Extent To Which Aquaculture Can Replace Fishing

Question 1

What has happened to global fish catches over time?

Answer 1

Increased until 1990 where it has plateaued

Question 2

What has happened to aquaculture as fish catch has plateaued?

Answer 2

As demand for seafood has grown aquaculture production has expanded and may equal wild catch

Question 3

What is a more productive way of aquaculture compared to carnivorous fish?

Answer 3

Raising herbivorous fish (Tilapia) is very productive as amount of food produced per unit area is high

Question 4

Why are carnivorous fish chosen over herbivores in most cases?

Answer 4

Although less energy efficient, often more popular with consumer (salmon)

Question 5

Why do fish have very low basal metabolic rates?

Answer 5

do not use energy to keep warm or for support

Question 6

What does having a low basal metabolic rate mean for fish food conversion ratio?

Answer 6

have much higher FCR then mammal or bird livestock

Question 7

What is the food conversion ratio?

Answer 7

quantity of food required to produce a unit of growth (usually 1kg)

Question 8

What are the food requirements of herbivorous fish?

Answer 8

may eat plants and algae that grow naturally in the water

Question 9

How can food be increased for herbivorous fish in aquaculture?

Answer 9

Adding plant nutrients
Supplementary feeding (adding plant material as crop waste)

Question 10

What are the food requirements of carnivorous fish? (aquaculture)

Answer 10

Usually fed on fish that have a lower economic value (Salmon eat sandeel fish meal)

Question 11

What is the problem with using sandeel in fish meal for salmon aquaculture?

Answer 11

Overfishing of sandeels causing population decline in other species that eat sandeels (puffins and terns)

Question 12

What has been done to to reduce over fishing of sandeels?

Answer 12

plant based foods but the meat produced may be less tasty

Question 13

What is an example of stock collection?

Answer 13

Species such as blue fin tuna do not breed well in captivity so young fish are caught in sea and raised in larges cages at sea
Tuna aquaculture cant continue without wild population

Question 14

What are the environmental impacts of aquaculture?

Answer 14

Food supply impacts
Habitat loss
Pesticide pollution
Development of antibiotic resistant bacteria
Control of wild predators
Impacts of controlling lice
Wild gene pool impacts
Introduction of non-indigenous species
Organic waste pollution

Question 15

What is the environmental impact of aquaculture on food supply?

Answer 15

overfishing of wild fish to make food pellets
reducing population of fish and species that eat them (seabirds)
Final products (fish) increase food availability

Question 16

What is the environmental impact of aquaculture on habitat loss?

Answer 16

Habitat destruction during construction especially lagoons in mangroves

Question 17

What is the environmental impact of aquaculture on pesticide pollution?

Answer 17

pesticides used to control weed and crustacean growth may kill wildlife

Question 18

What is the environmental impact of aquaculture on development of antibiotic resistant bacteria?

Answer 18

Anti-biotics used to prevent or treat diseases may lead to the development of antibiotic resistant bacteria
Resistance may transfer to humans

Question 19

What is the environmental impact of aquaculture on wild predators?

Answer 19

culling predators such as seals and fish eating birds reduces the predator population so fewer fish are eaten

Question 20

What is the environmental impact of aquaculture on controlling lice?

Answer 20

Parasitic lice reduce fish growth and increase risk of virus and fungus infections (can spread to nearby wild population)
Controlled with chemicals such as:
-Hydrogen peroxide wash
-Azamethiphos (organophosphate pesticide)
-Pyrethroid pesticides
May kill local wildlife

Question 21

What is the environmental impact of aquaculture on the wild gene pool?

Answer 21

fish that escape may breed with wild fish and introduce disadvantageous characteristics to wild gene pool (bright colour-easily spotted)

Question 22

What is the environmental impact of aquaculture by introduction of non-indigenous species?

Answer 22

escaped non-indigenous species may colonise and become predators or competitors

Question 23

What is the environmental impact of aquaculture organic waste pollution?

Answer 23

organic waste from faeces or surplus food causes deoxygenation as it decomposes

Question 24

How can the environmental impacts of food supply in aquaculture be reduced?

Answer 24

Use of more plant products in food pellets or cultivation of herbivorous fish (Tilapia)

Question 25

How can the environmental impacts of habitat destruction in aquaculture be reduced?

Answer 25

Careful site selection (difficult for large scale developments)

Question 26

How can the environmental impacts of pesticide pollution in aquaculture be reduced?

Answer 26

mechanical cleaning of cages and biological control with crustaceans reduces need for pesticides

Question 27

How can the environmental impacts of antibiotic resistant bacteria in aquaculture be reduced?

Answer 27

lower stocking densities lowering the risk of disease so antibiotic use can be reduced

Question 28

How can the environmental impacts of wild predators in aquaculture be reduced?

Answer 28

better cage design to exclude predators

Question 29

How can the environmental impacts of controlling lice in aquaculture be reduced?

Answer 29

Tanks should hold fish of single age group so lice not transferred from old to young unaffected fish
Biological control with wrasse (can reduce wild wrasse population is caught for farms)
Washing fish in warm water

Question 30

How can the environmental impacts on the wild gene pool from aquaculture be reduced?

Answer 30

better cage designs to reduce escapes
Eggs exposed to high pressure to produce triploid fish which are sterile (grow faster)

Question 31

How can the environmental impacts of non-indigenous species from aquaculture be reduced? (not triploid)

Answer 31

cultivation of species that cannot breed in the wild (Japanese oysters in UK -too cold to breed)

Question 32

How can the environmental impacts of organic waste pollution in aquaculture be reduced?

Answer 32

Feeding is monitored to prevent over feeding
Cages located where current will disperse wastes
Freshwater aquaculture may have effluent treatment works (like sewage works)
Bacteria in reed beds can also be planted to absorb nutrients and break down organic wastes