Fish aquaculture (3)

Question 1

Extensive aquaculture relies upon the …

Answer 1

Natural ecology of the aquatic system to support aquaculture production (Low control and intensity level)

Question 2

Extensive aquaculture supporting

Answer 2

Self supporting — recycling of nutrient, energy from the sun

Waste product are few , bacteria capable of breaking down waste products , don’t cause detention of water due to low fish biomass

Question 3

Extensive aquaculture input and water

Answer 3

• Very limited Input
• Often done in open water

Question 4

Which country can practice extensive ?

Answer 4

Often practiced in developing countries

Question 5

Egypt is advanced in fish aquaculture and using ….

Answer 5

semi intensive not extensive

Question 6

Extensive aquaculture control

Answer 6

little control of the environment except for predator exclusion

Question 7

Which is main predator for fish , and how I save fishes from them ?

Answer 7

Birds are the main predator because fishes are small and goes to water surface

We can use sound shots , Scarecrow or using net with small opens to prevent birds from eating fishes

Question 8

Extensive aquaculture feed

Answer 8

• Farmer does not provide food to the animals
• They forage for natural food or they are filter feeders (Herbivores) (clams, oysters, and mussels, Mugil spp., Tilapia)

Question 9

Can we consider that tilapia is true filter feeder

Answer 9

Tilapia is omnivores but it changes that along its life

Question 10

Stock exhausted meaning

Answer 10

When lakes likes “Edko , mariot , Brolos , qaron” has lower fish the natural system , we can fix this by stocking fishes in those lakes

Question 11

Due to the limitation of input & (particularly food), the cost of production in Extensive system is much lower than more intensive system . explain

Answer 11

Feed costs about 75-80% of total cost , and extensive system depend on natural feed which lowering the cost , (Lower in financial gain than intensive system)

Question 12

There Is no abrupt cut-off point between …

Answer 12

extensive and intensive aquaculture

Question 13

… Is used as an approximation to describe the middle ground

Answer 13

Semi-Intensive aquaculture

Question 14

Supplementation may take many forms including

Answer 14

1. Inorganic or organic fertilizers to improve natural productivity
2. prepared feeds (supplemental feeding)
3. Aeration to maintain dissolved oxygen levels (in emergency cases)

Question 15

How can I sure that I need to increase feed or add supplements ?

Answer 15

Weigh fishes every week and observe that the grow is slow and that will delay sales process

Question 16

How can I increase the growing rate ?

Answer 16

1. Give fertilizers to phytoplankton to increase its growth rate
2. Add supplements

Question 17

What will happen if phytoplankton suddenly die off ?

Answer 17

In natural , O2 source are phytoplankton , at its absence , the ventilation will be poor

Question 18

In normal cases when the fishes increase in size require ….

Answer 18

more O2 (End of cycle)

Question 19

How can I provide air by using hose ?

Answer 19

I can add water to pons by hose which have pressure to make air bubble

Question 20

Extensive
Pons size - Control - Cost

Answer 20

Large pons size
Low control
Low cost

Question 21

Semi extensive
Pons size - Control - Cost

Answer 21

Small pons size (Partitions)
High control
High cost

Question 22

Culture structure

Answer 22

what encloses. or supports the aquaculture organisms

Question 23

Pond culture

Answer 23

• Ponds are earthen enclosures that hold water
• Most common way to raise fish
• Easy design and low construction costs
• Need large areas of land

Question 24

Fish life cycle

Answer 24

Brooders at first then enter spawning and female starts to lay eggs and male eject semen (milt) which fertilize the eggs

The babies’ fish will be in yolk sac phase at first which rely on endogenous feed from the yolk after finish it , the fish will be frog then fingerling then grow up and reach market size

Question 25

Types of Ponds

Answer 25

Brood stock
Spawning
Fingerling
Grow-out to market size (nursery pond)
Storage pond

Question 26

Spawning

Answer 26

800 – 1000 m2

Question 27

Fingerling

Answer 27

1 faddan

Question 28

Grow-out to market size (nursery pond)

Answer 28

5 – 15 faddan

Most countries -including Egypt- work with maximum limit 5 faddan in Grow-out to market ponds → Low size , high control

Question 29

Storage pond

Answer 29

If the farm will rely on brackish water , so fresh water and marine water should mixed

Question 30

Storage pond is useful to …

Answer 30

collect fishes quickly

Question 31

Over – wintering pond

Answer 31

deep storage type , use to provide warm temp. especially for tilapia which does not tolerate low temperatures