5.1.9Use of Biological Resources

Fish Farming — Edexcel International GCSE Biology 4BI1 Revision Notes & Topical Questions

5 min read 4 parts Lesson 5 of 7 Unit quiz

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Part 1 of 4Why Farm Fish?

Overfishing has reduced many wild fish stocks, and fish farms raise large numbers of fish in a small space as a source of protein.

Overfishing

Overfishing Catching wild fish faster than they can reproduce causes populations to fall, so farming reduces the pressure on wild stocks.

Control

Control The farmer controls feeding, water quality and predators, so growth is faster and more predictable than in the wild.

Cleaner fish

Cleaner fish Farmed fish can avoid pollutants such as mercury found in some wild-caught fish.

Disadvantage

Disadvantage Fish farming can be costly and labour intensive, and crowding increases the risk of disease and pollution.

Yield means the mass of healthy fish produced.

Water quality

Water quality Water is filtered and kept well oxygenated, so fish can respire aerobically and disease-causing bacteria are removed.

Intraspecific predation

Intraspecific predation Fish of the same species are sorted by size so larger fish do not eat smaller ones.

Interspecific predation

Interspecific predation Different species are kept apart using nets, fences or separate tanks to stop predators eating other fish.

Disease control

Disease control Antibiotics may be given and numbers limited, since infections spread quickly when fish are crowded together.

Waste removal

Waste removal Faeces and uneaten food are removed or flushed out, as waste can pollute the water and harm the fish.

Feeding and Breeding

Feeding

Feeding Fish are given food rich in protein and other nutrients, in small frequent amounts so little is wasted and fish do not fight over food.

Selective breeding

Selective breeding Individuals that grow fast, resist disease or have good flesh are chosen as parents, and their offspring inherit those alleles.

Over generations

Over generations Repeating selection over several generations gives a stock that grows faster and gives a higher yield.

Evaluation

Evaluation Benefits include a reliable food supply, but there are concerns about antibiotic use and waste polluting local waters.

Yield The mass of useful product obtained, such as the mass of fish harvested.
Overfishing Catching fish faster than the population can replace itself.
Intraspecific predation Predation of one organism by another of the same species.
Interspecific predation Predation by one species on a different species.
Selective breeding Choosing parents with desired characteristics to breed together.

Confusing intraspecific predation with interspecific predation; intra means within one species.
Saying antibiotics are given to make fish grow; in fish farms they are used to control disease.
Ignoring the drawbacks, such as cost, waste and disease risk in crowded fish.
Forgetting that selective breeding takes many generations to change a stock.

Last updated: 26 October 2026