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

112 Fish as feed inputs for aquaculture – Practices, sustainability and implications

indirectly (as animal food), which contributes to a production of 28 million tonnes

of foodfish for human consumption (Funge-Smith, Lindebo and Staples, 2005; FAO,

2007). FAO (2007) also highlighted the potential competition for trash fish/low-value

fish and suggested that economic considerations will channel this resource to different

usages. However, the results of the present analysis contradict the suggestion that there

will be an increase in the channelling of trash fish/low-value fish into aquaculture;

overall, by 2010 it is predicted that the use of these resources to support an increase in

aquaculture will decrease significantly.

8. IMPACTS OF FISH-BASED FEED INPUTS USED IN ASIA-PACIFIC
   AQUACULTURE
   This section deals briefly with four types of impact: impacts on the environment,
   on wild fish stocks, on human health and on employment and food supplies for the
   poor.

8.1 Environmental impacts

General treatments of environmental impacts on aquaculture include those of Goddard

(1996) and Black (2001). It has been aptly demonstrated that the provision of the

most nutritionally wholesome and digestible diet to a finfish species results in, at

best, an accumulation

of nitrogen in the body

of 28–32 percent and an

average accumulation

of 20–25 percent, the

rest being excreted.

The excessive discharge

of phosphorus

and nitrogen via

undigested faecal

matter in freshwater

aquaculture and of

nitrogen in mariculture,

particularly in

areas where water

replenishment is

inadequate, can lead to

serious environmental

impacts. In the Asia-

Pacific region, such

impacts have been

observed in freshwater

TABLE 20

A summary of the quantities of fish used, directly or indirectly, in aquaculture in the Asia-

Pacific region

Type Current (tonnes) Predicted usage in 2010 (in tonnes)

Low* High* Low High

Reduced forms (fishmeal)

2 388 058

(10 270 894)

• 1 999 866
  (6 999 531)

2 190 729

(7 667 552)

Trash fish/low-value fish 2 465 000 3 882 000 1 890 000 2 795 000

Live fish 675 000 1 012 000 n/a** n/a

*Based on different food conversion efficiencies as indicated in the relevant sections; the live-weight equivalent,

where relevant, is given in parentheses;

**n/a–not attempted

Source: Data derived from Tables 9 and 18 and Figure 20.

BOX 12

Environmental impacts of cage culture

Intensive cage culture operations can lead to exceeding the carrying

capacity of the waterbody, resulting in fish kills when the bottom anoxic

water (resulting from the accumulation of large quantities of nutrients)

is upturned by changed weather conditions. Such regular occurrences

can lead to abandonment of the facility.

Photos: Intensive cage systems in a reservoir in West Java, Indonesia,

and the aftermath of fish kills