The scope of the assignment was discussed with Dr. Philip Tortell, the Team Leader, and Dr. H. Rabanal, Aquaculture Consultant of the South China Sea Fisheries Development and Coordinating Programme in Manila. Consultations were made with key personnel of the Directorate General of Fisheries (DGF) on the implementation of the project. Information on previous and present works on shellfish was gathered from the Marine Fisheries Research Institute (MFRI), the National Institute of Oceanology (NIO) of the National Council of Science and the Bogor Museum. The plan of field surveys was prepared with Messrs. Julius Silaen and Ichsan Santika of the DGF, including all essential equipment and supplies.
Information on the commercial species and nationwide resources of shellfish was gathered from the MFRI, NIO and Bogor Museum. Data on resources for each province were acquired from local DGF personnel, private individuals and fishermen. Meteorological data were supplied by the Meteorological and Geophysical Office of each province. Cooperation from provincial and district level fisheries staff and principal village personnel was particularly noteworthy.
Nineteen sites were surveyed in nine provinces (Figure 1). Table 3 shows a list of important shellfishes collected from each of these sites.
(Fig. 2)
Tanjung Balai of North Sumatra is approximately 160 km southeast of Medan. It is within two-hour drive from Medan during the dry season. Situated 2 km inland from the coast, it is accessible by boat via the Asahan river. Its shoreline runs in a northwest to southeast direction and it is protected by the land mass from strong southwest winds but exposed to moderate northerly and easterly winds.
Its foreshore intertidal mudflat extends more than 2 km from the beachhead forming part of the intertidal area of the northeast coast of Sumatra and extending from the province of Aceh in the north to Lampung in the south. This stretch is fed by three big rivers, viz., the Asahan, the Tanjung Tiram and the Pagurawan rivers.
From the mouth to approximately 1 km up the Asahan river, fishermen collect the clam, Meretrix lyrata. At the time of the survey about a hundred boats were in operation. With one or two fishermen operating each boat, clams are scooped from the river bottom with a long-handled dredge. Collected clams are accumulated on one side of the boat. Dissection of Meretrix samples revealed low condition factor indicating a possible spent state of the animal.
Species of Anadara are collected in both the intertidal and subtidal areas, with a depth ranging from 0 to 5 m. Concentrations of these cockles vary from area to area possibly due to the effect of fishing and/or inherent ecological factors. Cockles are handpicked and dredged either manually or towed by a motorised or wind-driven boat. The most common species are A. inflata, A. granosa, A. modifera and A. indica. Close examination of samples taken from the market showed that these Anadara spp are in matured conditions.
The green mussel, Mytilus viridis, sold in the market, was collected from poles of fish traps set at 4 or more km from the shore. Samples of 7 to 10 cm in shell length showed mature gametes in the gonads and mantle while some were already half spent. Young mussel, 1.2–1.5 cm in shell length was also observed attached to shells and large mussel.
North Sumatra is the biggest cockle producing area in Indonesia, with catches landed mostly in Tanjung Balai, from which it is distributed live to markets in Medan and neighbouring towns. In Tanjung Balai cockles are cooked in freshwater, packed in ice and shipped to a neighbouring town for canning. Some cockles are cooked in brine and dried. An improved motorised sieve is used to separate the meat from the shell after cooking.
In certain sea area with a water depth of 4 m there are thick piles of dead shells. Fishermen collect them by hand dredge for sale to buyers in Tanjung Balai who later convert them to lime for construction purposes.
The tidal range at Tanjung Balai is 3.7 m. Sea water condition was recorded at a station 2 km north from the mouth of the Asahan river. The depth was 1.2 m. The temperature at the surface and bottom were 29°C and 30°C, respectively, while salinity was 27 ppt at both depths. The colour of the water was brown with water transparency of 0.3 m. Wind blew from southeast at 10 km/hour creating 0.3 m waves. Current flowed from northwest to southeast averaging 2 knots. Several shallow fish traps, as well as boats operating with gill nets, could be seen.
