Malaysia, New Zealand, the Philippines
and Singapore by contributing more than
75% to the total output, while its share is
between 50% and 75% in Indonesia,
Taiwan and Thailand. If landlocked
countries are disregarded, the least
developed countries in this respect are
Bangladesh, India, Cambodia, Myanmar,
Pakistan, Sri Lanka and Vietnam with
less than25% oftheir total output produced
by coastal aquaculture. Out of the 6.7
million t of coastal aquaculture products
in the region, 81% comes from China,
Japan, the two Koreas and Taiwan,
showing a well definedgeographical center
of coastal aquaculture in Asia.
A more detailed analysis based on
indicators showing coastal aquaculture
production per land area and per length of
coastline modulates but does not alter the
above picture (Table 7). It is interesting to
note that the two leading entities (China
and Taiwan) produce more than 100 t of
aquaculture products per every kilometer
of their coastline; production exceeds 50
t.km-l in Thailand and the Republic of
Korea. The regional average is almost 25
thkm-l.
Coastal aquaculture in the major
producing countries is dominated by
seaweeds and molluscs. In 1990, the
proportion of seaweeds was 47% in Asia,
while molluscs contributed 33%. These
ratios are typical for Asia. in the rest ofthe
world, seaweed culture produces only 4%
ofthe total coastal outputwhereas molluscs
contribute as much as 65% to the total.
The share offinfish isll% in Asia and 23%
in the rest of the world, while crustaceans
contribute 9% of the total in Asiaand other
regions.
Despite significant recent advances in
marine fish cage culture and intensive
pond culture of shrimp in most of the
developing countries of the region, tradi-
tional extensive or semi-intensive pond
culture still dominate coastal fish and
shrimp production. Extensive, trapping1
growing ponds producing a mix of fish
(mainly milkfish and mullets) and crusta-
ceans are traditional in the tidal zones of
many Asian countries. The general ten-
dency over the past decade has been to
intensify these and to shift from an uncon-
trolled *polyculturen to monoculture of
shrimp by replacing trapping of wild juve-
niles with stocking. However, in the sec-
ond half of the 1980s, construction of more
intensive shrimp ponds started in several
countries, both in the mangrove belt and
behind it on higher grounds. This profit-
driven development raised serious envi-
ronmental and socioeconomic concerns,
especiallyinTaiwan andThailand (Csavas
1990; Phillips et al., this vol.).
Cage culture of carnivorous marine
fish was practiced mainly in Japan and
Hong Kong in the 1970s, but has
proliferated in parts of Southeast Asia
during the past decade. Simple methods of
cage culture are accepted more easily by
coastal fishing communities than pond
culture of fish or shrimp, for which land
and significant investments are needed.
Expansion of cage culture was especially
spectacular in Thailandin the early l98Os,
but constraints in feed supply and
marketing of the products soon slowed
down further growth. Environmental
problems related to marine cage culture
are not too common in the developing
countries ofAsia due to the limitedvolume
of production. Hazards of overloading the
environment with marine cages, however,
are well documented in Hong Kong and
Japan (Anon. 1990; Davy 1991).
In mollusc and seaweed production,
both on-bottom and off-bottom culture
methods are common, although off-bottom
methods which offer better control over
the culture environment are gaining
ground. Intensification ofseaweed culture
methods is also being pursued by the use
of fertilizers in open coastal waters.
Whereas inland aquaculture in Asia is
dominated by small-scale production, land