideal for oysters, clams and mussels (Annex I).
Observation of pH indicated satisfactory levels of 7.1 to 7.6 in most marine areas and 6.5–6.9 close to the mouths of river channels through mangrove swamps.
Dissolved oxygen levels were 4.5–5.0 ppm which is satisfactory at the observed water temperatures.
Water pollution from domestic or industrial wastes was apparent only in Tanjung Pinang harbour. However, areas near fishing villages that dispose of human wastes directly into the sea could not be used safely for harvesting of molluscs. Silt from the mining of bauxite was observed in several areas including Selat Kijang, the channel between Bintan and Koyan Islands. This silt load would preclude the use of this area for seafarming.
The waters surveyed can be classed as “moderately productive” based on phosphate and nitrate determinations, observation of water colour as an indication of phytoplankton levels, and collection of aquatic species. The water colour observed was uniformly light green. Transparency was low with underwater visibility of 0.5–1.5 m indicating moderately high phytoplankton levels. No clear or blue water areas were observed.
Filter-feeding molluscs were found in all areas but were abundant only in a few. The following species were collected:
|Oysters (6 species)||-||Crassostrea and Saccostrea|
|Clams (5 species)||-||Asaphis, Gafrarium, Arca, Pitar, Atactodea|
Oysters, the most widely distributed molluscs, were approaching or in the spawning stage and a few had recently spawned. All were in moderate condition of fatness except in Tanjung Pinang harbour where the oysters were in excellent condition with thick creamcolored layers of glycogen. This indicates that feeding conditions for molluscs were improved by the discharge of domestic wastes from Tanjung Pinang which supplied additional nutrients.
Nitrate concentrations of 1.55–2.45 milligrams per liter (mg/l) indicated medium to high productivity in channels and bays close to land. Concentrations of 0.43–1.29 mg/l indicated low productivity in open waters further from shore (Annex I).
Phosphate concentrations were consistently low, ranging from less than 0.25 to 0.45 mg/l (Annex I). It appears probable that the land in the Riau area has low fertility because of the thin layer of top soil over mineral subsoil and that the streams carry few nutrients to the sea. This limits phytoplankton production, however food is obviously adequate to sustain a large increase in the population of molluscs and for plankton feeders such as copepods which form an important part of the food chain for fish populations.
Several species of groupers with aquaculture potential occur in the Riau Islands. Serranids of the genera Epinephelus and Plectropomus (kerapu) are caught by commercial fishermen and are sold in Tanjung Pinang or transported directly to Singapore. Both genera are in high demand at high prices.
Four species, E. tauvina, E. malabaricus, P. maculatus and P. leopardus grow faster than other serranids, having an average daily weight gain of about 4 g from a seed size of 125 g. Also these species can withstand crowding to as much as 10 kg/m3 at harvest in cages (Chan, 1981).
Commercially practicable methods have been developed for growing groupers in floating or fixed net pens or cages from seed (100–150 g) to market size (600–900 g) in about four months. Six grouper farms have begun operation in the Riau Islands, three of which were observed during the present study. The most common species in the pens was Plectropomus leopardus.
Several species of siganids (beronang) are captured by Raiu fishermen using traps and nets. Siganus canaliculatus brought 2 000 Rp/kg at Tanjung Pinang in July 1981, but S. quttatus, S. jaru and S. chrysophilos sold for 500 Rp/kg and S. virgattus as low as 200 Rp/kg. During the Chinese New Year holidays in January or February, S. canaliculatus reportedly may bring 7 000 Rp/kg in Singapore.
Siganids have been grown in tanks and cages with mixed results. In some places, high mortalities of large fish have occurred but the causative factors are unknown. One grouper farm at Sembur Island that also grows siganids was observed during the present study. The operator normally buys seed from fishermen and grows them in a nylon netting enclosure, using boiled rice and other scraps for food, and sells them in Singapore during the Chinese New Year holidays. Even with high mortalities, the operator found siganid culture to be profitable.
