Fish farming

Ecosystems and material cycles · Human impacts, biodiversity and food security · note 1 of 4

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Fish farmingSpec 9.9

In short

Fish farming is a human interaction with ecosystems that has positive and negative impacts on biodiversity. It provides a reliable food supply and reduces overfishing of wild fish stocks. However, waste and uneaten food can cause eutrophication, disease and parasites can spread to wild fish, and escaped fish may compete or interbreed with wild fish.

Human interactions with ecosystems can have both positive and negative impacts on biodiversity, which is the variety of living organisms in an ecosystem. Fish farming is one example.

Fish farming: positive and negative effects
Positive	Negative
Provides a reliable supply of food for a growing population	Waste and uneaten food pollute water and can cause eutrophication
Reduces overfishing, which protects wild fish stocks and biodiversity	Disease and parasites can spread from farmed fish to wild fish
Conditions can be controlled, so fish grow quickly	Escaped farmed fish may compete or interbreed with wild fish, reducing their genetic variety
	Fish may be fed on wild fish, and chemicals used to control disease can harm other organisms

Exam tip:

For an evaluation, give at least one positive and one negative, and then say which you think outweighs the other and why.

Written and checked against the Edexcel GCSE Combined Science (1SC0) specification · Updated October 2026

Frequently asked questions

What is eutrophication and what causes it?

Eutrophication is caused by too many nutrients, such as nitrates from fertilisers or sewage, running into lakes and rivers. Algae grow quickly and block light, so plants below die. Decomposer bacteria feed on the dead material and use up the oxygen for aerobic respiration, so fish and other aquatic animals die and biodiversity falls.

Why is biodiversity important to ecosystems?

Biodiversity is important because ecosystems with high biodiversity are more stable. Species depend on each other, so the loss of one is less likely to cause others to fail. Biodiversity also gives humans food, materials and medicines, and species help maintain the conditions we depend on, such as pollination of crops and cycling of materials.

What are the advantages and disadvantages of fish farming?

Fish farming provides a reliable food supply, reduces overfishing of wild stocks, and lets conditions be controlled so fish grow quickly. However, waste and uneaten food pollute water and can cause eutrophication, disease and parasites can spread to wild fish, and escaped fish may compete or interbreed with wild fish, reducing their genetic variety.

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