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
Section 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
- Catching wild fish faster than they can reproduce causes populations to fall, so farming reduces the pressure on wild stocks.
Control
- The farmer controls feeding, water quality and predators, so growth is faster and more predictable than in the wild.
Cleaner fish
- Farmed fish can avoid pollutants such as mercury found in some wild-caught fish.
Disadvantage
- Fish farming can be costly and labour intensive, and crowding increases the risk of disease and pollution.
Section 2 of 4Methods Used to Increase Yield
Yield means the mass of healthy fish produced.
Water quality
- Water is filtered and kept well oxygenated, so fish can respire aerobically and disease-causing bacteria are removed.
Intraspecific predation
- Fish of the same species are sorted by size so larger fish do not eat smaller ones.
Interspecific predation
- Different species are kept apart using nets, fences or separate tanks to stop predators eating other fish.
Disease control
- Antibiotics may be given and numbers limited, since infections spread quickly when fish are crowded together.
Waste removal
- Faeces and uneaten food are removed or flushed out, as waste can pollute the water and harm the fish.
Section 3 of 4Feeding and Breeding
Feeding and Breeding
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
- Individuals that grow fast, resist disease or have good flesh are chosen as parents, and their offspring inherit those alleles.
Over generations
- Repeating selection over several generations gives a stock that grows faster and gives a higher yield.
Evaluation
- Benefits include a reliable food supply, but there are concerns about antibiotic use and waste polluting local waters.
Section 4 of 4Exam Checklist & Tips
5.1.9 – Key Points for the Exam
- 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.
Common Mistakes
- 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.
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