AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
It is important to maintain fish stocks at a level where breeding continues…
Full specification wording
Sustainable fisheries: It is important to maintain fish stocks at a level where breeding continues or certain species may disappear altogether in some areas.
A fish stock must be kept above a minimum size so that enough adult fish survive to breed successfully.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 2 of 3
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A fish stock must be kept above a minimum size so that enough adult fish survive to breed successfully. If too many adults are removed, the remaining population may be too small or too spread out to find mates and spawn. Over time, the number of young fish falls, and the population cannot replace the fish that are caught. If this continues, the species may become locally extinct, meaning it disappears from that area even if it survives elsewhere. Maintaining stocks at a sustainable level means leaving enough breeding adults to produce the next generation.
For example: If fishing removes most large adult cod before they can spawn, recruitment of young cod collapses and the local stock may disappear.
What earns the marks
- State that fish stocks must be kept at a level where enough adult fish survive to breed.
- Explain that breeding continues only if the breeding population is large enough to find mates and spawn successfully.
- Describe how removing too many adults reduces the number of young fish produced.
- Explain that continued overfishing can cause a species to disappear from a particular area.
- Recognise that local disappearance may occur even if the species still exists in other areas.
Common mistakes and how to put them right
Thinking that a species disappears everywhere at once.
Put it right: Local extinction means it is lost from one area, not necessarily globally.
Believing that breeding can continue normally even when very few adults remain.
Put it right: Small, scattered populations may fail to reproduce successfully.
Confusing the number of fish caught with the number of breeding adults left.
Put it right: It is the surviving breeding population that determines future recruitment.
Exam tips
- Use the term ‘breeding population’ when explaining why a minimum stock level matters.
- Distinguish between local disappearance and global extinction if the question asks about ‘some areas’.
- Link the idea of sustainable stock size to the survival of the next generation.
Try the lesson
The start of the Sustainable fisheries: It is important to maintain fish stocks at a level where breeding continues or certain species may disappear altogether in some areas. lesson, made from checked teaching notes for this specification point.
Have a go first
Why is it important to keep fish stocks at a level where breeding can continue?
Listen
A fish stock must be kept above a minimum size so that enough adult fish survive to breed successfully. If too many adults are removed, the remaining population may be too small or too spread out to find mates and spawn. Over time, the number of young fish falls, and the population cannot replace the fish that are caught. If this continues, the species may become locally extinct, meaning it disappears from that area even if it survives elsewhere. Maintaining stocks at a sustainable level means leaving enough breeding adults to produce the next generation. For example, if fishing removes most large adult cod before they can spawn, recruitment of young cod collapses and the local stock may disappear. A strong answer earns marks for these points. State that fish stocks must be kept at a level where enough adult fish survive to breed. Explain that breeding continues only if the breeding population is large enough to find mates and spawn successfully. Describe how removing too many adults reduces the number of young fish produced. Explain that continued overfishing can cause a species to disappear from a particular area. Exam tip: Use the term ‘breeding population’ when explaining why a minimum stock level matters.
Key words
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Local extinction
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Sustainable level
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Breeding population
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Recruitment
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See every definition
- Local extinction
- When a species disappears from a particular area, even if it survives elsewhere.
- Sustainable level
- Maintaining stocks by leaving enough breeding adults to produce the next generation.
- Breeding population
- The surviving adults, which must be large enough to find mates and spawn successfully.
- Recruitment
- The production of young fish, which collapses if fishing removes most large adults before they can spawn.
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