depuration and in~~ectionlcertification
methods. InMalaysia, it has been estimated
that depuration would add about 10% to
the production costs and at the same time
shorten somewhat the shelf life of cockles
(FA0 1988).
In order to establish mollusc culture
or to diversify the available commodities,
several introductions of exotic mollusc
species have been made into the region
over the past two decades, especially in the
Pacific Islands. This has raised
international concern because of the
danger of introducing new diseases and
parasites. In order to avoid such problems
in the future, introductions are now
controlled much more carefully. Future
proposed transfers will, hopefully, be
subject to international scrutiny under
codes of practice that are gaining wider
acceptance (Turner 1988; Coates 1992).
Thorough appraisal and safe methods for
transfers of molluscs are especially
important for the Pacific Islands, where
the track record of fish and shrimp
aquaculture development is not very
impressive (Uwate 1988). In most of the
island countries, seafood prices are not
high enough to make aquaculture
competitive with capture fisheries.
However, some commodities produced by
cultured molluscs (e.g., pearl and pearl
shell, trochus shell, green snail shell) are
nonperishable, relatively high priced
products with good market potentials.
There is also a considerable interest in the
region in the culture of giant clams, the
technology ofwhich was developed recently
with international inputs (see Munro, this
vol.).
Seaweed Culture
Several species of marine macroalgae
(called somewhat misleadingly seaweeds)
have been consumed by coastal populations
since ancient times in Asia, particularly in
Japan, Korea and China. Cultivation of
the purple laver (Porphyra tenera) started
in Japan as early as the 17th century. As
seaweed consumption and cultivation
remain Asian specialities, aquaculturists
outside the region tend to underestimate
the role and importance of cultured
seaweed production. Aquaculture statistics
are often quoted with the exclusion of
seaweeds, although this commodity group
represented 25% of the total aquaculture
production in the Asia-Pacific region in
1990 (Table 3).
Culture of seaweeds is restricted
geographically even within the Asia-Pacific
region, although during the past decade
several countries outside the traditional
culture areas have introducedit: Indonesia,
the Philippines and Vietnam in Asia; Fiji,
Kiribati and the Federated States of
Micronesia in the Pacific. Despite these
achievements, only ten out of the 34
countriedterritories of the regionreported
commercial seaweed culture in 1990. The
growth of cultured seaweed production
(Fig. 6) shows surges andrecessions, which
indicate marketing rather than
technological constraints. The annual
average growth rate of seaweed culture
between 1975 and 1990 was only 4.2%, the
slowest among the major aquaculture
commodities.
Seaweed production data in Asia-
Pacific region for 1990 are presented in
Table 15. The major producers were China,
Japan, the two Koreas and the Philippines.
The indicator showing the volume of
production per length of coastline (Table
16) demonstrates the intensity of seaweed
culture in relation to the available coastal
resources. China, with 91.7 bkm-l, shows
an outstanding achievement; the
production of the Republic of Korea and
Japan is also impressive (31.2 and 19.9
t.km-l, respectively). The rest of the
countries are below the regional average
of 11.7 bkm-l.
Half the regional cultured seaweed
production in 1990 was kelp (Laminaria