Snappers of the genus Lutjanus (ikan merah or bambangan), sold for 800 Rp/kg in Tanjung Pinang in July 1981. These can be grown in cages or pens but cannot be stocked at as high a density as for groupers. Also they bring a much lower price than groupers and therefore are less desirable for seafarming (Chan, 1981).
Lates calcarifer (kakap) is caught in small numbers by commercial fishermen and sells for the same price as groupers. This species can be grown in cages but is highly cannibalistic, prone to infection and handling stresses and requires feeding three times a day. Therefore, it is not recommended for seafarming in Riau province at this time (Chan, 1981).
184.108.40.206 Indonesia produces about 50 000 t of Chanos chanos (bandeng) in brackishwater ponds but none in Kepulauan Riau. Because of the absence or scarcity of seed, the farming of milkfish in Riau Islands is not recommended.
Oysters (tiram) are widely distributed in the shallow bays and channels of Kepulauan Riau. Several species were found during the present study.
Crassostrea (Saccostrea) glomerata, the most abundant species, is found attached to the buttress roots of mangroves, and to old fish traps, piers and rocky shores. This is the same species as the mangrove or rock oyster of New Zealand, Australia, New Caledonia, Fiji, Palau and other Pacific Islands. It has also been known in various areas as Crassostrea cucullata, C. commercialis, C. tuberculata and C. amasa. A proposal by Stenzel (1971) would change the generic name to Saccostrea. This oyster has a maximum size of about 4 cm when attached to mangroves high in the intertidal zone, but will grow rapidly to 6–8 cm in length at lower tidal levels. Seafarming methods are well-known but would have to be tested to determine their applicability in the Riau area.
Several areas were found where oyster seeds (spats) could be collected. There is however, a scarcity of old shells suitable for use as spat collectors. It may be necessary therefore, at first to apply methods used in New Zealand and Australia where spats are collected on wooden sticks or asbestos board (Fibrolite) strips.
It has been reported that oysters are abundant on Senayang Island but time did not permit a survey of that area. Local fishermen and their families gather wild oysters there and transport them to Singapore, a 12-hour trip. Retail prices in Singapore are said to be equivalent to 200 Rp/kg oyster. The Bee Hoch Fish Company in Singapore quoted S$11/kg (about 3 300 Rp/kg) in July 26, 1981 for small oysters from the Philippines.
Crassostrea (Saccostrea) mordax, (the pink oyster), a large heavy-shelled oyster which attaches to intertidal rocks, was found only at Menkada Island and in the channel between Asa Besar and Asa Kecil Islands. This species occurs also in Australia, New Caledonia, Fiji, Palau and the Philippines but is abundant only in a few areas. The pink oyster is difficult to open but has excellent flavor. Methods for farming this species have not been developed.
Crassostrea (Saccostrea) iredalei, a large fastgrowing oyster, was found only in Tanjung Pinang harbour on Bintan Island. This is the major species cultivated in more than 1 000 oyster farms in the Philippines. It reaches marketable size of 5–6 cm in 6–8 months and a premium size of 8–9 cm in one year. Only four specimens were collected in Tanjung Pinang harbour suggesting the possibility that this species was introduced from the Philippines during the early 1960's when a government oyster culture project was conducted at this location. If it becomes desirable in the future to introduce oysters from other areas, C. iredalei would be the best species.
Crassostrea (Saccostrea) malabonensis was found only in Tanjung Pinang harbour. This species is widely distributed in the Philippines and is grown with C. iredalei in many private farms. The two specimens collected during this study were 7.8 and 8.5 cm in length, which is equal to the maximum size found in the Philippines. There is a high probability that C. malabonensis was introduced along with C. iredalei during the early 1960's under the government oyster culture project which was located at Tanjung Pinang. Although this species is farmed in the Philippines, it usually is only 3.5–5.0 cm when marketed and therefore sells for lower prices than the larger C. iredalei
Several species of clams (remis) were collected during the study, but none were sufficiently abundant to indicate significant potential for seafarming in Kepulauan Riau. Although blood cockles Anadara granosa are sold in Tanjung Pinang, they reportedly come from Sumatra. The small venerid clam Gafrarium tumidum, which is common in Teluk Bintan, Bintan Island, has excellent market characteristics and might be farmed in the future if culture methods can be developed. This species is harvested in the Philippines and in various Central Pacific Islands. The project for development of shellfish farming in Indonesia proposed by Pagcatipunan, Tortell and Silaen (1981) could provide a sound scientific basis for culture of Anadara and subsequently for species such as Gafrarium tumidum.
