WEEK THREE
SUBJECT: BASIC SCIENCE
CLASS: GRADE 8
TERM: SECOND
TOPIC: FISHERY AND FISH
FARMING (CONTINUATION)
PROCESSING AND
PRESERVATION OF FISH: Fish and livestock products are like some
other agricultural products which are perishable e.g. tomatoes, cassava,
fruits, etc. They get spoilt quickly if not properly handled, processed and
stored. In this respect, there have been a number of methods which have been
developed to avoid such spoilage.
Objectives of Preserving Fish
and Livestock Products:
(i) To
retain the quality of the fish for a long period of time
(ii) To
protect the products from total spoilage.
(iii) To
avoid wastage and shortage.
(iv) To
ensure their availability all the time.
(v) To
maximize farmers' profit.
Methods of Preserving Fish
and Livestock Products: When fishes are caught, they are usually
processed promptly to avoid rapid deterioration. Thus, fish should be bled
quickly by cutting the head and removing the gut. Care must be taken to avoid
breaking the gall bladder. This will make the flesh of the fish bitter to taste
when eaten. The fishes are then washed thoroughly with safe potable water and
may then be subjected to a number of preservation methods. In the village,
fishes are usually salted and sun-dried or salted and smoked over a low fire to
a crusty-brown sweet-smelling flavor. In big boats on the sea, fishes are
stored in ice or refrigerated in a big box meant for the purpose. Fresh fish
which are stored under cold temperatures become frozen and will need to be
thawed when needed for further processing. Methods of preserving fish;
Drying: It is
primarily aimed at eliminating the moisture content of the fish in order to
discourage the decomposition activities of microorganisms which cause spoilage.
This may be achieved by the application of heat from sources like sun, naked
fire (oven), etc.
Salting: This
involves the addition of a suitable quantity of salt to the fish in order to
prevent spoilage for an appreciable period of time.
Canning: It is
the method by which the processed fish is enclosed in a sterilized can in order
to prolong its quality for a longer time and for easy handling. Fish can be
stored in cans in salted water, tomato sauce or in vegetable oil. This system
of storage requires a lot of equipment for processing and is a form of
industry. The student is probably familiar with sardines and tuna fishes sold
in local markets, supermarkets and provision stores. These fishes are preserved
in small rectangular or cylindrical tin cans and can be kept for long periods,
if completely sealed. The fishes are usually cooked during preparation and come
out of the tin ready for eating. Canned fish industry is now being embraced in
some countries in West Africa. A number of North African countries like
Tunisia, Morocco and Libya, however, can their smaller sardines which they
export to the West African markets.
Refrigeration: In this
method, fishes are kept in refrigerators in order to apply a cold temperature
on microorganisms, whose activities cause spoilage. In such an environment, the
microorganisms cannot perform and thus are rendered inactive. They may not even
survive the cold and so they die. In this method fish becomes frozen and would
need to be thawed first before being processed for consumption.
Smoking: This
entails placing the fish over a smoking fire. It is a way of reducing the water
content to avoid spoilage until the fish is consumed. Smoking can continue all
day as long as the fish is not ready yet for consumption. Fish smoking is the
most important process of fish preservation in Nigeria. It can be carried out
by the use of simple ovens of mud on a charcoal or wood fire over a wire gauze.
The type of equipment that is used varies from one fishing area to another. A
common modern adaptation is the use of a section of a 200 litre drum over which
a wireguaze of about five cm to ten cm mesh is put. A slow fire of wood or
charcoal is kept under the oven. Where the oven is made out of a full-sized
drum, openings are provided at the sides through which metallic crossbars are
fitted to form a support on which additional racks can be placed. This
arrangement allows for up to three or four grill and for a larger quantity of
fish to be smoked in one operation.
In areas
where drums are not available, cylindrical shaped kilns made of mud are used
for smoke-drying fish. The inner surface of such mud kilns is hedged at four
levels to help support metal rods on which wide mesh trays are laid. A
semi-circular vent through which firewood can be introduced is placed at the
bottom as in the drum and grill type The lowest horizontal support bar should
be about 0.6 metres from the ground, with a distance of about 2 metres between
the horizontal bars. In some parts along the River Niger, fish is smoked in
special huts built on the eastern side of the fishermen's dwellings, due to the
prevailing west winds. The fish is then stored in a post-smoking storage shed.
Frying: This is
a process whereby a cleaned fish is fried in hot vegetable oil. Such can be kept for a fairly long period of
time before being consumed.
FISH FARMING: Fishing is a term used to describe the
process of harvesting fish and other aquatic animals from a body of water.
There are a number of methods and equipment available to the farmer for fish
harvesting. However, the choice of any of these methods and equipment depends
on area, type of harvesting, type of fish or other aquatic animal to be caught.
The following are the general methods and equipment of fish harvesting;
(a) Partial Harvesting: This is
a type of harvesting in which only a desired proportion of the fish population
is cropped (harvested) at a given period of time. The fishing materials that
are used in this respect are hook and line, net and hook, boat and hook, bow
and arrow, spear, etc.
(b) Total Harvesting: In this
type of harvesting, all the fish and other aquatic animals in the pond, stream,
or river are harvested at once. This is usually done through the draining of
water and packing of fish and every other desirable aquatic animal.
MAINTENANCE OF FISHING
TOOLS AND EQUIPMENT: Fishing tools are maintained so that they
will be useful for a very long period of time.
ASSIGNMENT
OBJECTIVE QUESTIONS:
1.
A method that can serve both as processing and preservation of fishes in large
quantities is A. canning B. freezing C. frying D. salting E. sun drying
2.
Which of the following is NOT a necessary condition for siting a fish pond? A.
Access to improved varieties B. Adequate and constant water supply C.
Availability of feed supplement D. sloppy and clayey locations E. Swampy and
woody locations
3.
The method of harvesting in which spears are used to catch big fishes
is known as A. electro fishing B. ultrasonic C. netting D. impaling E.
trapping
4.
The introduction of fingerlings into the pond is called A. clearing B.
fertilization C. inoculation D. liming E. stocking
5.
Fingerlings refer to the young of A. duck B. fish C. guinea pig D. rabbit E.
turkey
6.
The following are methods of preserving fish except A. canning B. cooking C.
refrigerating D. salting E. drying
THEORY:
1.
State two objectives of preserving fish.
2.
List six methods of preserving fish and explain two.
3.
What is fishing?
4.
Differentiate between partial harvesting and total harvesting.
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