AQA Biology 4.7.5.3 · Triple only
Sustainable fisheries
A fish stock is a breeding population. Catch too many, or catch them too young, and there is nothing to breed next year. Two levers bring it back.
Triple Science · Higher tier
Start here
Empty the pond.
You catch every fish in a pond, including the babies.
If you had to guess, will there be fish in the pond next year, or none?
The problem
Declining stocks.
Fish stocks in the oceans are declining. Fish is an important source of protein for billions of people. It is important to maintain fish stocks at a level where breeding continues, or certain species may disappear altogether in some areas. Tap each.
Two levers
Quotas and net size.
Control of net size and the introduction of fishing quotas play important roles in conservation of fish stocks at a sustainable level. Set the two levers and watch one stock over twenty years. The numbers are made up.
No quota: the catch takes more than the stock can replace. Small mesh: young fish are caught before they can breed. After 20 years the stock is 3% of where it began. Below the line, too few are left to breed: collapse.
Why does a larger mesh help the stock recover?
Pick one.
Use the data
Explain the recovery.
Information · made-up data for practice
A cod stock (made up): 1990, 250 000 tonnes; 1995, 150 000; 2000, 60 000. A quota and a larger minimum mesh size were introduced in 2001. 2005, 70 000; 2010, 110 000; 2015, 160 000.
Use the data: how did the measures help the stock recover?
Pick one.
Why did the stock take years, not months, to recover?
Pick one.
Think again · back in a year?
“Stop fishing for a year and the stock is back.”
Your call
ChooseA stock has collapsed. Fishing stops. How long does recovery take?
Sort
Helps or harms?
Place each action.
Tap a card, then tap the box it belongs in. Tap a placed card to take it back.
Command words in this lesson
- Explain
- How net size and quotas keep a stock at a sustainable level.
- Describe
- Why fish stocks are declining and what sustainable means.
- Use the data
- To relate a change in stock to a measure introduced.
Key fact
A sustainable stock is one where breeding continues. Quotas limit how many fish are taken each year, set from population estimates. A larger mesh lets young fish escape to grow and breed. Recovery takes as long as the fish take to reach breeding age.
Key note · AQA 4.7.5.3 (Biology only)
Sustainable fisheries
- Fish stocks in the oceans are declining. It is important to maintain fish stocks at a level where breeding continues or certain species may disappear altogether in some areas.
- Control of net size and the introduction of fishing quotas play important roles in conservation of fish stocks at a sustainable level.
- Quotas: a limit on the catch each year, agreed between countries on scientific advice from population estimates.
- Mesh size: a larger minimum mesh lets young fish escape to grow and breed.
- Use a stock graph: quote the values, name when the measure began, link the change to breeding, and remember recovery takes years.
Photograph this card. Tomorrow, cover it and say each line first.
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Ask MrBadmus
Thinking small-mesh nets are better because they catch more?
The stock figures and years are made up for practice.