4 Fish as feed inputs for aquaculture – Practices, sustainability and implications
This compilation provides a comparative analysis of the different regional patterns
in terms of the status of and trends in the use of fish as aquafeeds (the species and
volumes involved, as well as the seasonal and spatial distribution of use), the actual
types of uses in aquaculture (either directly as trash fish or in compounded diets), the
relative amount being used by aquaculture and the potential alternative uses (e.g. for
direct human consumption).1.3 Scope
In this study, the wild fish destined for inclusion in aquafeeds will include the so-called
“feed-fish” stocks (also known as reduction fisheries) that are directly targeted for
fishmeal production, together with bycatch species and those species (including offal
and trimmings) reduced to fishmeal in certain market situations. It also includes the
so-called trash or low-value bycatch that is currently the mainstay of Asian small-scale
aquaculture. The review is not restricted to finfish feed sources – other marine species
used in aquafeeds such as squid, krill and shrimp are also included.- OVERVIEW OF AQUACULTURE SYSTEMS AND PRACTICES
This section looks at the contrasting nature of aquaculture undertaken in different
regions of the world, examines the past trends in production and then attempts to
forecast where the industry will be in the next decade.
2.1 Current status and trends
Aquaculture is the farming of aquatic organisms in inland and coastal areas, involving
intervention in the rearing process to enhance production and the individual or
corporate ownership of the stock being cultivated (FAO, 2009)^1. For the purpose of
this report, four broad categories of aquaculture are considered, based upon the relative
position of the animals cultured in the trophic hierarchy and thus the fishmeal and fish
oil in their diets (Tacon, Hasan and Subasinghe, 2006).- Carnivorous finfish: those species dependent upon high protein levels in their diet,
normally derived from animal sources. This group includes the salmonids, as well
as many marine and freshwater species such as seabass, seabream, eels, amberjack,
groupers and snakeheads. These species require from 20 to 40 percent fishmeal in
their diets. - Herbivorous/omnivorous finfish: those species that have lower protein requirements
(i.e. <20 percent) that can be derived from both plant and animal sources. This
group includes grass carp, common carp, other cyprinids, tilapias, milkfish and
catfish, all of which require around 5 percent fishmeal content in their feeds. - Omnivorous/scavenging crustaceans: those species include the marine shrimps,
freshwater prawns, crabs and crayfish that currently require between 15 and 25
percent fishmeal in their diets. - Filter-feeding finfish: those species that are able to derive their dietary requirements
from phyto- and zooplankton and thus do not necessarily need supplementary
feed. They include silver carp, bighead carp, catla and rohu.
2.1.1 Carnivorous finfish
Although relatively new to aquaculture when compared with the cyprinids, which
have been cultivated for thousands of years, a combination of the development of
high performance compounded feeds and technological advances in marine fish
hatchery production has resulted in a huge expansion in the largely intensive culture of
carnivorous species over the last 50 years. This includes the production of channel catfish(^1) FAO Glossary of aquaculture (accessed on 31 July 2009) (http://www.fao.org/fi/glossary/aquaculture/
default.asp)