Seafarming of the green mussel Perna (Mytilus) viridis (kerang hijau) has excellent potential in North Sumatra, Java and West Nusa Tenggara (Pagcatipunan, Tortell and Silaen, 1981). However, no green mussels were found in Kepulauan Riau during the present study. According to discussions with fishermen and government fisheries personnel no green mussels are present in this area.
Methods for culture of green mussels are well-known and experiments as close as Singapore have indicated good growth, 1 cm/mo, on ropes suspended from rafts. Sustaining populations have been established in the Philippines by transplanting spawning stock to acceptable areas. This suggests the possibility of introducing green mussels to selected places in the Riau Islands which appear to be satisfactory.
Gastropods of the family Strombidae (kerang strombus) are gathered for food in Kepulauan Riau. Specimens about 6 cm in length collected at Tengah Island were Laevistrombus canarium. Methods for culturing the large Caribbean Queen conch Strombus gigas are being developed at Puerto Rico and in the Bahama Islands. Similar methods may be used in the future to increase production of Laevistrombus in Indonesia.
More than 20 000 t of penaeid shrimps (udang) are produced annually in brackishwater farms mainly in Java, Sulawesi and Sumatra, according to DGF's statistics. There is no shrimp farming in Kepulauan Riau but experimental culture of a locally available shrimp Parapenaeopsis spp was attempted by DGF in 1978 but without success. Because of the lack of local seed of the more desirable aquaculture species (Penaeus merguiensis, P. monodon, P. semisulcatus, P. indicus and Metapenaeus spp), marine shrimp farming is not recommended at this time in the Riau Islands. However, marine shrimp farming might be developed here in the future using seed (nauplius) or postlarvae from Jepara or other shrimp hatcheries. The experimental brackishwater ponds built at Tanjung Pinang in 1962 for the earlier shrimp culture project could be used for trial culture of P. merguiensis and other species. These ponds are still usable after nearly 20 years. This indicates that commercial ponds could be built in coastal mangrove swamp in the Riau Islands.
Scylla serrata (kepiting) is common in the Riau Islands and some attempts have been made to grow them in ponds or cages. The major difficulty is the aggressive behaviour and cannibalism of this species which results in high mortality when they are crowded. There is also a problem of seed supply since hatchery techniques have not been developed. Therefore, farming of the mangrove crab cannot be recommended at this time.
Crabs of the genus Portunus (rajungan) are also common in the Kepulauan Riau but farming technology has not been developed. Also these crabs bring a lower market price than mangrove crabs (400–1 000 Rp/kg compared to 1 500–1 700 Rp/kg in Tanjung Pinang). Therefore, seafarming of this crab cannot be recommended at this time.
Seaweeds, especially Eucheuma spinosum (rumput laut) are harvested at various places in Indonesia totalling over 5 000 t, dried weight, in 1978. However, no landings in Kepulauan Riau District were listed in the Fisheries Statistics of Indonesia (1978).
The present study identified several areas in the Riau Islands where seaweeds are harvested by local fishermen, dried and sold at Tanjung Pinang or Singapore. These included Soreh Island, Karas Besar, Telang Besar, and Pangkil Island where 30 persons gather seaweed.
Eucheuma culture was tried by Marine Colloids, Inc. at Telang Besar Island in 1976. After their experiment was terminated, the Research Institute for Marine Fisheries (BPPL) continued experimental seaweed culture for one year but terminated it because growth rate was low (less than 2.5%/day).
Diving surveys at Pangkil Island indicated moderate abundance of E. spinosum. Water analysis and personal observations indicated that this area would be satisfactory for seaweed farming. However, it would be necessary to determine growth rate before recommending private investment.
The present low price for E. spinosum has discouraged the farming and even harvesting of seaweed. However, from an environmental standpoint, many areas in the Riau group appear to be suitable for seaweed culture. This could be especially attractive in remote islands since the product is dried and does not require immediate transport to markets.
