Fish as feed inputs for aquaculture: practices, sustainability and implications

Use of wild fish and other aquatic organisms as feed in aquaculture in the Asia-Pacific 105

5.3 Efficacy of use of trash fish/low-value fish in finfish culture
The use of trash fish/low-value fish as feed in aquaculture may have advantages,
particularly for the many small-scale farmers in Asia. One advantage are low cost,
resulting in less problems for farmers’ cash flows, ready availability of feed in areas
where trash fish/low-value fish are caught, perceived and/or real efficiency in feeding,
and the possibility of the farmers themselves being able to procure at least a proportion
of the daily feed requirements. The main disadvantages in using trash fish/low-value
fish are irregularity in supplies and variability in quality, and also higher discharge of
nitrogen and phosphorus from indigestible constituents, such as bone, than from pellet
feeds.

5.4 Use of trash fish/low-value fish in crab and lobster fattening
5.4.1 Crab fattening
Farmed crab production, almost all of which occurs in Asia, has exceeded wild-caught
production. Production has increased from a mere 14 500 tonnes in 2002 to 117 000
tonnes in 2004, the highest growth rate for any of the cultured commodities in the
world. Crab farming is predominantly based on the mangrove crabs such as Pacific
swamp crab (Scylla serrata), purple mud crab (S. tranquebarica) and green mud crab (S.
paramamosain) and swimming crabs (such as Portunus sanguinolentus). Although the
life cycle of the mangrove species has been closed (Quinitio et al., 2001), commercial
hatchery production is still in its infancy (Kathrivel, 2007). Consequently, crab farming
in Asia is primarily a fattening process, and the main food source is trash fish/low-
value fish, often presented by chopping into suitable sizes, depending on the size of
the stock. The main mangrove crab farming countries are Thailand, Myanmar, the

Courtesy of U Hla Win, Myanmar

FIGURE 17

Softshelled crab farm

a. Individual holding facilities b. Trash fish/low-value fish used for feed

c. Preparation of trash fish/low-value fish to be fed