(Fig. 3)
Located west of Jakarta, Banten Bay can be reached in two hours drive. It is an open bay exposed to northwesterly, northerly and northeasterly winds coming from the Java Sea. It has a muddy foreshore with mangrove vegetation. The shore water was turbid due to discharges of rivers and wave actions. The gradient of the sea bed slopes gently to the center of the bay.
At Lima Island, approximately 4 km northwest of the MFRI laboratory at Karangantu, the water was clear with transparency of more than 2 m. The island is surrounded with a white sandy beach and coral reefs. A floating raft is set near Lima Island where research on fish culture in cages and green mussel (Mytilus viridis) culture is being conducted by MFRI with the assistance of the Japanese International Cooperation Agency (JICA). Research on mussel includes spat attachment and growth rate, Pinctada martensii spats were seen attached to hanging rope and baskets of mussels.
(Fig. 4)
An open bay facing the Java Sea, the coast of Ketapang Bay has extensive tidal mudflats and receives discharges of rivers flowing through agricultural lands. In this area, the MFRI is undertaking research on the green mussel, Mytilus viridis, at a site approximately 2 km north of Mauk, a coastal village situated southeast of the bay at approximately 28 km west of Jakarta. It is exposed to weather from the northwest, north and northeast quarters. At the time of the survey strong northwest wind was blowing at 30 km per hour creating 1 m high waves and causing damages to mussel plots. Water current flowed from west to east at about 1 km per hour.
There are 3 mussel plots set at 5-m depth of water and spaced out at 200 to 400 m apart. These plots are constructed with bamboos. Synthetic ropes 1-cm diameter are hung as spat collectors while circular baskets are used for the growout of the collected mussels.
Underwater observation at one of the plots revealed a thick attachment of mussels. The bamboos were thickly covered with mussels of 2 cm shell length from the low tide mark to the bottom. These need thinning for better growth.
A bamboo retrieved from an old plot, showed attachment of mussels 4–6 cm in shell length together with fouling organisms including barnacles, algae, oysters, sponges and corals. Diving at nearby fish traps resulted in the collection of some large mussels of 5–8 cm in shell length.
Ketapang is a natural area for mussel culture, but the existing method should be replaced by the floating suspension line which can withstand strong wave actions. The industralisation programme for this area is however expected to become a potential constraint to the future development of mussel cultivation in Ketapang.
(Fig. 5)
Located at approximately 40 km northwest of Jakarta, the Pari Island is a group of three islands at 3-hour sailing distance away from Jakarta.
The main Pari Island is elongatedand aligned in a southwest-northeast direction. The two smaller islands to the west connect with it only during low tide. Coral reefs fringing the islands are about 400 m wide. In the southern parts the seabed is uneven with shallow coral reefs scattered with depressions, some measuring 2-m deep. The northern areas have an even bottom, with intertidal flats exposed during low tide.
The MFRI has a station at Kongsi, the westernmost island.
Three floating fishcages measuring 2 m × 2 m × 2 m for siganid culture, are anchored in front of the station in 2-m depth of water. The substrate comprises white sand and rock with growths of eelgrasses and species of Sargassum, Turbinaria and Padina attached to the corals.
On the western side of the island is a fishpen measuring approximately 40 m × 40 m impounded with polyethylene nettings, over a substrate of coral rocks and white sand. The depth of water is 0.5 m during low tide. Siganids and groupers are being cultured. Eelgrasses, Sargassum and Padina can be seen attached to corals and rocks.
The Faculty of Fisheries of the Agriculture University of Bogor is undertaking research on turtles in the island. Turtles are raised from the egg and kept in small wooden boxes, half-filled with slightly saline water.
The NIO has a station on Pari Island, with a bigger establishment comprising a laboratory building, concrete tanks and employees quarters. It has a radio communication system with its main office in Jakarta. The station undertakes research in fishcage and seaweed culture.
Various shells inhabit the islands, including Tridacna spp (giant clams), Meretrix spp, Tellina spp, Anadara maculosa, Pinctada margaritifera, and Pteria penguin. Univalves such as Conus spp, Murex spp, Cypraea spp, Terebra spp and Mitra spp are also common.
