1. Aquaculture

2. Is aquaculture the answer?
Aquaculture (fish farming) is the fastest growing sector of the world food economy
Fish may replace beef as the major source of protein
Fish are more efficient protein producers than cattle & therefore may replace beef as the major source of protein

3. Is aquaculture the answer?
It takes 7 kilograms of grain to add 1 kilogram of live weight to a cow
It takes 2 kilograms of grain to add 1 kilogram of live weight to a fish

4. Aquaculture Locations
Most meat production takes place in industrial countries but 65% of fish farming is in developing countries
Aquaculture is extremely important in China, Bangladesh, Indonesia, and Thailand
Among industrial countries, Japan (scallops, oysters), the United States (catfish) and Norway (salmon) are the leaders

5. China Carp are reared in ponds, lakes, reservoirs and rice paddies
Involves polyculture - 4 types of carp are reared together = > efficiency than monoculture
They feed at different levels of the food chain:
Silver carp feed on phytoplankton
Bighead carp feed on zooplankton
Grass carp feed on vegetation
Common carp feed on detritus that settles to the bottom
Aquaculture is integrated with agriculture. Farmers use agricultural wastes such as pig manure to fertilize ponds, thus stimulating the growth of plankton
As land and water become scarce, China’s fish farmers are intensifying production by feeding more grain concentrates to raise pond productivity

6. Aquaculture as a Controlled Environment
What makes a good species for aquaculture?
Rapid growth rate e.g. grass carp and many mussels/oysters are very fast growing
Easily controlled life cycle e.g. oysters, Tilapia
Tolerance of fluctuating environmental conditions
Low on food chain - the lower an organism is the cheaper it is to feed so herbivores and omnivores are ideal
Efficient food conversion
Low susceptibility to disease so less money needed for antibiotics
Tolerance to overcrowding e.g. Tilapia
Availability of brood stock
Rapid breeding rate e.g. Tilapia
Oysters
Tilapia

7. Aquaculture as a Controlled Environment
Monosex culture is common
Advantages?
Higher growth rate in one sex (tilapia, salmon)
Prevention of energy diversion (gonad production)
Reduces aggression (courtship behaviour)
Greater uniformity of size
Salmon
Tilapia

8. Aquaculture as a Controlled Environment
Genetic modification of the breeding stock is becoming more common – optimises success of subsequent breeding programme
Characteristics such as growth rate can be rapidly improved by traditional selection techniques 6 15
0.100
Tilapia 1
14.2
5.700
Atlantic Cod 4 13
4.000
Trout
10.1
0.250
Coho
Number of generations
Gain per generation
Mean weight (kg)
Species used

9. Breeding Many species do not spawn in captivity
Ovulation is induced thus hatching time can be optimised
Spawning can be carefully controlled via hormones, pheromones, maintenance of optimal temperature & photoperiod and by providing appropriate vegetation/food and nesting material
Hormonal injection likely to cause less environmental problems that continual release into the water

10. Salmon Spawning Grade and separate by sex Check for ripeness
Treat/prime for injections
Remove all dead
eggs etc.
Anaesthetize, strip for eggs/milt
Check milt for viability
Incubator
Add eggs to milt and mix
Egg washing
Water harden (min-1 hr)
Micropyle closure

11. Breeding Conditions
The abiotic environment is controlled to maximise growth:
Factor
Why control?
Oxygen levels
Optimise for aerobic respiration
Temperature
Fish don’t lose heat unnecessarily pH
Affects solubility of ions
Ammonia levels
Possibly toxic/ influence pH
Light levels
Influences spawning
Antibiotics, herbicides & fungicides are used to control infection and pests
Rearing in enclosed tanks, ponds or cages prevents predators entering and eliminates competition for food
The quantity and nutrient composition of food is carefully controlled to optimise growth and minimise waste

12. Complete the table Measure Why? High stocking densities
More product per unit area
Reduce energy loss via respiration so more of their energy goes into growth
Fish movement is restricted
Fed concentrated pellets of carefully formulated food
Maximise growth
Antibiotics/pesticides
Reduce disease
Maintain oxygen levels but ensure that fish are not using lots of energy swimming against a current
Water current speed controlled

13. Excess Nutrients Excess nutrients falling towards seabed result in:
Eutrophication
Increased primary (phytoplankton) production
Changes in phytoplankton populations
Deoxygenation of water column
Increase in algal blooms, some toxic
Decreased primary production near shellfish beds
Increased chemical oxygen demand
Increased microbial activity
Increased biological oxygen demand
Changes in macrofaunal populations
Production of H2S and methane
40+ meters from cages
Algal blooms

14. Food Wastage Food wastage can be minimized by:
Feed timing synchronized to natural rhythmicity
Optimize feed pellet size
Optimal feed shape, color, contrast, texture, taste
Distribution of feed should be maximized to ensure total use
Sustained exercise

15. What are the environmental impacts of aquaculture
What are the environmental impacts of aquaculture? Write down at least 5 that you can think of
Overfishing of food species
Predator control
Parasites
Gene pool contamination
Introduced species
Habitat loss
Pesticides
Antibiotics
Organic waste
inorganic waste
Add to each heading from the teachers notes and from the textbook.
Set out your work in either a table or spider diagram

16. Quiz
Explain the impacts shown in each graph

17. Quiz Explain the impacts shown in each graph
Uneaten food and faeces resulted in a population explosion of bacteria that created a high BOD = lowering dissolved oxygen (DO) levels
Increase in electrical conductivity =increase in levels of inorganic nutrients (ions)
Turbidity = uneaten food/faeces

18. Example 1 - Salmon
Grown mostly in industrial countries, principally in Norway, for consumption in those countries
Salmon are carnivores, fed fishmeal made from anchovies, herring or fish processing wastes
So to get one ton of salmon it may take up to 5 ton of wild fish
Farmed salmon are bred for fast growth and not for survival in the wild. So if they escape when cages are damaged by storms or predators such as seals, they can breed with wild salmon, weakening the latter’s capacity to survive
High concentrations of faeces and uneaten food can cause organic pollution – reducing BOD – or cause eutrophication
Anaerobic or toxic sediments can kill benthic communities
Lice infestations have to be controlled by pesticides –which can contaminate the ocean

19. Example 2 - Shrimp
Grown largely in developing countries - Thailand, Ecuador and Indonesia - for export to developed countries
Shrimp are often produced by clearing coastal mangrove forests
Mangroves protect coastlines and serve as nurseries for local fish
Mangrove destruction destroys habitat
leads to erosion
causes a decline of local fisheries that will actually exceed the gains from shrimp production, leading to a net protein loss
Shrimps are also fed fishmeal, so increasing pressure on ocean fish stocks

20. Lessons Learned Use herbivorous fish Use polyculture
Rear fish in combination with rice
Use only fishmeal made from bycatch
Use mangrove buffer zones
Replant damaged mangroves
Polyculture: oyster, kelp and abalone
Mangrove
Rice field and fish lake

21. Further Research
Marine Conservation Society UK pressure group working to protect marine environment and its wildlife publish the Good Fish Guide
Marine Stewardship Council International charity to ensure fisheries are managed sustainably
RSPB Fisheries good sections on the effect of fisheries policies on seabird populations