Aquaculture

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Aquaculture
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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

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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

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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

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China

• Carp are reared in ponds, lakes, reservoirs and
  rice paddies
• Involves polyculture - 4 types of carp are reared
  together gt efficiency than monoculture
• They feed at different levels of the food chain

• 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, Chinas fish
  farmers are intensifying production by feeding
  more grain concentrates to raise pond productivity

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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

Tilapia
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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

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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

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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

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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
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Breeding Conditions

• The abiotic environment is controlled to maximise
  growth

Factor Why control?
Oxygen levels Optimise for aerobic respiration
Temperature Fish dont 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

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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
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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

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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

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What are the environmental impacts of
aquaculture?Write down at least 5 that you can
think of

1. Overfishing of food species
2. Predator control
3. Parasites
4. Gene pool contamination
5. Introduced species
6. Habitat loss
7. Pesticides
8. Antibiotics
9. Organic waste
10. 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
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Quiz
Explain the impacts shown in each graph
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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

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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 latters 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

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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

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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

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Further Research

• Marine Conservation Society www.mcs.uk.org UK
  pressure group working to protect marine
  environment and its wildlife publish the Good
  Fish Guide
• Marine Stewardship Council www.msc.org
  International charity to ensure fisheries are
  managed sustainably
• RSPB Fisheries www.rspb.org.uk good sections on
  the effect of fisheries policies on seabird
  populations