Based on the above surveys, a preliminary report on the shellfisheries of Indonesia can be written, describing farming activities, methods of gathering shellfish and pearl culture. The areas surveyed were evaluated based on various factors and four sites were recommended for pilot culture projects.
Gathering of cockles and clams
Picking - On sandy mud intertidal zones, cockles and clams are handpicked during low tide. Clams buried 1–5 cm deep in the mud or sand are gathered by scratching the substrate with either hands or spatula. The collected shells are accumulated in baskets or containers. In some areas, collectors use wooden skates to move over intertidal flats of soft mud. Kneeling on one foot, the collector kicks the mud with his other foot. Clams are picked and placed in a basket carried on the skate.
Wading or diving - In shallow subtidal areas clams are also collected first by locating their presence in the substrate, then to be picked up with the foot or hand by diving. Collectors usually carry a nylon net basket hanging around their neck to hold collected shells.
The culture of shellfish in Indonesia as at present is still in an experimental phase, except for pearl culture using Japanese technology in eastern waters. Experimental culture of the green mussel, Mytilus viridis, is being undertaken by the Marine Fisheries Research Institute in Ketapang Bay, and with the assistance of the Japan International Cooperation Agency (JICA) at Banten Bay in West Java. The rock oyster (Crassostrea cuculata) is being cultured in a limited scale for food at Kwanyan, Bankalan in Madura Island, East Java. The culture of cockles (Anadara spp) is practiced at Ketapang Bay.
Pearl culture
Indonesia has four species of pearl oysters that can be used for the culture of pearls. These are the gold-lip (Pinctada maxima), black-lip (P. margaritifera), winged (Pteria penguin) and a species similar to the Japanese Akoya (P. martensii) oysters.
At present, there are five companies engaged in pearl culture in eastern Indonesia. The main species used is the gold-lip oyster collected by divers using underwater breathing apparatus in areas usually 15 to 40 m in depth. Young and matured oysters are kept live for sale to pearl farms. Oysters are placed in wire or plastic baskets and hung from the raft. After a short period of acclimatisation in the farm, the oysters are ready to be operated for the culture of blister and round pearls.
Dredging
Rake with collecting bag - In shallow subtidal areas cockles and clams are gathered by pulling a rake affixed to a collecting bag. The rake consists of three pieces of bamboo sheaths (each approximately 1 m long and 5 cm wide) nailed together to form a triangle. One side is provided with a series of nails as a rake and nylon net as a collecting bag. On a muddy or sandy substrate, the collector moves backwards pulling this gear, which is lifted up after walking for a few meters. The collected clams are sorted from the mud and placed in a basket hanging around the neck of the collector.
Hand dredge operated from boat - A small hand dredge made of flat steel bar and shaped to form a semi-circle, is operated from boat to gather clams. The straight side is provided with 2 cm long teeth, with a collecting bag of mesh-wire attached to the other end, and a long, 6-m wooden pole as handle. In areas with 1 to 3 m deep of water, a fisherman extends the dredge with his boat anchored as far as possible and pulls it towards him while pressing it down to ensure effective dredging. The collected clams are placed on the boat.
Dredge towed by boat - In subtidal areas from 2 to 10 m in water depth, dredges are towed with a boat. Such a dredge made of arched mesh-wire ranges from one to several metres long and both ends are provided each with a towing rope. It is towed singly or in series of 2 or 3 dredges by a wind-driven or motorised boat. Shells are accumulated on one side of the boat.
The nineteen sites surveyed were evaluated based on the following criteria: ecology of site; size of area for development; accessibility and management; and proximity to market and availability of labour. Table 1 shows an overall evaluation of the sites surveyed. Two areas, Banten Bay in West Java and Lokotoi Bay in Banggai, Central Sulawesi, were not evaluated since these have existing projects. At Banten Bay, research is being conducted by MFRI with the assistance of JICA, while Lokotoi Bay is under concession for pearl culture under a joint venture arrangement.
The success or failure of any seafarming activity in a selected site depends upon the suitability of various factors in its environment setting. Shellfishes are affected by physico-chemical and biological characteristics of the sea, and the measurement of these parameters inherent in a site would entail time series investigations. With the limited survey time available to cover the vastness of the country, only spot readings for some of the more pertinent ecological information including the availability of the local shellfish stock, water current, substrate, exposure to wind and wave action and pollution, have been emphasised.
Sites for the farming of various shellfishes, including the species of Anadara, Mytilus, Crassostrea and Pinctada identified for pilot culture demonstration, should have different ecological requirements which can only be properly assessed through time series investigations.
The following ecological factors are briefly discussed:
Local stock. The availability of local stock of the species selected for culture is of prime importance. The absence of such species necessitates the search for the presence of closely associated species. The presence of abundant local stock of the chosen species, is a strong evidence that the ecological conditions of a selected site are favourable to the development of the area for the cultivation of the species. The introduction of an outside species to an area has not been taken into consideration in our assessment although other ecological factors may appear to be favourable as this would entail the consideration of a multitude of ecological problems.
Water current. Water current is another important factor to be considered in shellfish farming. Being filter feeders, shellfishes thrive best in areas where the availability of food is continuously replenished through the intrusion of water currents and daily tidal water transport. Also, the supply of oxygen required by the animal and the elimination of its metabolic wastes can also be enhanced.
Substrate. The type and nature of substrate determine the methods of culture to be applied. For cockles and clams, since they are grown directly on the seabed, this becomes even more important. Muddy or sandy-mud substrates should be selected and not hard or rocky seabed.