About 16 000 t of Tilapia mossambica (mujair) and T. nilotica (ikan nilam) are produced annually in Indonesia, but none in Kepulauan Riau.
The general shortage of freshwater is one limiting factor for culture of tilapia and other freshwater fish species in the Riau Islands. Even the major islands have only a limited supply, mainly in small streams. There are no lakes or freshwater swamps and underground aquifers are reported to be limited.
Water quality might also be a limiting factor as indicated by the low pH (5.7), low alkalinity and hardness (both 20 mg/l) in the Tanjung Pinang reservoir. Generally, tilapia culture is best where waters are alkaline and hardness and alkalinity levels are 100–200 mg/l.
Soil characteristics may also be a problem. The subsoil on Bintan and several other islands observed is red or yellow with high levels of mineral ores such as bauxite with pH of 4.0–5.5. No records could be found of any freshwater ponds that had been built on Bintan Island, therefore, there is no verified information concerning the suitability of this soil for construction of ponds. However, it appears likely that excessive leakage or seepage would occur. Therefore, the development of successful tilapia culture in the Riau Islands appears improbable.
The freshwater or Malaysian prawn, Macrobrachium rosenbergii (udang galah) is a well-established aquaculture species in Southeast Asia and the climate in Indonesia is ideal for its culture. However, the lack of freshwater, indicates that the culture of this species should not be recommended for the Riau Islands. Furthermore, the anticipated problems of pond construction for tilapia culture would also apply to Macrobrachium culture. Low pH also might be a problem even though the low levels of hardness and alkalinity observed in Tanjug Pinang reservoir would be satisfactory.
The islands of the Anambas Archipelago are located in the South China Sea at about 3°N latitude and 106°E longitude. The group includes three large islands (Jemaja, Siantan and Matak), two medium-sized islands (Badjau and Mubur) and numerous small islands. The major villages are Tarempa on Siantan Island and Letong, Padang and Kuala Maras on Jemaja Island.
The climate is typical of the South China Sea with south monsoon winds May through October and north monsoon winds November through April. Monthly averages of maximum daily temperatures at Tarempa range from 33.7°C in May to 27.6°C in January. Minimum daily air temperatures range from a monthly average of 23.6°C in December to 21.4°C in October. Seawater temperatures recorded July 15–19 at various locations were 28–30.5 °C.
The Anambas Islands are generally high with hills over 500 m and with little level land. A narrow coastal plain exists in a few areas, but in most places the coastline is steep and rocky but tree-covered. The principal crop is coconut but various fruits and spices are also grown on the steep hillsides. Some rice is grown in the interior of Jemaja.
Freshwater is relatively scarce but a few small streams occur. There are no freshwater lakes or swamps.
The soil is generally a thin covering over solid rock. The islands apparently are not of sedimentary origin and lack the minerals of the Riau group.
The Anambas group includes many islands separated by narrow, usually deep channels. Numerous bays and coves occur affording some protection from winds and oceanic waves. Many of these are 20–30 m deep, but most have coral heads and fringing reefs extending to within two meters of the surface at low tide.
Shallow areas, some sandy or muddy, occur toward the head of most coastal bays, and a narrow fringe of mangroves are found there. No large mangrove swamps were observed.
The physical and chemical characteristics of the inshore waters as indicated by observations during the present study are satisfactory for the culture of various warm-water species (Annex I). Observed temperatures ranged from 28–30.5°C which is ideal for tropical species of oysters, clams, green mussels, shrimp and marine fishes. The salinity varied from 32–34.5 ppt, pH from 7.1 to 7.7, and dissolved oxygen from 5.0 to 7.0 ppm all of which are satisfactory for seafarming.
The productivity of the waters surveyed can be described as low to moderate. Phosphate which is usually the limiting nutrient for phytoplankton growth was low, ranging from 0.00 to 0.25 mg/l. Nitrate levels were generally low to moderate ranging from 0.73 to 2.31 mg/l. The highest reading which was at Telok Kuala, reflected the contribution of the 600 residents of Kuala Maras village to the enrichment of the water.
