FISH FARMING

Question 1

Name 6 methods used to increase yield?

Answer 1

Ensuring good water quality
Controlling predation
Controlling disease
Clearing waste
Managing feeding
Selective breeding

Question 2

What are the 2 types of predation in groups of fish?

Answer 2

Interspecific - between 2 unique species of fish
Intraspecific - between individual organisms in the same species of fish

Question 3

What is the process of eutrophication?

Answer 3

Artifical fertilisers contain high amounts of nitrates and phosphates, and both of these can be washed out of the soil by rain (leaching), and runs off into nearby rivers.
1. These excess mineral ions stimulate plant growth in the lake, specifically with algae
2. These algae grow and form a scum on the water’s surface
3. These algae die and are decomposed by aerobic bacteria in the water, that use up all the oxygen in the water
4. The algae still cover the river surface, blocking out water, decreasing the amount of photosynthesis-produced oxygen
5. This makes the water anoxic (very little oxygen), and only anaerobic bacteria survive,
while fish and other aerobic organisms die.

Question 4

What do farmers do to farm fish in the sea? (Example - Salmon farming in Scotland)

Answer 4

1. Keeping the fish in cages - less energy used moving around; protects fish from interspecifc predation
2. Controlled diets of food pellets - high in protein to maximise growth, small quantities to prevent waste buildup
3. Young fish kept in separate, special containers; maximising survival rates by reducing intraspecific predation
4. Fishes kept in cages get diseases and parasites more often; like sea lice
   Rather than using pesticides that cause pollution, wrasse is used as a form of biological control - wrasse are insects that eat the lice off the salmon’s backs

Question 5

What do farmers do to farm fish in tanks?(Example - freshwater fish; carp)

Answer 5

1. Water can be monitored, checking for optimum temperature, pH and oxygen level
2. Food supply can be controlled, along with the type of food given
3. Water can be filtered and removed, to get rid of waste food and faeces - this keeps water clean and prevents pollution