Fish aquaculture (3) Flashcards
Extensive aquaculture relies upon the …
Natural ecology of the aquatic system to support aquaculture production (Low control and intensity level)
Extensive aquaculture supporting
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
Extensive aquaculture input and water
- Very limited Input
- Often done in open water
Which country can practice extensive ?
Often practiced in developing countries
Egypt is advanced in fish aquaculture and using ….
semi intensive not extensive
Extensive aquaculture control
little control of the environment except for predator exclusion
Which is main predator for fish , and how I save fishes from them ?
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
Extensive aquaculture feed
- 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)
Can we consider that tilapia is true filter feeder
Tilapia is omnivores but it changes that along its life
Stock exhausted meaning
When lakes likes “Edko , mariot , Brolos , qaron” has lower fish the natural system , we can fix this by stocking fishes in those lakes
Due to the limitation of input & (particularly food), the cost of production in Extensive system is much lower than more intensive system . explain
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)
There Is no abrupt cut-off point between …
extensive and intensive aquaculture
… Is used as an approximation to describe the middle ground
Semi-Intensive aquaculture
Supplementation may take many forms including
- Inorganic or organic fertilizers to improve natural productivity
- prepared feeds (supplemental feeding)
- Aeration to maintain dissolved oxygen levels (in emergency cases)
How can I sure that I need to increase feed or add supplements ?
Weigh fishes every week and observe that the grow is slow and that will delay sales process
How can I increase the growing rate ?
- Give fertilizers to phytoplankton to increase its growth rate
- Add supplements
What will happen if phytoplankton suddenly die off ?
In natural , O2 source are phytoplankton , at its absence , the ventilation will be poor
In normal cases when the fishes increase in size require ….
more O2 (End of cycle)
How can I provide air by using hose ?
I can add water to pons by hose which have pressure to make air bubble
Extensive
Pons size - Control - Cost
Large pons size
Low control
Low cost
Semi extensive
Pons size - Control - Cost
Small pons size (Partitions)
High control
High cost
Culture structure
what encloses. or supports the aquaculture organisms
Pond culture
- Ponds are earthen enclosures that hold water
- Most common way to raise fish
- Easy design and low construction costs
- Need large areas of land
Fish life cycle
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
Types of Ponds
Brood stock
Spawning
Fingerling
Grow-out to market size (nursery pond)
Storage pond
Spawning
800 – 1000 m2
Fingerling
1 faddan
Grow-out to market size (nursery pond)
5 – 15 faddan
Most countries -including Egypt- work with maximum limit 5 faddan in Grow-out to market ponds → Low size , high control
Storage pond
If the farm will rely on brackish water , so fresh water and marine water should mixed
Storage pond is useful to …
collect fishes quickly
Over – wintering pond
deep storage type , use to provide warm temp. especially for tilapia which does not tolerate low temperatures
