Fish as feed inputs for aquaculture – Practices, sustainability and implications: a global synthesis 33
5.1 Environmental impacts of aquafeed use
For the purposes of this paper, the environmental impacts of fish-fed aquaculture
operations can be viewed as follows (Tacon, 2009; Huntington, 2009).
5.1.1 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 upon marine capture fisheries for
sourcing finfish and crustaceans for reduction to fishmeal and fish oil (Goldburg,
Elliot and Naylor, 2001); - increased pressure upon marine capture fisheries for sourcing forage fish species for
reduction to fishmeal and fish oil for use by the aquaculture sector (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 and
eventually to the consumer (Hites et al., 2004a, 2004b; Foran et al., 2005).
Indirect environmental impacts include:- removal of large quantities of forage fish species from marine ecosystems and
potential ecosystem and biodiversity impacts upon other dependent piscivorous
animal species, including other fish species, birds and mammals (Huntington et
al., 2004; Worm et al., 2006; Skewgar et al., 2007); and - exportation and loss of valuable fishmeal and fish oil resources from one continent
and ecosystem (the Americas) to another (Europe, Asia) ( Naylor et al., 2000).
5.1.2 Trash and baitfish
In Asia, trash fish is an important dietary component (either fed directly or as part
of a farm-made feed), particularly for the extensive culture of shrimp, Pangasius
catfish, Macrobrachium, crabs and snakehead. A recent survey in Viet Nam indicated
that farmers perceived trash fish to have a considerable impact on the environment,
especially when incorporated into farm-made feeds, possibly due to mixing with
chemicals and to prophylactic disease treatments (Sinh, 2006, 2007).
Direct environmental impacts include:- increased environmental pollution resulting from the use of highly perishable and
water-polluting trash fish-based feed items (Tacon et al., 1991; Ottolenghi et al.,
2004); - increased biosecurity and disease risks due to the feeding of unpasteurized
trash-fish products to cultured fish and their use as bait for wild fish (Gill, 2000;
SCAHAW, 2003; Hardy, 2004; anon, 2005); - increased fishing pressure on wild juvenile target species used for fattening, and
the capture of pelagics for feeding and bait use (Dalton, 2004); - increased risk of over-fishing of available fish stocks due to the use of the captured
juveniles of higher-value commercial food-fish species (FAO, 2004b); and - increased fishing pressure on species that were not previously fished commercially,
such as the round sardinella in the western Mediterranean Sea, where the use of
trash fish is limited to tuna fattening, with possible consequences for one of
tunas’ main predators, the common dolphin, as noted by the World Wide Fund
for Nature (WWF). In addition, use of trash-fish raises the possibility of