248 Fish as feed inputs for aquaculture – Practices, sustainability and implications
This purchasing strategy could be updated regularly to reflect changes in
different fishing practices and the latest “sustainability assessments”, together
with emerging trends in fish nutrition and alternative feed materials. The use
by procurement departments of environmental management systems such as
International Organization for Standardization (ISO) ISO 14 001 to ensure that
procurement strategies minimize the environmental implications of purchasing
should also be considered.- Use of non-fish protein and oil: Greater knowledge should be developed about
the options for substituting different fish species with non-fish protein and oil at
different times of year to obtain a required fishmeal quality and specification. - Premium branding: European aquaculture, in partnership with its own customers,
should seek to develop its premium brand image by encouraging its feed suppliers
to move toward targets for achieving sustainable supplies.
- ENVIRONMENTAL IMPACT OF AQUACULTURE BASED ON FEEDFISH AS
INPUTS
While the sourcing of sustainable raw materials for aquafeeds is only just now becoming
a serious issue in European aquaculture, the impact of aquafeeds on the environment
has been on the agenda for a number of years after the potential magnitude of
waterbody eutrophication and other effects of intensive aquaculture were realized.
As a result, the content, digestibility and physical structure of pelleted feeds have
undergone considerable evolution to minimize wastage and their subsequent effect on
the environment.
5.1 Environmental impacts of aquafeed use in Europe
Compounded fish feeds, especially for carnivorous fish such as salmon, trout, seabass
and seabream, are now used for over 99 percent of European aquaculture production
of finfish. Food-derived waste has four sources (Dosdat, 2003):- Uneaten feed. This is the case with artificial feeding, generally due to poor
husbandry, fish diseases or unsuitable environmental conditions. - Undigested feed. This is the case mainly in bivalves when the control of intake and
repletion is insufficient. Thus, they ingest more than they can process and release
the intact microalgae in the form of faeces called pseudo-faeces. - Indigestible compounds. Complex molecules present in the feed are split into small
molecules that either can or cannot cross the intestinal barrier during digestion.
Those that cannot, due to their size or their shape, are rejected in the form of
particulate matter (faeces). - Excreta. Excretion is the physiological phenomenon by which molecules that
come into the body and dissolve in the plasma are released after being processed
and degraded. These are soluble compounds that are discharged into the water
through particular organs, such as the gills and the kidney. Thus, aquatic animals
are directly subjected to the effect of their own waste products.
The impacts of these waste materials can be divided into two main areas of
concern: - Hyper-nutrification of the waterbody: Eutrophication is the process of natural or
anthropogenic enrichment of aquatic systems with inorganic nutrient elements.
The long-term eutrophication of coastal and estuarine waters results from the
additions of both dissolved inorganic and organic nutrients and increased biological
oxygen demand (BOD). Dissolved inorganic nutrients released by finfish culture
and regenerated from sediments enriched with sedimented organic matter may
stimulate phytoplankton production and increase oxygen demand. The degree of
nutrient enrichment is influenced by the scale of aquaculture, local hydrographic