Use of wild fish and other aquatic organisms as feed in aquaculture in the Asia-Pacific 103
is rather limited, the most important species being the pangasiid catfishes, walking
catfishes and snakeheads. In all these instances and unlike in most mariculture, trash
fish/low-value fish are used as a major ingredient to prepare, on farm, moist feeds that
are fed to the stock. The greatest use of trash fish/low-value fish in freshwater finfish
culture occurs in pangasiid culture in the Mekong Delta in southern Viet Nam, a sector
that has grown over the last decade and which contributed an annual production of 1.2
million tonnes in 2007. The individual practices are small holdings with ponds, and the
whole sector is estimated to provide employment to 160 000 people, the majority being
in processing, of which over 80 percent are women (Nguyen, 2009; Phan et al., 2009).
In the Mekong Delta, in addition to pangasiid catfish, giant freshwater prawn
(Macrobrachium rosenbergii) and snakehead are also cultured extensively. The types of
feeds used in these culture practices vary widely from region to region. However, in
general, catfish culture is more dependent on farm-made feeds in which trash fish/low-
value fish are a major ingredient (Hung and Huy, 2007). The level of inclusion of trash
fish/low-value fish in farm-made feeds varies widely, ranging from 10 to 30 percent by
wet weight, the other popular ingredients being rice bran and soybean meal. It should
be stressed, however, that over the last two to three years pangasiid catfish culture has
undergone a major shift from farm-made feeds to commercial feed use, driven primarily
by the logistical difficulties of preparing large quantities of daily feeds on farm.
In giant freshwater prawn and snakehead farming in the delta, yields average 1.8 and
1.43 tonnes/ha/year, respectively. The farming practices are almost entirely dependent
on trash fish/low-value fish but also include golden apple snail (Pomacea canaliculata)
as a feed source (Box 7). According to Sinh (2007), the quantity of feed used in these
two farming practices is 39 780 and 25 039 kg/farm/year.
In addition to carps and tilapias, catfishes and snakeheads constitute two important
species groups that are cultured in Asian freshwaters. The catfish species cultured vary
from country to country; for example, the main species cultured in Viet Nam, which has
the greatest catfish farming activity in the region, are the pangasiid catfishes (the sutchi
catfish (Pangasianodon hypophthalmus) and Pangasius bocourti), while catfish culture
in Thailand is based on the hybrid of the bighead catfish (Clarias macrocephalus) and
the North African catfish (C. gariepinus) (Na-Nakorn, Kamonrat and Ngamsiri, 2004).
In the past, in both these culture practices, particularly during grow-out, trash fish/
low-value fish were the main ingredient used for farm-made feeds, and this is still the
case in Viet Nam. However, with the decline in the market value of farmed catfish in
Thailand, the farmers have become more innovative, remaining viable by almost totally
BOX 7
The golden apple snail as feed
The golden apple snail is considered a major invasive species in Asia (Halwart, 1994;
Joshi et al., 2005) and is very common in the Mekong Delta floodplain. Annually, some
20 to 25 tonnes of snail are collected and
used as feed in giant freshwater prawn
farming in the Delta. It is also used in
farm-made feeds in pangasid catfish
culture.Photo: Golden apple snail frequently sold
as fish and prawn feed in the Mekong
Delta floodplain