For the culture of species of Mytilus, Crassostrea and Pinctada, the nature of the substrate will determine the method of culture to be applied. Thus, for the construction of bamboo plots a muddy bottom is essential, while floating rafts or suspension lines can be sited over any form of substrate.
Depth of water. The optimal depth of water depends on the requirements of the specific species of shellfish and the method of culture to be applied. Thus, for the culture of Anadara species the preferred areas are those from the zero tide level to four below, while Crassostrea species are better suited in areas exposed during low tide for few minutes or hours.
Mytilus viridis has a wider range of vertical distribution. From experience in the Philippines, Mytilus smaragdinus settles on a 10 m bamboo stake from the low tide mark down to the seabed.
For Pinctada species deeper waters are essential for optimal growth in the production of pearl. In the case of P. maxima an optimal water depth of 30–40 m is required.
Exposure to wind. Sheltered areas well protected from strong winds should be selected. In Indonesia where most areas are below the equator, the prevailing strong winds come from southeast and west. Areas facing west and south are therefore, of low priority. Since Anadara species are cultured on the seabed in shallow areas, wave actions generated by strong winds can be a disadvantage. Culture plots or floating rafts could easily be destroyed by persistent wave actions and also their maintenance cost could be high.
Pollution. A site selected should be relatively free from any form of pollution. Being filter feeders, bivalves are prone to contract microbial organisms including those which are harmful to man. Shellfishes collected from sites near populated areas have high counts of Escherichia coli, an indicator of the possible presence of pathogens. Heavy metals present in industrial effluents are readily uptaken by shellfishes. Oil and gas wells and refineries are also potential sources of hydrocarbons to be uptaken by shellfishes.
Other factors. Other factors for consideration are salinity, temperature, pH and turbidity. The range of salinity tolerance for shellfishes differs from species to species. Anadara species, for example, can tolerate low salinity from 0.5 ppt during low tide to as high as 35 ppt during high tide. Species of Crassostrea are capable of closing their shells for days to avoid fresh water during the flood season, but the same is not true with Mytilus. Pinctada species prefer a consistently high range of salinity, and are readily affected by the lowering of salinity.
Turbid waters with a high load of mud and silt are tolerated by Anadara, but not by Mytilus and Pinctada.
Fluctuations of pH and water temperature are undesirable but these rarely happen even in areas with slow current. High water temperatures can however, affect Crassostrea species when exposed for an extended period during low tide.
The size of a selected area for the siting of a pilot farm must take into account the need for adequate spaces for the subsequent development of private farms.
Accessibility of a site is another essential criterion in site selection. This is to facilitate effective management of operations and also provision of technical extension services. This also reduces operational costs, as well as physical inconveniences of farm personnel.
This refers to the proximity of available market outlets for the disposal of products and the availability of labour to undertake farming activities. These help reduce marketing and also miscellaneous staff overhead costs.
A culture site should preferably have convenient access to populated areas or big cities where there is a demand for the product. If transport is necessary it should be cheap and fast, as shellfish are readily perishable.
The availability of labour sources at or near a selected site is vital to the development of shellfish culture.
Of the nineteen sites surveyed four are selected for the development of pilot culture farms for the cultivation of the commercial species of Anadara, Crassostrea, Mytilus and Pinctada.
(Fig. 2)
The area has a number of potential sites for the farming of Anadara and Mytilus. For the culture of Anadara it has a large, flat muddy substrate between 1 to 3 km from the shore. It has an average depth of 1 m and covering an area of approximately 6 000 ha.
Pasuruan has a wide area for the development of shellfish farming sites. The presence of three commercially important species of shellfish of the genera Anadara, Crassostrea and Mytilus, suggests the need to consider the establishment of a pilot farm in this sheltered area. The presence of rivers that flow into the area is especially favourable to the culture of Anadara. The high rate of water exchange between the area and the Madura channel, is expected to sustain a high level of planktonic food supply, dissolved oxygen and flushing of metabolic wastes of bivalves under culture. Pollution from industries is not a threat. It is accessible by road, while market outlets and labour sources are conveniently located.
Shallow areas with an average water depth of 1 m could be utilised for the culture of Anadara. Plots for Crassostrea and suspension lines for Mytilus could be located at sites of 2 m and 4.5 m of water depth, respectively. The potential area at Pasuruan for shellfish farming development is more than 2 000 ha. This excludes locations off adjacent towns which could also be similarly developed.
(Fig. 10)
Lombok Bay has a population of Crassostrea cuculata that could be utilised for farming. The bay has a potential utilisable area of approximately 100 ha. Being an enclosed area, it is sheltered from adverse wind and wave actions. The tidal range of 2 m should incur considerable tidal water movement within the bay necessary for the feeding and respiration of the shellfish. The depth of water and substrate are suitable for the construction of plots for hanging clutches. This bay is relatively free from pollution in the absence of industrial activities on the island. It is accessible by land transport, while the required labour source and market outlet are also conveniently located.
(Fig. 12)
Sape Bay is a potential area for the culture of pearl oysters, Pinctada martensii, P. margaritifera; and Pteria penguin can be gathered within Sape Bay, while Pinctada maxima is found in the adjacent Sape channel.
The southwestern side of Samai Island is the site proposed for the culture of these oysters. An average depth of 5 m is considered favourable for suspension or bottom culture. Situated inside Sape Bay, the area is sheltered from adverse wave action. Pollution is at present not a problem for lack of industrial activities on the island.
