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 |
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| Provides a reliable supply of food for a growing population | Waste and uneaten food pollute water and can cause eutrophication |
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| Reduces overfishing, which protects wild fish stocks and biodiversity | Disease and parasites can spread from farmed fish to wild fish |
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| Conditions can be controlled, so fish grow quickly | Escaped farmed fish may compete or interbreed with wild fish, reducing their genetic variety |
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| 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 Biology (1BI0) 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.
All 5 questions on Human impacts, biodiversity and food security