Seawater condition was recorded at Kongsi Island adjacent to the floating fishcages, where the depth of water was 2 m. At the surface and 1-m points, the temperature was recorded at 31°C, and at a 2-m point at 30.5°C. Salinity was 34 ppt at all depths. Water transparency was more 2 m. Westerly winds at 40 km per hour created 1-m waves at the outer reef.
(Fig. 6)
The district of Demak, the biggest clam producing area in Central Java, is approximately 25 km northeast of Semarang. It is within a half-hour driving distance away from the city of Demak located 15 km inland.
Demak has intertidal land areas of about 1 km wide, exposed to strong westerly and northerly winds but protected from easterly and southerly winds by the land mass. The substrate is muddy, while the seabed in the subtidal area slopes gradually for 2 km, at which point the depth of water is 4 m. There are five big rivers at Demak whose outfalls predominate the shore habitats.
Sea conditions were recorded at Desa Moro, a village with a fish landing site located along the Bulan river. At 500 m from the shore of the south side of this river, temperatures were at 34°C, 33.5°C and 33°C for the surface, 1-m point and bottom, respectively. Salinity values were evenly at 34 ppt for these three points. Water transparency reading was 0.7 m, and the depth of water was 1.9 m with a muddy substrate. The height of tide at the time was 0.6 m above datum. The tidal range for the area is 1.1 m.
Desa Bungo, a small village located 2 km inland, has a shell fishery in the estuary of a big river, that also serves as an anchorage point for fishing boats. Shells are handpicked during low tide, and a triangular dredge is also operated either manually or by towing with a boat. Collected shells are relayed to the market in Semarang live with shells or preserved with 1 percent tawas (KAlSO4). Piles of empty shells of Anadara inflata, A. granosa, A. nodifera, Meretrix lyrata, Crassostrea cuculata, Placuna Placenta and a Tellina sp were observed around the villages suggesting that these could be relatively more abundant species in the area.
(Fig. 6)
Jepara, located approximately 60 km north of Semarang, has an uneven shoreline with small bays and estuaries. The site surveyed is a small bay approximately 4 km2, situated north of the Jepara Brackishwater Aquaculture Development Centre, and receiving the outflows of three rivers, viz., the Wiso, Bolongan and Sebembo. A small island, Pulau Panjang, is located about 3 km west. The banks of these rivers are composed with fine black sand, mud and silt while at the centre of the bay and along its south coast, the substrate comprises coral reefs and coralline sand with hard rocks. This tends to show that the influence of riverine discharges has limited effects on the marine environment of this bay. This area is exposed to weather from the westerly quarters. The maximum tidal range is 1.1 m, average daily range is 0.5 m.
Seawater conditions were recorded at two stations. At station 1 approximately 300 m west of the Wiso river, salinity values were 17 ppt at the surface, and 20 ppt at the bottom. Temperature readings were at 31°C for both points. Water transparency reading was 0.3 m. The depth of water was 1.25 m, and the bottom is black sandy mud.
At station 2, located about 1 km from the beach, the depth of water was 3.5 m. Temperatures at the surface, 1-m point and the bottom were uniformly 30°C, while salinity values were also uniform throughout the water column at 28 ppt. Water transparency was at 1.1 m. The tide was 0.55 at the time of survey.
Although experimental oyster culture plots have been set at the south side of the bay adjacent to the Jepara brackishwater centre, the area is considered too shallow for this method of culture. Even short hanging clutches are exposed during ordinary low tide. Further, the white coralline sand and rocky substrate makes it difficult for plots to be set. It is considered that bottom culture should be a better alternative method. In this area, the rock oyster, Crassostrea cuculata, can be found attached to rocks and on the sides of the concrete sluice gates of fishponds.
