Status of mollusc culture in selected Asian countries

by

Alessandro Lovatelli *

INTRODUCTION

The aquaculture industry among developing Asian and Pacific countries (ie excluding Australia, New Zealand and Japan) has been growing faster than any other food commodity group. Figure 1 presents the production outputs for beef/veal, chicken, aquaculture, pig meat and total fisheries from 1977 to 1987 (RAPA, 1988). From the latest available data, the average annual growth rate of the aquaculture sector during the above period was 15.1% compared to 8.9% for pig meat, 7.1% for chicken and 4.0% for both beef/veal and total fisheries.

Mollusc culture in particular has been steadily increasing in the last few years. Figure 2 shows the total world landings (ie. capture and culture) of molluscs from 1980 (3,603,426 MT) to 1986 (4,524,929 MT) with and average annual growth rate of about 3.95% (FAO 1988).
In the mollusc fishery sector the landings from aquaculture activities are known to be high. Figure 3 shows the 1985 mollusc landings from both the capture and culture fishery. Over 2.8 million metric tons mollusc were cultured in 1985 which accounted for over 65.5% of the year's total production (4,399,371 MT). Molluscs are cultured in numerous countries in both northern and southern hemispheres. However, culture activities have extensively developed in the Asian region, particularly in East and Southeast Asia. Figure 4 shows the 1985 mollusc aquaculture production by continent. Asia is far the most important continent in the world in terms of mollusc landings from culture practices followed by Europe and North America. The landings for the three continents in 1985 were 2,094,913, 591,476 and 176,810 MT respectively which accounted for 72.6%, 20.5% and 6.1% of the year's total production. Mollusc culture output in Oceania in the same year amounted to 20,511 MT or 0.7% of the world's culture output. Table 1 shows the major mollusc producing countries in each continent.

* Bivalve expert, Associate Professional Officer, Seafarming Development and Demonstration Project RAS/86/024, Network of Aquaculture Centres in Asia, Bangkok, Thailand.

Figure 1. Total production of meat/fish commodities from 1977 to 1987 in developing Asian and Pacific countries.

The aquaculture production in Asia in 1985 by major resource group is shown in Figure 5. Finfish and seaweed culture in Asia are the most important groups in terms of landings accounting for 44% and 34% respectively of the year's total aquaculture production. Mollusc production ranks third accounting for 20% of the total aquaculture output in 1985.

Table 2 shows the occurrence of major groups of bivalves and gastropods in selected Asian countries. The bivalve groups which are widely harvested from natural fisheries or cultured in the region belong to the families Ostreidae, Mytilidae and Arcidae. Among the oysters two genera predominate, Crassostrea and Saccostrea, whereas only few species belonging to the genus Ostrea are cultured. Depending where in the region, the Crassostrea species of commercial importance are C. rivularis, C. gigas and C. plicatula in northern Asian countries, such as China and Korea. Important subtropical and tropical oyster species include mainly C. belcheri, C. echinata, C. iredalei, C. lugubris, C. madrasensis, Saccostrea cucullata and Ostrea folium. Among the mussels, species belonging to the genera Mytilus and Perna are captured and/or cultured in the region. Species belonging to the Mytilus genus, such as M. edulis and M. crassitesta tend to be temperate water species, in contrast to the more tropical species belonging to the genus Perna, such as P. viridis and P. perna.

Table 2. Occurrence of major groups of bivalves and gastropods in selected Asian countries.

Figure 2. World mollusc landings from 1980 to 1986.

Numerous cockle species are of commercial importance in the Asian region, the most important belonging to the genera Anadara and Arca. One species of major importance is A. granosa or blood cockle which is extensively cultured from southern Korea to Malaysia. Numerous other species are of commercial importance in the region. Among these, several species of clams, scallop and pearl oyster are of great importance. Among the clams, important genera are Meretrix, Paphia, Mactra, Venerupis, Donax and several others. Three genera of scallop predominate in the region: Pactinopecten, Chlamys and Amusium. Among the pearl oysters Pinctada margaritifera, P. maxima and Pteria penguin are of major importance.
Compared to the large number of commercially important bivalve, only few gastropods are important mostly collected from natural fisheries. Among this group, abalones are certainly the most important as they are highly valued as a food item and therefore highly priced. The most important abalone species belong to the genus Haliotis among which H. discus and H. diversicolor predominate. Culture of this gastropods is mainly carried out in temperate Asian countries, mainly in China, Korea and Taiwan, whereas in some tropical countries, such as the Philippines, abalones are exclusively harvested from natural fisheries. The interest in this culture system among Asian tropical countries is growing.

