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

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

accompanied by the increased production of carnivorous finfish (such as salmonids) and

shrimp, there was a concurrent and very significant increase in fishmeal (Figure 11) and

fish oil usage in aquaculture. If this trend continues, aquaculture will become the major

user of these commodities (Tacon, 2004), whose production has levelled off but whose

prices continue to increase (Jackson, 2006; FAO, 2007). Indeed, the price of fishmeal

doubled between 2004 and 2006,

rising to almost US$1 600 per

tonne, freight on board (FOB)

(INFOFISH, 2006).

As shown in Figure 11,

fishmeal usage in poultry farming

has declined very significantly,

while its use in the pig farming

sector has remained static. This is

not due to decreased production

of poultry and pigs, but is a result

of the replacement of fishmeal in

the feeds used by these sectors

with other ingredients and of

improvements in feed utilization

efficacy. Admittedly, the protein

requirements of poultry and

pigs are lower than that of fish

(McDonald et al., 2002), which

tend to utilize proteins to meet basic metabolic energy requirements (De Silva and

Anderson, 1995). Genetic improvements of poultry and pigs, a result of concerted

and well-planned research outcomes, have also contributed to better feed utilization,

while there have been only limited improvements of aquaculture species in this regard

(Gjedrem, 1997). The questions, therefore, arise as to whether the aquaculture sector

can achieve likewise results, and if so when, and if not, why, and what are the limiting

factors and the pivotal constraints?

In aquaculture, unlike in poultry and pig farming, the number of species cultured is

quite high (FAO, 2006b). For example, in the Asia-Pacific region 204 species belonging

to 86 families are cultured, while on a global level 336 species belonging to 245 families

are farmed. Each cultured species has unique nutrient requirements, and many species

must be provided with externally derived food, particularly those reared under

intensive culture practices, which often have to be provided with specially formulated

feeds that conform to their specific nutrient requirements.

The major increases in aquaculture production have occurred through the rearing of

omnivorous fish species and filter-feeding molluscs, while carnivorous fish production,

although significant, still only accounts for less than 20 percent of total production. For

certain cultured carnivorous species, particularly the salmonids, the fishmeal content of

the diets has been significantly reduced without loss of performance and flesh quality

or an increase in negative environmental effects. This achievement has occurred in a

progressive fashion with the increased understanding of the physiology of the animal

and its application through appropriate feed formulations (Åsgård et al., 1999; Hardy,

2000). In the case of salmonids, the renowned “protein sparing effect”, the physiological

capability to “spare” dietary protein by lipids (De Silva and Anderson, 1995), which is

a common trait in coldwater species (Beamish and Medland, 1986), has enabled a gross

reduction in the fishmeal (protein) content of the feeds and resulted in the indirect

benefit of such diets being more environmentally friendly in that much less nitrogen

and phosphorous are discharged into the environment (Hardy, 2000). However, the

FIGURE 11

Changes in the proportion of fishmeal usage by different sectors

over the years, including a projection for 2010

Source: Pike and Barlow (2002)

0%

10%

20%

30%

40%

50%

60%

70%

Aquaculture Poultry Pigs Others

Percent usage

1988 2002 2010