Examination of bamboo poles from dismantled fishtraps revealed two pieces of the green mussel, Mytilus viridis, measuring 3.1 and 5.7 cm in shell length. These have also heavy attachment of marine growths including barnacles, seaweeds, oysters, sponges and other invertebrates. Clams collected in the area include Anadara granosa, A. inflata, A. nodifera, Meretrix lyrata and Tapes spp.
(Fig. 7)
Located on the east side of the northernmost part of Central Java, the subdistrict of Kecamatan Tayu is more than 100 km northeast of Semarang. The site surveyed is on the eastern shore adjacent to a government demonstration fishpond. The area is protected from westerly winds but exposed to weather from the easterly, northeasterly and southwesterly quarters. Its intertidal mudflat extends approximately 400 m from the beach for the entire coast of Djuana. The mud is soft and thick making it impossible for a man to walk on it. Among numerous rivers draining into the area, the Tayu River forms the largest system. In the inland areas pondfish culture and agricultural farming for paddy and sugar cane are the main activities. A sugar mill is located in the southern part of Djuana.
Clams are found from the subtidal zone down to 5 m deep, including Anadara granosa, A. inflata, A. nodifera, A. pilula, Meretrix lyrata and Musculista senhausia.
Seawater conditions were measured at a station 300 m east of the shore. Water temperatures for the surface and bottom were 33°C and 31°C, respectively. Secchi disc reading was at 0.5 m, while the depth of water was 1.5 m with a muddy bottom.
(Fig. 7)
A coastal town situated next to a small bay at Central Java, Rembang is approximately 120 km northeast of Semarang. The site surveyed is Kota Rembang, with a 400-m wide intertidal mudflat extending from Djuana in the east to Lasem in the west for a distance of approximately 30 km. It is well-protected from strong weather from the west, east and south, while exposed to the northerly quarters. One part of the coast of Rembang receives the outflows of four large rivers.
Seawater conditions were sampled at two stations, located 700 m and 2 km north of Sukohardjo village in Rembang town. At the first station, water temperature on the surface was 32.5°C, while at 1-m point and bottom was 31°C for both depths. Salinity was 35 ppt at all depths. The depth of water was 1.7 m. Transparency reading was 0.9 m. The substrate is sandy mud. At the second station, water temperature at the surface was 31.5°C and at 1-m point and bottom, 30°C. Salinity values for all depths were uniformly at 35 ppt. The depth of water is 4.5 m. Transparency reading was 1.8 m, and the substrate comprises corals and rocks. At the sampling time winds came from the northeast at about 5 km per hour, and the ebbing tide was at 0.5 m. The average tidal range for the area is 1.5 m.
Commercial shellfishes collected in Rembang waters include Anadara granosa, A. inflata, A. nodifera, A. antiquata, A. pilula and a Musculista sp.
(Fig. 8)
Located in the channel between the western end of Madura Island and East Java, Soca village was briefly surveyed. It has a vast intertidal mudflat of approximately 2 km wide and 12 km long extending from Tanjung Tajungan in the south to Bankalan in the north. The substrate comprises fine black sand covered with mud and silt. Situated in the channel, this area is well-protected from the trade winds. Continuous tidal currents flow through the channel at a maximum speed of 3 knots at times. On the Javan side of the channel, there is a high level of industrial activity, which could pose a potential pollution threat to the site.
Shell collecting, an activity second to fishing, is carried out during low tide with the aid of wooden skate board to glide over the soft mudflat. Commercial species of shellfish gathered include Anadara granosa, A. nodifera, A. inflata, A. antiquata, A. pilula, Meretrix lyrata, Placuna placenta, and Tapes spp. Mytilus viridis is also found attached to poles of fish traps.
(Fig. 8)
Kwanyar is located in the south of Madura Island, facing Madura Bay. The foreshore of Kwanyar has a hard rocky shore with fine and coarse white coralline sand. There is an intertidal mudflat extending approximately 500 m from the shore, protected from weather from the north and west but exposed to the south and southeast. The rivers are small and usually dry except during the wet season. Spring water flows out of the island into this area, and provides a source of potable water for the population.
