Overfishing Flashcards
How has overfishing caused decreased populations of fish?
Nets with a small mesh catch fish before they’re sexually mature, so as time goes by there are less fish to reproduce.
What is drift netting?
When a net suspended by floats between two boats catches pelagic fish at the surface of water. It also catches other things like dolphins and turtles.
What is trawling?
A large net is dragged in the deeper water, catching the mid and bottom-feeders. Equipment used by trawlers damages the ocean bed.
How does overfishing affect other wildlife? (3)
- Trawlers catch capelin. Cod eat capelin. Less capelin causes cod stock to decline.
- Antarctic Krill have been harvested by 6 countries. They are the food for whales, penguins, seals etc. Heavy fishing of krill will affect the food web.
- Fishermen need to catch enough fish to make a living
Give 6 methods to regulate fishing.
- Larger mesh sizes.
- Quotas.
- Exclusion zones for some part of the year for fish to reproduce.
- Fish only eaten from sustainable sources.
- Legislation for fishing fleets and number of days at sea.
- Fish farming
FQ FELL
Explain what fish farming is.
Trout and salmon most popularly, are bred and grown to maturity in ponds, lakes, managed enclosures and moveable pods. They avoid predation and can have a maintained food supply.
Where do fish grow rapidly?
In warm waters discharged by factories.
Give 3 advantages of fish farming over pork/poultry/beef farming.
- Fish convert food to protein more efficiently
- Greater proportion of fish bodies are edible.
- Fish farming has a lower carbon footprint
Give 6 problems with fish farming.
- Diseased fish
- Escaped fish
- Pollution
- Resource use
- Environmental toxins
- Environmental degradation
DEEPER
Explain why diseased fish is a problem with fish farming.
- salmon are densely stocked so diseases transmit easily
- huge doses of antibiotics required
- pesticides used to control fish parasites damage things like molluscs
Explain why escaped fish is a problem with fish farming.
- farmed fish outcompete wild fish
- they transmit diseases and parasites
- they interbreed with wild fish and set up fast growing colonies which push wild fish to extinction
Explain how pollution is a problem with fish farming.
Eutrophication can occur from fish excreta, waste food and fertiliser.
Explain why resource use is a problem with fish farming.
Salmon eat 3 times their body weight in fish feed which is extremely inefficient.
Explain why environmental toxins are a problem with fish farming.
PCB’s, methyl mercury, dioxins and pesticides are more concentrated in farmed salmon than wild salmon.
Explain why environmental degradation is a problem with fish farming.
The shrimp industry especially had been blamed for the salinisation of soil and groundwater, and the destruction of mangroves which normally protect coastal communities from tropical storms.
