Comparison Of Extensive And Intensive Aquaculture Systems

Question 1

What type of aquaculture is typically extensive?

Answer 1

Oyster farms with low inputs
Filter planktonic organisms form seawater

Question 2

What is done with breeding in some oyster farms?

Answer 2

Young oysters are bred from selected adults
Oyster ‘spat’ settle onto cleared areas of seabed and are collected, young oysters spread out until grown large enough to be harvested (predators- crabs- removed)

Question 3

What is oyster ‘spat’?

Answer 3

Planktonic larvae

Question 4

Where are most shrimp farms?

Answer 4

Tropical seas: SE Asia and Latin America

Question 5

What are the most important species of shrimp?

Answer 5

Tiger prawn
Pacific white shrimp

Question 6

How much of the worlds mangrove has been destroyed for coastal shrimp farms?

Answer 6

10%

Question 7

How many eggs will female shrimps lay in hatcheries?

Answer 7

Up to 500,000 each

Question 8

How can ovary development and egg production be increased in shrimp aquaculture?

Answer 8

Eyestalk ablation where one or both eyestalks are broken off which simulates the low light levels which stimulate breeding because they are blind

Question 9

What happens to the eggs produced by shrimp hatcheries?

Answer 9

Shrimp larvae are fed on algae and zooplankton, as they grow shrimp moved to outdoor lagoons up to 100 ha in size

Question 10

What are the conditions like for extensive shrimp aquaculture systems?

Answer 10

Shrimps fed on plankton naturally produced in the lagoons

Question 11

Are most salmon farms intensive or extensive?

Answer 11

intensive with the control of many factors to maximise productivity

Question 12

What fish are chosen for salmon aquaculture? (characteristics)

Answer 12

chosen with desirable characteristics such as fast growth rate, shape, and brightly coloured scales

Question 13

What happens to adult salmon in breeding condition? (aquaculture- gamates)

Answer 13

stripped of their roe (eggs) and milt (sperm)
These are allowed to mix and fertilisation take place

Question 14

What happens to the fertilised eggs in salmon aquaculture?

Answer 14

raised in aerated freshwater tanks
Dead or diseased eggs are removed daily
When hatched young fish moved through series of tanks as grow being fed on fish meal pellets

Question 15

What happens to the salmon in aquaculture after 12-18 months?

Answer 15

become ‘smolts’ and are ready to enter seawater tanks
continued to be fed on fish, and plant pellets until ready

Question 16

At what weight will salmon be harvested in aquaculture?

Answer 16

3-5kg

Question 17

Why does dissolved oxygen need to be controlled for salmon? (aquaculture)

Answer 17

sensitive to low dissolved oxygen (water temp not too high)

Question 18

Where are most salmon farms? (temp)

Answer 18

Norway and Scotland where it is cold

Question 19

How are salmon farms kept aerated?

Answer 19

water sprays and weirs

Question 20

Why is water flow controlled in salmon farms?

Answer 20

kept fairly high to produce more muscular fish as swim against current
direction constant (circular tanks) reducing injuries

Question 21

How are pest, disease and parasites controlled in salmon farms?

Answer 21

removing diseased fish and selective use of antibiotics and pesticides

Question 22

What might be done to predators in salmon farms?

Answer 22

may be removed

Question 23

Why are light levels controlled in salmon farms?

Answer 23

controlled to induce the smoltification of young fish as they mature

Question 24

How is efficiency of the food chain in salmon farms controlled?

Answer 24

salmon are carnivores so fed fish meal pellets with low value fish (sandeels, herring, anchovy and sardines) similar to natural food
Food chain efficiency increased by adding food from lower trophic levels (plant foods + vegetable oils)

Question 25

What is poly culture?

Answer 25

When food is produced form multiple species by rearing species together that are not competitions

Question 26

How can selective rearing of predators take place in poly culture?

Answer 26

Selective rearing of predators with other species can increase the production of larger fish by controlling the survival of smaller fish that could compete with larger fish

Question 27

How can bottom feeders be useful in poly culture?

Answer 27

Disturb the sediment and re-suspend nutrients which increase the growth of plants and phytoplankton

Question 28

What are some examples of poly-culture systems?

Answer 28

Silver carp feed mainly on phytoplankton, big head carp feed mainly on zooplankton, grass carp and tilapia feed mainly on vegetation, common carp bottom feeders(feed on molluscs, insects, re-suspend sediments), Catfish and perch eat small fish and prevent over-reproduction of species that breed well (tilapia)

Question 29

What does IMTA stand for?

Answer 29

Integrated Multi-Trophic Aquaculture

Question 30

What is IMTA? (Aquaculture)

Answer 30

Type of poly culture system where species in different trophic levels benefit from each other

Question 31

What are the different parts of IMTA? (Aquaculture)

Answer 31

Fed aquaculture
Inorganic extractive aquaculture
Organic extractive aquaculture

Question 32

What is fed aquaculture of IMTA?

Answer 32

Species that are given food (shrimp and salmon)

Question 33

What is the inorganic extractive aquaculture part of IMTA?

Answer 33

Species that absorb inorganic nutrients for growth (algae/ seaweed)

Question 34

What is the organic extractive aquaculture part of IMTA?

Answer 34

Species that catch food items such as plankton (filter feeding shellfish)

Question 35

What is aquaponics?

Answer 35

Combination of hydroponic crop production with aquaculture

Question 36

How does aquaponics work?

Answer 36

Water from aquaculture system used in hydroponic system
Drainage water from from hydroponic system

Question 37

How does the hydroponic system benefit form aquaponics?

Answer 37

Supply of inorganic nutrients and organic matter is increased

Question 38

How does the aquaculture system benefit from aquaponics?

Answer 38

Nutrients that could lead to deoxygenation are removed

Question 39

What are suitable hydroponic species? (Aquaponics)

Answer 39

Leafy salad vegetables such as lettuce, spinach, herb and watercress

Question 40

What are suitable aquaculture species? (Aquaponics)

Answer 40

Tilapia
Carp
Catfish

Question 41

What are rice-fish systems?

Answer 41

Rice is grown in flooded padi fields, fish can also be kept in the field increasing overall food production