Artificial propagation of bivalves:
Techniques and methods
Techniques and methods
| SF/WP/90/3 | October 1990 |
|
Artificial propagation of bivalves: Techniques and methods |
UNDP/FAO REGIONAL SEAFARMING DEVELOPMENT AND
DEMONSTRATION PROJECT (RAS/90/002)
National Inland Fisheries Institute
Kasetsart University Campus
Bangkhen, Bangkok
Thailand
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3.2 Conditioning of broodstock
3.5 Determination of egg numbers
3.6 Placing the egg in culture vessels
3.9.2 Density control and grading
3.12 Preparation of spat for on-growing
3.12.2 Outdoor up-welling system
4.4.1 Ultraviolet light sterilization
5.0 PRINCIPLES AND TECHNIQUES OF PHYTOPLANKTON CULTURE
5.2 Principles of culture growth
5.4 Culture system configuration
Figure No.
1 (A) Sub-sand seawater extraction and (B) surface seawater intake for hatchery use.
2 Home made hatchery sieves and plunger.
6 Preparation of a sperm and/or egg suspension. (Source: Castagna and Kraeuter, 1981).
9 Seawater change of a bivalve larval culture vessel. (Source: Castagna and Kraeuter, 1981).
11 Indoor fibreglass up-welling tank. (A) Seawater reservoir vessel and (B) up-welling tubes.
13 (A) Lantern net and (B) pearl net typically used for the intermediate culture of scallop spat.
14 Land-based nurseries for rearing of juvenile bivalve spat. (Source: CNEXO, 1983).
15 Passive flow (A) and active flow (B) up-flow systems. (Source: Manzi, 1985).
Plate No.
3 Oyster broodstock holding netcage.
4 Oyster broodstock holding pearl nets.
by
Alessandro Lovatelli*
This technical paper was 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.
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 MT, 591,476 MT and 176,810 MT 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 naturally occurring phenomena (e.g. salinity, temperature fluctuations, etc.) or those related to the direct or indirect effects of man's activities. 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.
In order to further expand the mollusc culture industry in the region in the future it will be necessary to solve the problem of limited seed supply. This can be tackled either by artificially producing spat through hatcheries or by improving the techniques aimed at the collection of spat from the wild.
The present Working Paper covers various technological aspects of bivalve artificial propagation. Information on hatchery design and equipment, broodstock management and conditioning, spawning techniques, larval and spat rearing, disease prevention and treatment, as well as on the principles and techniques of phytoplankton culture is provided.
For further detailed information the list of References on page 50 should be consulted. The papers by Manzi (1985) and Castagna and Kraeuter (1981) are particularly relevant.