The culture of the oyster, Crassostrea cuculata, has been a long-time engagement of the population. Rocks and coral stones are used as oyster spat collectors set in the intertidal zone of the mudflat at a distance of about 100 m from the shore. The attached spats are allowed to grow to a marketable size in 6 months.
The area has a tidal range of 3 m. At the time of survey, the tide was 1.3 m high, thus covering the oyster beds. At a station 100 m from the shore with a depth of water of 0.5 m, temperatures recorded were at 30°C and 31°C for the surface and bottom, respectively. Transparency reading was 0.3 m and the colour of the sea was brown due to the presence of solids and also planktonic organisms.
The area also produced a number of Anadara spp, a Tapes sp and Meretrix lyrata, all gathered along the intertidal mudflat.
(Fig. 8)
Kenjeran is located east of Surabaya on the northwestern shore of the Madura Strait. It has an extensive intertidal mudflat as wide as 1 km. This is part of the intertidal area ranging from the north of the Madura Strait to the south at Tg. Tambak in Sidoardjo, with a length of about 30 km. The Kenjeran area is exposed to the east and southeast while protected from the north and west. From the shore to about 50 m, a 2–4 cm layer of soft mud covers the sand, beneath which the substrate is black sandy mud inhabitated by various shellfishes.
At the village surveyed, the major activity is fishing with wind-driven craft. Various kinds of fish can be seen being sun-dried on trays. The south side of this village is a fishpond area being developed into a recreation centre similar to that of Ancol in Jakarta. There are also some fishpond areas in the north. Numerous fishing boats were anchored far out in the sea while some were moored on the beach for maintenance.
At the time of survey, the tide was low, women and children were gathering shellfish by hand and also using spatula. They appeared to be experienced in locating the habitats of shellfishes. The majority of the catch was composed of Meretrix lyrata, and species of the genus Anadara appeared to be less abundant.
In deeper areas up to 10 m shellfishes were collected using a dredge (gurit). Sailboats are used in collecting operations undertaken usually early in the morning from 0200 to 0600 hours. Shellfish catches are mainly transported to Surabaya market by middlemen, shucked or with shell.
Empty shells are piled up high in various areas of the village. Judged by this observation, it would appear that the village Kenjeran could have a high production of shellfish. Empty shells are sold for use as an ingredient of poultry feeds and for construction purposes.
Bivalves of commercial importance observed at Kenjeran include Meretrix lyrata, Anadara inflata, A. granosa, A. antiquata, A. nodifera, Mytilus viridis, Placuna placenta, Cardium spp and Tapes spp.
(Fig. 9)
Located on the southwest coast of the Madura Strait, Pasuruan is approximately 60 km southeast of Surabaya. It has an intertidal area extending about 1 km from the shore forming part of the mudflat ranging from the subdistrict of Bangil in the west to Probolinggo in the east. The coast receives the outfalls from a number of rivers, of which the Porong and Delang in Bangil subdistrict are the larger.
The area is protected from adverse weather from the west and south but exposed to the north and east. The intertidal flat comprises black fine sand beneath a 3–10 cm layer of soft brown mud. At extreme low tide, the exposed tidal flat extends seawards to approximately 1 km. The seabed has a gentle gradient and at 1 km beyond the lowest tide mark, the depth of water is only at 2–3 m.
At Semara village of Kraton subdistrict, the major activities are fishing and shell gathering. There were 10 boats specifically used for shell fishing. Shell collectors include women and children, working usually in 1 to 1.4 m depth of water. The collected shells are sorted at sea to species for the genera Meretrix, while other forms are unsorted. These are sold to middlemen immediately upon return to port. Each boat has 10–13 collectors and can gather about 50 kg of shells a day. Some women were seen shucking Meretrix with a knife to cut the mussels before opening the shells to get the meat. Other people were gathering shells by searching the intertidal mudflat during low tide. Dredge towed by sailboat is used in deep areas down to 10 m located northeast of Pasuruan, undertaken mostly during the early morning hours.
