SRI LANKA

Current Status

Although bivalve resources have been reported to be considerable in the coastal waters of Sri Lanka, bivalve culture is still at the experimental stage. At present, the National Aquatic Resources Agency (NARA), partly supported by the International Development Research Centre (IDRC), is the main governmental agency involved in the applied research of mollusc culture in the country.
A considerable number of edible oyster species has been identified by the agency, however research work is mostly concentrated on the large oysters Crassostrea madrasensis and C. belcheri and on the smaller Saccostrea cucullata.
Although this kind of food is not particularly popular among Sri Lankans, increasing numbers of fishing families involved in deep sea fishery turn to bivalves during the monsoon seasons and in some areas during peak tourist seasons.
These protein-rich organisms are usually salted and dried and sold in the areas where the resources are plentiful. An export-orientated industry for some bivalves in some areas of the country has just started (Indrasena and Wanninayake, 1986).
A series of on-going experiments on the culture of the above mentioned oyster species have shown that these organisms can be successfully cultured in numerous locations along the coastal waters of Sri Lanka. With the introduction of culture methods for the Indian large oyster (C. madrasensis) in 1982, this oyster has become particularly popular among people around the culture areas.
No information has been made available on the distribution of natural oyster fisheries in Sri Lanka. It is believed that both C. madrasensis and C. cucullata are found throughout most of the Island's coasts. According to the limited information available important oyster grounds and culture areas occur in Trincomalee Bay on the East coast, Kalpitiya on the West coast and in several localities in the Southern Province (Table 9 and Fig. 20).
Oyster production figures in Sri Lanka are not available. It is presumed that the annual landings are relatively low due to the overall lack in popularity of oysters as a food item as well as the non-existent export market.

Culture practices

Relatively little information has been gathered on the spatfall seasons of edible oysters in Sri Lanka. According to a recent publication from NARA, C. madrasensis and C. belcheri spawn throughout the year with two peaks in November-January and June-August (Indrasena and Wanninayake, 1986).
Oyster spatfall has been monitored in a number of different intertidal areas along the coast of Sri Lanka, notably in Trincomalee Bay (north-eastern coast), Tangalle and Mirissa Fisheries Harbours (south coast) and Puttalam and Muttuwaran lagoons (north-western coast). The degree of spatfall varies considerably from area to area, mainly due to the size of the resident oyster population. It has also been suggested that poor collection in some sites may be due to the speed and direction of the water current as well as water turbidity. NARA is currently carrying out studies to determine suitable spatfall sites as well as to determine efficient methods for spatfall forecasting, so that cultches can be timely placed into the selected sites (Mr. T. B. Wanninayake, Pers. comm., 1988).
Various oyster cultches have been tested in Sri Lanka, however desirable results have been achieved using coconut shells and windowpane oyster shells (Placuna placenta). Other cultches that have been tested are bamboo slits, asbestos, and rubber plates. It has been shown that highest numbers of spatfall occur on the surface layers of the water column, usually the upper three metres, particularly for C. madrasensis and C. belcheri.

Problems and constraints

The oyster industry in Sri Lanka is currently facing all the typical constraints of establishing a culture system previously non-existent in the country. Very little information is available on the natural distribution of edible oysters, on spatfall seasons and suitable culture techniques. In addition, the lack of trained personnel is contributing to the slow growth of oyster culture.
Although oysters are gaining popularity among small fishing communities, it is generally a food item not highly accepted.
Culture experiments on C. madrasensis, which are being conducted by NARA, are facing problems due to the limited supply of seed. The above situation is probably due to the lack of experience in seed collection by the personnel involved.

Future plans

Due to the rich resources of bivalves, especially oysters, in certain coastal areas and lagoons of the country, considerable effort is being channelled towards the collection of required biological and environmental information (i.e. culture site selection, culture methods, spat collection timing, etc.).
The technical staff of the National Aquatic Resources Agency is the only group currently active in the field of applied mollusc culture research. The on-going experiments on oyster spat collection and culture carried out by the Agency have produced encouraging results. However further research is required.

Table 9. Distribution and main culture areas of commercially important oyster species in Sri Lanka.

Figure 20: Major oyster farming areas in Sri Lanka.