80 Fish as feed inputs for aquaculture – Practices, sustainability and implications
preference. They are either used for human consumption (often processed or preserved)
or used for livestock/fish, either directly or through reduction to fishmeal/oil” (Funge-
Smith, Lindebo and Staples, 2005).
From an Asian regional viewpoint, based on use in aquaculture, the following
categorization is considered appropriate:- Trash fish are generally a mix of species of varying sizes, have minimum
commercial value and often are not suitable for human consumption. They often
originate from bycatches. When landed, the fish normally appear mushy and have
an unpleasant odour (Figure 9). In certain instances, even fish that are suitable for
human consumption may become less desirable due to poor capture techniques or
poor handling and are thus used for feeding cultured stocks. - Low-value fish normally consist of a single species (such as scad, trevally
anchovies or sardines). The quality is relatively good and they may be suitable for
human consumption; the flesh is firm and there is no unpleasant odour. These fish
originate from targeted fisheries whose catch is aimed for human consumption
(Figure 10). However, as their price is low, some farmers who raise higher-value
species commonly use these fish as feed for their cultured stock. Also, some
fish farmers actively fish in local waters to obtain this resource for feeding their
cultured stocks, which practice they believe is cost-effective.
The methods of capture of trash fish/low-value fish, the price ranges of the produce
and its usage in selected Asian countries are discussed by Funge-Smith, Lindebo and
Staples (2005). Fish species considered as trash fish/low-value fish vary from country
to country, and the price also varies with usage in a given country. Importantly, not
all trash fish/low-value fish are destined for use as animal feed in one form or another.
A qualitative assessment by Funge-Smith, Lindebo and Staples (2005) indicated that
in countries such as Bangladesh, India and the Philippines, and to a lesser extent in
Thailand and China, a significant proportion is used for human consumption in fresh,
dried and other processed forms. Also in Viet Nam, trash fish/low-value fish are often
used for processing into fish sauce, and in some countries such as Cambodia and
Viet Nam, these fish undergo “household” processing into a “fish powder” that is used
predominantly for poultry feeds at the cottage level (De Silva, 2008).FIGURE 9
Mixed trash fish/low-value fish used in Asian aquaculture and species representations