Wild fish and other aquatic organisms as feed in aquaculture in the Americas 191
- ENVIRONMENTAL IMPACTS OF FISH-FED AQUACULTURE
Aquaculture feeds and feeding regimes play a major role in determining the
environmental impact of semi-intensive and intensive finfish and crustacean farming
operations (Tacon and Forster, 2003; Mente et al., 2006). This is particularly true for
those intensive farming operations employing open aquaculture production systems,
which include net cages/pen enclosures placed in rivers, estuaries or open waterbodies;
and land-based flow-through tank, raceway or pond production systems (Black, 2001;
Goldburg, Elliot and Naylor, 2001; Brooks, Mahnken and Nash, 2002; Lin and Yi,
2003; Piedrahita, 2003; Muñoz, 2006). This is perhaps not surprising, because the bulk
of the dissolved and/or suspended inorganic and/or organic matter contained within
the effluents of intensively managed open aquaculture production systems is derived
from feed inputs, either directly in the form of the end-products of feed digestion
and metabolism or from uneaten/wasted feed (Cho and Bureau, 2001), or indirectly
through eutrophication and increased natural productivity (Tacon, Phillips and Barg,
1995).
It follows from the above that the rate of supply and assimilation of fish-fed
aquaculture operations (includes the use of fishmeal, fish oil and/or trash fish-based
feeds) will play a major role in dictating the nutrient and/or waste outputs from the
aquaculture production facility. Moreover, it also follows that these outputs and their
environmental impacts will, in turn, vary depending upon the farming system employed
(open or closed farming systems), on-farm feed/nutrient and water management, and
the assimilative capacity of the surrounding aquatic and terrestrial environment.
In general, the higher the intensity and scale of production, the greater the nutrient
inputs required and consequent risk of potential negative environmental impacts
through water use and effluent discharge (Figure 47).
For the purposes of this paper, the environmental impacts of fish-fed aquaculture
operations can be viewed as follows:
5.1 Fishmeal and fish oil
Direct environmental impacts include:
- increased environmental pollution resulting from the rapid growth and expansion
of semi-intensive shrimp farming and intensive salmonid farming operations
dependent upon the use of compound feeds containing fishmeal and fish oil as
major dietary nutrient sources (Tacon, 2002, 2005);
- increased dependence of the aquaculture sector within the Americas upon marine
capture fisheries for sourcing finfish and crustaceans for reduction into fishmeal
and fish oil (Goldburg, Elliot and
Naylor, 2001; Kristofersson and
Anderson, 2006; Skewgar et al.,
2007); and
- use of environmentally
contaminated fishmeals and fish
oils in aquafeeds, and consequent
potential risk of transferring
contaminants to the cultured
species, the environment and the
end consumer (Hites et al., 2004a,
2004b; Foran et al., 2005).
Indirect environmental impacts
include:
- removal of large quantities of
forage fish species from the
FIGURE 48
Chilean exports of pelagic fish species for direct human
consumption (tonnes and thousand US$)
Source: Jara (2006)
