Marine Aquaculture (Cambridge (CIE) IGCSE Environmental Management): Flashcards
Exam code: 0680
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Define overfishing.
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Define overfishing.
Overfishing is the harvesting of fish at a rate faster than they can reproduce, which causes population declines.
What drives the use of unsustainable harvesting practices at sea?
Rising global demand for seafood drives the use of unsustainable harvesting practices.
Define marine overharvesting.
Marine overharvesting is the excessive removal of marine organisms other than fish, such as shellfish, faster than they can naturally replace themselves.
True or False?
A target fish population recovers quickly as soon as fishing stops.
False.
Overfishing removes large, breeding adults, which reduces reproductive success and keeps recovery slow even after fishing stops.
Overfishing lowers the diversity of a target species, which makes it more vulnerable to disease and environmental change.
Overfishing lowers the genetic diversity of a target species, which makes it more vulnerable to disease and environmental change.
Define bycatch.
Bycatch is the species caught unintentionally during fishing, such as dolphins, turtles and seabirds.
Why does bycatch threaten populations of non-target species?
Bycatch threatens non-target populations because the animals caught often die in the nets or on the hooks.
What happens to prey populations when fishers overfish a predator species?
Prey populations can increase rapidly, which can lead to overgrazing of sea plants or overcrowding.
True or False?
Overfishing a prey species can cause the populations of its predators to fall.
True.
Predators have less to eat, so their populations may decline through starvation.
Why does overfishing make a marine ecosystem less stable?
Overfishing makes a marine ecosystem less stable because changes to predator-prey relationships cause cascading effects on many other species.
The loss of one key species through overfishing reduces overall marine .
The loss of one key species through overfishing reduces overall marine biodiversity.
Define marine aquaculture.
Marine aquaculture is the farming of marine species in captivity, under controlled conditions instead of catching them in the wild.
Why does seaweed farming need no added feed?
Seaweed farming needs no added feed because seaweeds absorb nutrients from the water as they grow.
Farmers can raise crustaceans such as prawns and shrimp in ponds or coastal .
Farmers can raise crustaceans such as prawns and shrimp in ponds or coastal enclosures.
True or False?
Seaweed farming supports only the food industry.
False.
Seaweed farming also supports the fertiliser and cosmetic industries.
How does marine aquaculture reduce pressure on wild fish stocks?
Marine aquaculture provides an alternative source of seafood, so less wild fishing takes place and wild populations can recover.
Why does aquaculture help make seafood more affordable?
Aquaculture helps make seafood more affordable because it provides a steady and predictable supply.
How can escaped farmed fish reduce the genetic diversity of wild fish?
Escaped farmed fish can interbreed with wild populations, which reduces genetic diversity and weakens their resilience.
True or False?
Keeping fish at high densities slows the spread of disease on fish farms.
False.
High densities make it easier for diseases and parasites to spread, and they can pass to wild fish if water flows between farms and the open sea.
Uneaten feed and fish waste raise the levels of nitrates and in the water beneath fish farms.
Uneaten feed and fish waste raise the levels of nitrates and phosphates in the water beneath fish farms.
Why do algal blooms caused by fish farm waste harm wild fish?
Algal blooms harm wild fish because decomposers use up oxygen as they break down the dead algae.
How does sediment build-up beneath fish cages affect the seabed?
Sediment build-up smothers seabed habitats, which reduces the biodiversity of seabed communities.
Why can the energy use of aquaculture increase carbon emissions?
Pumps, aeration and feeding systems need electricity, which increases carbon emissions when it comes from fossil fuels.
Fish cages attract wild predators such as birds and seals, which can increase human-animal .
Fish cages attract wild predators such as birds and seals, which can increase human-animal conflict.
Why can feeding carnivorous farmed fish increase fishing pressure?
Feed for carnivorous farmed fish often comes from wild-caught fish, which increases fishing pressure on smaller forage fish.
True or False?
Overuse of chemicals to control disease on fish farms can pollute the surrounding water.
True.
Farmers use antibiotics and other chemicals against disease, and overuse can pollute nearby waters.
How does an increased mesh size help maintain fish stocks?
A larger mesh lets juvenile fish escape, which gives them time to grow and reproduce.
Define fishing quota.
A fishing quota is a limit on how much of each species fishers can catch.
How do closed seasons protect fish populations?
Closed seasons stop fishing during breeding periods, which protects eggs, larvae and young fish so populations can grow.
True or False?
Pole and line fishing produces more bycatch than large trawling nets.
False.
Pole and line fishing targets individual fish, so fishers can release unwanted species, which reduces bycatch.
Define marine protected area (MPA).
A marine protected area is a zone where authorities restrict or ban fishing, so that it acts as a safe breeding ground.
Smaller boats have a lower fishing , which reduces the number of fish taken at once.
Smaller boats have a lower fishing capacity, which reduces the number of fish taken at once.
Why do countries need international agreements to manage fish stocks?
Countries need international agreements because many marine species migrate across international waters, so nations share the same stocks.
How do conservation laws discourage illegal fishing?
Conservation laws discourage illegal fishing through penalties, such as fines, boat seizures or bans on fishing licences.
True or False?
Fishing quotas can increase waste in marine ecosystems.
True.
Quotas can encourage fishers to discard unwanted catch to stay within their limits, which wastes fish and harms ecosystems.
How can political pressure weaken the conservation benefit of quotas?
Political pressure can push governments to set quotas too high, which reduces their conservation benefit.
Why can a limit on fishing days fail to cut the total catch?
A limit on fishing days can fail because fishers may increase their effort on the allowed days.
Pole and line fishing is slower and more -intensive than net fishing, so it may not meet high commercial demand.
Pole and line fishing is slower and more labour-intensive than net fishing, so it may not meet high commercial demand.
Why can marine protected areas cause conflict with local communities?
Marine protected areas can cause conflict because they restrict the fishing grounds that local fishers use.
What economic problem do closed seasons cause for fishers?
Closed seasons cause a loss of income for fishers during the closed period.
True or False?
A larger mesh size works just as well when fish populations are already severely depleted.
False.
A larger mesh is less effective if fish populations are already severely depleted.
Why are boat and net size limits hard to enforce?
Boat and net size limits are hard to enforce in areas with many small, unregistered or mobile vessels.
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