Figure 3. World mollusc landings from capture and culture fisheries in 1985.

Table 3 lists the major species in terms of production quantities in the Asian region. (excluding Japan) along with the 1986 total landings in the region and in the world. The Pacific oyster, C. gigas ranked first in 1986 in terms of quantity landed. Over 322,426 MT was produced mainly in South Korea and Taiwan accounting for 57% of the total world landing of 568,537 MT. The common mussel M. edulis ranks second with 210,659 MT produced mainly in China accounting for 32% of the world landing of 648,343 MT. Some 157,075 MT of the blood cockle A. granosa was produced in 1986, the main producing countries being Malaysia, South Korea, China and Thailand. This species is found only in the region similarly to the green mussel, P. viridis, carpet clam, Paphia undulata, short-necked clam, Venerupis japonica, the cockle Scapharca subcrenata and M. crassitesta. Figure 6 compares the 1986 total world and Asian landing figures of the top fifteen commercially important mollusc species in Asia. Figure 6 illustrates the proportion of the most important mollusc species compared to the total landings in 1986. Among the top species the Pacific oyster C. gigas, the common mussel M. edulis and the blood cockle A. granosa accounted for over 50% of the landings in 1986 (Fig. 7).

Table 3. Major mollusc species in Asia and total world and Asia landings for 1986.

Figure 4. Mollusc aquaculture production by continent in 1985.

The shellfish industry, in particular the shellfish culture sector offers great potential in many countries in Asia and Pacific for increasing domestic consumption and foreign exchange earning from export. In order to realize this potential, developmental programmes have been launched in several countries and some have achieved good results in terms of species cultured, production and export. However, the industry is facing a number of problems and constraints which vary in magnitude and severity according to area and country. The problems affecting the development of this industry may be categorized into three major groups: 1) environmental, 2) biological and 3) social.
Environmental constraints include all those phenomena either caused directly by men or indirectly which induce a deterioration of the mollusc natural environment. Generally, the most evident and rapid factor causing environmental deterioration is pollution from either inorganic or organic substances. Typically the most fertile grounds for both capture and culture mollusc activities are intertidal areas, estuaries and shallow areas along the coastline. Unfortunately, these are the areas which are often more affected seriously by environmental pollution due to land runoff or direct discharge.
Biological constraints are numerous and variable. In mollusc culture one major constraint is the lack of seedlings, as well as the limited suitable culture grounds. Another serious problem which occasionally affects the industry is the occurrence of red tides which renders mollusc inedible due to the accumulation of toxic substances. Other problems may be related to adverse weather conditions which can cause serious losses to both capture and culture fisheries.
Social and institutional constraints which are affecting the industry are also numerous and vary from country to country. The lack of trained personnel in some countries is at present the major problem even though potentially the country has rich natural resources. The limited demand of a commodity, like molluscs in general, due to culture-related preferences as well as health considerations is also a limiting factor in the development of this industry.
Figure 8 lists the major constraints to the development of the mollusc industry and graphically represents the level of importance of each in terms of percentages. (The percentage values were extracted from a survey conducted in fifteen East and Southeast Asian and Pacific countries partly aimed at identifying constraints in the mollusc industry). The limited seed supply appears to be the most serious constraint, followed by the lack of trained personnel and poor quality control. All the listed constraints are interrelated and in order to aid the development of this industry a multi-disciplinary approach needs to be adopted.

Figure 5. Aquaculture production in Asia in 1985 of the major resource groups.

Figure 6. Total world and Asian landings (excluding Japan) of the most important mollusc species in Asia.

Figure 7. Landing percentages of top mollusc species in Asia in 1986.

Figure 8. Major constraints in the mollusc industry and their degree of importance.