The present Regional Seafarming Working Paper collects under a single cover four papers dealing with various aspects of bivalve mollusc aquaculture. Information on the biology, culture practices, site selection criteria, harvesting and storage, sanitation and depuration, as well as on the culture economics of major bivalve species is provided.
These selected technical papers were prepared as part of the Mollusc/Shellfish Culture Course of the 7th NACA Training Course for Senior Aquaculturists in Asia and in the Pacific. This 12 month course commenced in March 1988 and was held at the NACA Regional Lead Centre of the Philippines in Tigbauan, Iloilo. Each paper is self-contained, and as such, some repetitions cannot be avoided, particularly in the description of the culture techniques.
The oysters and mussels are the major species dealt by the authors, mainly because in the Asia-Pacific region, species belonging to the above two genera make up for a large proportion of the total bivalve molluscs annual landings.
The aquaculture industry among developing Asian and Pacific countries has been growing considerably within the last decade, particularly in the mollusc culture sector. Asia is 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 metric tonnes respectively, which accounted for 72.6%, 20.5% and 6.1% of the year's total production.
The bivalve groups which are widely harvested from natural fisheries or cultured in the region belong to the families Ostreidae, Mytilidae and Arcidae, and compared to the above, only few gastropods are important, mostly collected from natural fisheries. Among the latter group, abalones are certainly the most important, as they are highly valued as a food item and therefore highly priced.
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.
From a survey conducted by the Regional Seafarming Project in 1988 (Working Paper NACA-SF/WP/88/4 entitled "Status of mollusc culture in selected Asian countries"), 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.
One of the activity of the Regional Seafarming Project aims to help enhance and promote the seafarming industry through the organization of training courses. Up to date seven courses have been implemented, including one on oysters in the Republic of Korea and one on abalones in the Democratic People's Republic of Korea. Programmed for the future, are courses on pearl and scallop culture, clearly indicating the interest of the region to burst its mollusc culture industry.
