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FISHERY – THEORY – ANSWERS
4 ai)
Water quality refers to the chemical , physical , biological , and radiological characteristics of water. It is a measure
of the condition of water relative to the requirements of
one or more biotic species and or to any human need or
purpose .
4 aii )
i ) temperature ,
ii) dissolved oxygen
iii ) pH level
iv ) Ammonia .
v ) Water turbidity
4 aiii)
i ) Temperature is thermometer
ii) Dissolved oxygen is dissolved oxygen sensor
iii ) PH level is PH meter,
iv ) Ammonia is litmus paper
v ) Water turbidity is nephelometer or turbidimeter
4 bi)
– Advantages –
i ) It yield high harvest
ii) It increases farmers income
– Disadvantages-
i ) High capital is required
ii) High technical know how is required
4 c )
diagrams
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5 ai)
stocking- is the practice of raising fish in a hatchery and releasing them into a river , lake , or the ocean to supplement existing populations , or to create a population where none exists .
Stocking – density is the quantity of fry or fingerlings per unit of water area .
5 aii )
i ) Fertilization of the pond / addition of manure.
ii) Maintaining water level .
iii ) Repair of pond and the fence .
iv ) Cropping / selective removal of excess fish .
5 bi)
i ) Pseudomonas fluorescens
ii) Ichthyophthirius multifiliis
iii ) fungal infections
iv ) Eustrongylides
v ) copepods
5 bii )
i ) Anorexia ( loss of appetite, refusing all food , with consequential wasting)
ii) Rapid breathing
iii ) Hiding abnormally
iv ) Resting on the bottom
5 c )
Area = length x breadth
Area = 30 x 20
Area = 600 m ²
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2 ai)
i ) Chilling and Storage equipment
ii) Freezing and Refrigerating equipment
iii ) Fish Silage equipment
iv ) Smoking equipment
2 aii )
i ) Freezing and Refrigerated Storage
Even when the most effective chilling methods and further
chilled storage of raw fish and fish products are applied , shelf
life is limited . Freezing is needed to extend shelf life for long
periods . This can be achieved by changing two parameters :
first , a considerable decrease in temperature , and second , by
freezing the water in the fish tissue
ii) Fish silage equipment : During fish processing , a large quantity of offal is produced and its proper utilization poses a problem , particularly for
smaller processing plants . Fishmeal production is not
profitable because of a low supply of the raw material , and
thus production of a liquid form of this fish product is the only
simple solution.
2 bi)
culture – fishery is the cultivation of selected fishes in confined areas with utmost care to get maximum yield . The seed is stocked , nursed and reared in confined
waters , then the crop is harvested. Culture takes place in ponds , which are fertilized and supplementary feeds are
provided to fish to get maximum yield .
Capture- fishery refers to all kinds of harvesting of
naturally occurring living resources in both marine and freshwater environments . Source : GreenFacts. More : On
a broad level , capture fisheries can be classified as
industrial , small – scale / artisanal and recreational .
2 bii )
i ) It feeds on small fish in the pond
ii) It serve as disease vectors
iii ) It competes with the fish in the pond for available resources
iv ) It contaminate the fish pond
2 c )
– Similarities-
i ) Presence of eyes
ii) Presence of operculum / gill cover
– Differences –
i ) Catfish have small eyes and a mouth which is suited to sucking . Tilapia, has a deep body with a long dorsal fin and proportional features .
ii) Catfish belong to the order Siluriformes and to the superorder
Ostariophysi , Tilapia, on the other hand , belongs to the Cichlidae family of the Perciformes ( meaning Perch – like )
order .
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