The tidal range of the area is 3 m. At the time of survey (1500 hours on Dec. 3) the tide recorded was at 1 m. Seawater conditions were recorded at a station 1.5 km from the shore. The salinity recorded was at 25 ppt, temperature at 32.5°C, and transparency at 0.75 m. The substrate was black sandy mud.
Mytilus viridis was collected at 3 m deep of water attached to bamboo poles of fish traps (bagan) mostly about 3 km from the shore. Its shell length ranges from 3 to 6 cm. Dissection of samples revaled matured gonad, while the larger specimens showed a ripe gonad and gametes in the mantle. Bamboo poles with mussel shells have heavy attachments of barnacles, oysters and other marine invertebrates.
Oysters of the species Crassostrea cuculata was observed attached to mangrove trees at intertidal level, with shell sizes ranging from 3 to 5 cm. The window-pane shell, Placuna placenta, was collected in deeper waters using the dredge for the capture of Anadara spp.
Other commercial species of clams include Anadara inflata, A. granosa, A. antiquata, A. pilula, A. nodifera and various species of Meretrix, Cardium, Tapes, Tellina and Cleone.
(Fig. 9)
Located 30 km east of Pasuruan and south of the Madura Strait, Probolinggo receives the outfalls of numerous small rivers. At Mayanan village, the intertidal flat composed of fine black and coralline sand extends approximately 700 m from the shore. Some portions are covered by a 2–5 cm of soft mud. This is a continuation of that of Pasuruan. In the subtidal area the depth of water goes down gradually to approximately 3 m at 2 km from the beach, with a substrate of black sandy mud.
The tidal range is 3 m, and at the time of survey the height of tide was 1.75 m. At a station, approximately 2 km from the shore, the conditions of seawater were recorded. Water temperature at the surface was at 32°C and at 1-m and 5-m points uniformly at 30°C. Salinity values for all points were at 30 ppt. Water transparency was 2 m and the colour of the water was green. The depth of water at the site was 5 m.
Shell gathering is a minor activity in the area, carried out during low tide. Dredging is not practiced. Diving in a fish coral resulted in the collection of a bunch of Mytilus viridis, ranging from 3 to 11 cm in shell length. Dissection revealed mature gonads with the larger shells having gametes in their mantle.
Shells of commercial quantities include Anadara granosa, A. inflata, A. antiqueta, A. pilula, A. nodifera, Meretrix lyrata, Crassostrea cuculata, a Tapes sp and a Tellina sp.
(Fig. 10)
Labuan Lombok is situated at the eastern coast of Lombok Island, approximately 60 km west of Mataram, the capital of the island. It has a small bay approximately 2 km long and 1 km wide, with a small opening to the north facing the Alas channel. The area is protected from winds from all directions. Current inside the bay is primarily influenced by tidal waters with a range of 2 m.
The site surveyed was the western part of the bay. There is a fish landing pier adjoining a new fish auction building. The wooden pilings and braces of the pier provide attachment surfaces for oysters including Crassostrea cuculata and Ostrea spp measuring from 3 to 7 cm in shell length. on the shore area, various commercially important bivalves were collected comprising Mactra maculata, Tapes tristis, Placuna sella, Amalocardia squamosa and Anadara maculosa.
The intertidal area of the bay extends about 50 m from the shore, with black sand covered by a thin layer of soft mud. To the south, the area widens to about 200 m. A small river drains into the southern part of the bay, while freshwater seepages can be noted along the shore within the intertidal zone.
Seawater condition was recorded at a station in front of the pier. Water temperature was uniformly 31°C and salinity 22 ppt at all points. The depth of water at the end of this pier was 2 m with transparency of 1 m. The tide was beginning to rise. Green oceanic waters were seen entering the bay through tidal transport, and mixing with brown turbid estuarine waters in the south. Another salinity reading of 2 ppt was recorded off the beach at about 150 m south of the first station, primarily due to the predominance of riverine waters during the low tide period.
