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Fish is a very perishable food commodity that
requires proper handling and preservation to
increase its shelf life and retain its quality and
nutritional attributes.
The first obvious way to avoid spoilage and loss
of quality is to keep caught fish alive until
cooking and consumption. Handling of live carp for
trade and use has been practised in China for more
than three thousand years. Today, keeping fish
alive for eventual consumption is a common
fish-handling practice worldwide. To do so, fish
are first conditioned in a container with clean
water, while the damaged, sick and dead fish are
removed. Fish are starved and, if possible, water
temperature is lowered in order to reduce metabolic
rates and make fish less active. Low metabolic
rates decrease the fouling of water with ammonia,
nitrite and carbon dioxide that are toxic to fish
and impair their ability to extract oxygen from
water.
A large number of fish species are usually kept
alive in holding basins, floating cages, wells and
fish yards. Holding basins, normally associated
with fish culture companies, can be equipped with
oxygen control, water filtering and circulation and
temperature control. Simpler methods are also used.
For instance, large palm woven baskets act as
floating cages in rivers (China) or simple fish
yards are constructed in a river's backwater (South
America). Also, the transportation of live fish
ranges from very sophisticated systems installed on
trucks that regulate temperature, filter and
recycle water and add oxygen, to very simple
artisanal systems of transporting fish in plastic
bags with an atmosphere supersaturated with
oxygen.
For dead fish, handling operations after capture
are: transferring catch from gear to vessel,
holding of catch before handling, sorting/grading,
bleeding/gutting/washing, chilling, chilled
storage, unloading. These operations can be
performed in several ways, from manual methods to
fully automated operations. The number of
operations and the order in which they are
performed depend on the fish species, the gear
used, vessel size, duration of the voyage and the
market to be supplied. It is crucial to provide a
continuous flow in handling and to avoid any
accumulation of unchilled fish, thereby bringing
the important time-temperature phase under complete
control. It is also essential to improve working
conditions onboard fishing vessels by eliminating
those catch-handling procedures that cause physical
strain and fatigue to fishers. Nowadays, this is
possible in industrial fisheries because of
equipment and handling procedures designed to
eliminate heavy lifting, unsuitable working
positions and rough handling of fish.
Ice is the oldest method of preserving fish
freshness. Currently, it is widely used thanks to
mechanical refrigeration, which makes ice readily
and cheaply available. In addition, ice keeps fish
moist, has a large cooling capacity, is safe, is a
portable cooling method that can be easily stored,
transported and used by distributing it uniformly
around fish. Ice can be produced in different
shapes - the most commonly used to cool fish are
flake, plate, tube and block. Block ice is crushed
to chill fish.
For artisanal fisheries, FAO developed
appropriate handling technologies to preserve fish
freshness. The use of ice on small boats, pirogues,
canoes, etc. has only been possible through the
introduction of insulated containers - especially
in tropical, warm climates. These containers are
designed and constructed locally, using natural or
artificial insulating materials, with enough
handling flexibility. Two very interesting cases
are the introduction of insulated fish containers
in the pirogue fleet of Senegal and onboard "navas"
-- the traditional fishing vessels of Kakinada in
Andhra Pradesh, India. The Senegalese example is
now spreading steadily to comparable fisheries in
West Africa (Gambia, Guinea-Bissau and Guinea) that
are adopting the use of similar insulated
containers.
After landing, fish handling procedures are
similar to those described above. They often
include sorting/grading, gutting/washing, chilling,
chilled storage, unloading. These operations can
also be done manually or using fully-automated
operations.
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