Inshore water in coves was green with poor underwater visibility indicating moderate abundance of phytoplankton. This was confirmed by the presence of filter feeding oysters and clams in these areas. Oysters, the most widely collected form, were in good condition of fatness and many had ripe gonads.
Several species of groupers (kerapu) of the genera Epinephelus and Plectropomus are caught by fishermen in the Anambas Islands and sold locally or shipped to Tanjung Pinang and on to Singapore. The recently built fishing base at Tarempa makes up to 20 tons of ice per day which facilitates shipment of fresh fish to these markets.
There has been no market for live juvenile groupers since there are no grouper farms in this area. Therefore, there is no established fishery for small groupers. Most of those caught by handlines are large enough to sell directly for food. It would be necessary to introduce a fishery using fixed traps, lift nets or small portable traps to catch juvenile groupers for rearing to marketable size in cages or pens.
There is a small seasonal fishery for siganids (beronang) in the waters around Siantan and Matak Islands and one fisherman is attempting seafarming at the south end of Matak Island. His enclosure which is about 50 m × 50 m, was built by piling coral rock in two parallel rows and filling the intervening space with small rocks (gravel) from the shore. The location is exposed to the southwest and the walls have been damaged by storms.
The owner has stocked the pen with small siganids and feeds them boiled rice and various food scraps. Growth reportedly is satisfactory but many fish died before reaching marketable size. The owner has now modified that enclosure by adding two more screened openings to improve circulation and believes this will improve survival. So far the farm has not been profitable.
Oysters (tiram) were found in all of the coves observed during the present survey. The following species were collected:
Crassostrea glomerata, the common mangrove or rock oyster was most widely distributed with significant populations at Tarempa village, the DGF Fishing Base, and Telok Baruk on Siantan Island and at Telok Ulu Mangar, the seaplane base, on Matuk Island.
Crassostrea mordax, the pink oyster, was attached to pilings at the DGF Fishing Base, Siantan Island, and to rocks at Telok Ulu Mangar, on Matak Island, and at Telok Tiru and Telok Kuala on Jemaja Island.
Crassostrea echinata, the giant black-rimmed oyster found throughout the Pacific, was collected at the DGF Fishing Base (Siantan Island), Telok Ulu Mangar (Matak Island) and at Telok Kuala (Jemaja Island). This is one of the largest oysters in the world reaching more than 20 cm in length.
Ostrea spp, a small green-shelled oyster which occurs in oceanic waters throughout the Pacific, was found on pilings at the DGF Fishing Base near Tarempa.
Of the species collected only Crassostrea glomerata has aquaculture potential. The large Crassostrea echinata is found in specialized areas, and is seldom abundant enough for a sustained fishery. Also culture methods for this species have not been developed. However, if other areas are found to have significant populations, they might be harvested, dried, and shipped to Hong Kong where large dried oysters are reportedly in high demand.
The seaweed Eucheuma spinosum (rumput laut) was found in one area along the east side of Matak Island and one village has established a small seaweed farm there. The plants are harvested and used for food by boiling to extract the agar and making a gelatin-like product with excellent flavour. There is no fishery for Eucheuma spinosum for extraction of phycocolloids.
The small seaweed farm, which was located in shallow water near a fishtrap consisted of perhaps 50 short wooden stakes driven into the bottom to which the plants were tied. The farm had been established in 1977 and two crops were reportedly produced in one year. However, from the present appearance, the farm is not being maintained. Growth of the large stemmed E. spinosum appeared to be fair to poor.
Only limited areas suitable for seaweed farming were found during the survey.
Although more than 15 species of clams were collected, none have potential for seafarming at this time. No green mussels, conchs or other molluscs suitable for aquaculture were found.
Crustaceans are scarce in the Anambas group although a few spiny lobsters (Panilurus) are reportedly present. Freshwater prawn, Macrobrachium spp was found in streams at the south end of Matak Island and the north end of Siantan Island and might be cultured in small ponds for home use.
Several species of snappers occur in the area but none have aquaculture potential at this time for reasons discussed in Section 2.1.