Two other areas, Labuan Haji and Gumbing Bay, were briefly surveyed in Lombok Island. Labuan Haji is approximately 20 km south of Labuan Lombok with an open coast facing the Alas channel and very limited shore area. Coral reefs protect the shore, but these are on the verge of complete destruction due to the use of corals for the manufacturing of lime for construction purposes. Physical characteristics of this area indicate that it is unfavourable for shellfish farming.
Gumbing Bay is located south of Lombok Island and about 6 km east of Kuta town. Central Lombok has a well-protected bay about 2 km long and 1 km wide. It has a white coralline sandy beach. The only freshwater entering the bay is the runoff of a small creek to its northwest. Large amount of a Gracilaria sp of seaweed attached to corals and rocks, is produced from the northern portion of the bay at 1-m deep of water. This area has also rich growths of eel grasses, Sargassum spp and Padina spp. The presence of these seaweeds and the coralline nature of the bay suggest that it is a potential area for the culture of pearl oysters, including Pinctada margarifera and Pteria penguin which have also been found to be present in adjacent waters.
(Fig. 11)
Bima is a town on the Sumbawa Island with a bay about 25 km long and 5 km wide but becoming only 1 km wide at its northern opening to the Flores sea. The bay is protected from weather from all directions, receiving the outfalls of small rivers. Fishpond and mangrove areas are located south of the bay. The east coast is rocky with black sand, while in the south the substrate is clayey mud.
Bivalves are manually collected in mangrove swamps during low tide, including Anadara granosa, A. pausi, A. granosa, Lutraria maxima, Polymeda coakans and Luca edentula. These are sold to the local market. Oyster of the species Crassostrea cuculata is attached to stones within the intertidal zone.
Seawater conditions were recorded at a station with a water depth of 4 m, adjacent to a fishpond area at the southeastern side of the bay. Salinity was at 17 ppt and temperature at 29°C. Transparency reading was 0.2 m, and the substrate is sticky mud. At the time of sampling the tide was 1 m high and rising. The tidal range for the area is 1.4 m.
Bima is a suitable area for shellfish culture but other inherent factors should also be considered. The small population coupled with increasing shellfish production could create problem of oversupplying the local market. The nearest big market is Bali but it is at present not accessible by sea.
(Fig. 12)
Sape Bay is on the eastern side of Sumbawa Island at approximately 42 km from the town of Bima. The site surveyed was the southwestern part of Sanai Island which is approximately 800 m east of the fishing village of Bugis. A small islet is situated about 300 m southwest creating a small channel with 5 m deep of water. The Sanai Island is rocky, forming a low cliff that drops straight down to the seabed of this channel. White sandy beaches with shallow coral reefs are located 200 m to the northwest and northeast. The area is protected from weather coming from any direction except the southeast.
Seawater conditions were recorded along the channel and salinity was at 35 ppt and temperature at 30°C. Water transparency was at 1 m and the water colour was green. The depth of water was 5 m. Current flow from east to west was at a speed of 1 knot. Shells can be gathered in the southern part of the island where the seabed is rocky with coarse and fine sand and coral formations. Bivalves collected at 1 m deep of water include Anadara maculosa, Pinctada martensii, Pecten spp, Cardium spp, Tapes spp, Atrina sp, Pinna sp and Malleus sp, while the common univalves are Conus spp and Cypraea spp. Common seaweeds include eel grasses and Sargassum spp. Pinctada margaritifera and Pteria penguin have also been previously reported from the island. This can be supported by the presence of the molluscs noted above which are closely associated with these pearl oysters. Ground for Pinctada maxima has been reported to be located in the Sape channel. This pearl oyster thrives best in deeper waters at 20–40 m with fast current.
(Fig. 13)
The sites surveyed were the villages of Oesapa and Oebilo located on the southern portion of Kupang Bay. These are 7 and 25 km respectively, from the town of Kupang, and exposed to strong weather from the west.
Oesapa village has a rocky, white sandy shore. Further out to about 100 m are mangrove trees grown on a hard, sticky clay area measuring about 10 to 20 m wide and running parallel to the shore. Shallow areas further out are limited to 100 to 200 m. Some mangrove trees were dying due to the exposure of their roots resulting from persistent wave action and also sand and rock removal for construction purposes.
Shells are gathered along the edge of the mangrove areas during low tide. Metal sticks were used to dig for shells buried 1–5 cm under the clayey soil. The predominant species is Gafrarium gibbia, while Modiolus auratus and Anadara maculosa and Tellina spp are also common.
At one station the seawater was slightly turbid due to wave action generated by west wind. Along the mangrove area, water temperature was at 28°C and salinity at 22 ppt. At another station approximately 200 m east, water temperature was at 32°C while salinity at 30 ppt. The depth of water was 0.2 m.
The oebilo village site is located two km from the main highway, along ricefields and fishponds. Intertidal mudflats extend to approximately one km from the beach, with hard, clayey soil covered by a 10–20 cm layer of fine black sand presumably brought down by the discharges of the river. Mangrove trees appear to suffer the adverse effects of erosion caused by wave action.
Samples of shells collected along the intertidal zone include Anadara nodifera, A. maculata, Meretrix lyrata, Modiolus auratus, Placuna placenta, Crassostrea cuculata and Tellina spp.
Water temperature was at 29°C and salinity at 2 ppt. Turbid water flowing out of the river covered a wide area of the bay. Wind was blowing from the west generating slight wave action.
(Fig. 14)
Maros is the next town north of Ujung Pandang located in the west coast of South Sulawesi facing the Makassar Channel. It is exposed to strong southwesterly and westerly winds.
The site surveyed is Pajupukang village. It has an intertidal zone that extends to approximately 500 m from the shore. Due to erosion of agricultural lands, the shore areas have thick deposits of mud. The seabed was almost flat with a gentle gradient towards the open sea.
Empty shells of Anadara inflata covered the top layer of the ground of the village. From reports, these were collected from 1975 to 1978, the meat of which was exported to Japan. The majority of these shells has a length from 4 to 6.8 cm. Dredges were used for collecting cockles in areas with a water depth from 1 to 3 m. All shells are white due to exposure to the sun, indicating that the collection of shell was stopped for some time. No newly collected shells could be found, as the villagers are not fond of eating cockles.
Seawater conditions were recorded at about 300 m from the mouth of the Belosi River. The depth is 0.60 m with a muddy substrate. Salinity was at 5 ppt and water temperature at 32°C. The water was very turbid due to the discharges of floodwater.
(Fig. 15)
Banggai Island is in central Sulawesi adjacent to the township of Luwuk. The site surveyed is Lokotoi Bay, situated north of Banggai Island. The bay is approximately 1 km long and 700 m wide at the entrance and devoid of the influence of any major freshwater outfalls. A small island fringed by coral reefs is situated at the mouth of the bay. Open seawater normally enter the bay through the west and move out through the east entrance depending on the direction of water currents in the channel. Shore areas are rocky with white, fine and coarse coralline sand. An outer reef fringes the edge of shore at the bay entrance. The northern portion was deep averaging 25 m. The inner bay was shallow with white sand and patches of corals. Sea urchin and eel grasses were common in clear water areas.
Outside the bay is a channel formed by the Banggai and Peling islands where Pinctada maxima was collected. It has a water depth of 30 to 40 m with strong currents reaching 4 knots at certain time.
The bay is under concession for pearl culture with shore-based facilities located on the southern portion. Nine rafts anchored in 20 m deep of water are used for hanging baskets of pearl oysters. The embedding of nuclei in Pinctada maxima for blister and round pearl is carried out in a floating hut tied next to a raft. Pearl oysters are collected by a diving team operating in adjacent waters of a depth of 20 to 40 m.
Seawater conditions were measured from one raft anchored at the entrance of the bay. The temperature was at 29°C and salinity at 35 ppt. The seawater was clear and baskets of oysters hanging 3 m deep could be seen from the surface.
Spats of Pinctada martensii and Pteria penguin were seen attached to hanging ropes and baskets containing the cultured oyster. These species of oysters can also be used for the culture of pearls.
