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AQA Environmental science questions > Aquatic food resources > Flashcards

Aquatic food resources Flashcards

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1
Q

What are the main fishing methods?

A

Demersal fishing
Shellfish traps
Pelagic fishing

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1
Q

What does demersal fishing include?

A

Fishing for species that live on the seabed

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2
Q

2 types of demersal fishing

A

Demersal trawling
Demersal lng lines

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3
Q

demersal trawling

A

Used for species on the seabed
E.g. cod,haddock,plaice,shrimps,scampi

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4
Q

Demersal long lines

A

Uses a line of baited hooks to catch species such as cod and haddock

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5
Q

Shellfish traps

A

Baited traps to catch crustaceans like crabs,crayfish and lobsters

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6
Q

What is pelagic fishing?

A

It includes fishing for species that live in open water above the seabed, often near water surface

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7
Q

4 types of pelagic fishing

A

Pelagic trawling
Drift nets
Purse seining
Pelagic long lines

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8
Q

Pelagic trawling

A

Used for species that form shoals in mid water or near the surface
E.g. bass, anchovies, herrings, mackerels

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9
Q

What is the advantage of pelagic trawling?

A

Pelagic fish are often in single species shoals
Little chance of catching non-target species except predator species e.g. dolphins

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10
Q

Drift nets

A

Long curtain like nets supported by floats and catch pelagic species near the surface line tuna and herring

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11
Q

Purse seining

A

Uses a net laid round a shoal
Top is held by floats
The bottom is held by weights, then pulled tight underneath the shoal
Used for tuna, sardines,herring and anchovies

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12
Q

Pelagic long lines

A

Lines of baited hooks which can be many Km in length
Catch species like tuna and squid

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13
Q

4 main types of environmental impacts of fishing

A

Population decline due to overfishing
Bycatch
Ghost fishing
Habitat damage

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14
Q

How can overfishing cause population decline?

A

Population of any species will decline if the mortality rate exceeds the birth rate
K-selected species are most vulnerable to overfishing-fewer young at older age
Some species reach a catchable size before they reach sexual maturity, so overfishing could remove the entire breeding population

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15
Q

What species of fish recover quicker from overfishing?

A

R-selected species because they breed at a younger age and produce more young
The populations recover more rapidly after over-fishing
E.g. herring, yellow fin tuna

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16
Q

Give an example of a species that is vulnerable to overfishing

A

Greenland shark
It was fished commercially for lubricating and lamp oil until the 1960s
Main threat now is deep-sea trawling bycatch
It can live over 400 years, doesnt start breeding until 100-150 years and it produces few young

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17
Q

Impact of over-exploited local fisheries on countries like the UK

A

It will still be maintained by exploited fisheries just further away

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18
Q

What is bycatch ?

A

The catch that is not wanted
Usually non-target species included in the catch of target species, or individuals too small to be legally sold.

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19
Q

Give 3 reasons why bycatch might be unwanted

A

Immature fish- too small to sell, will affect future catches
If the catch quota for a species has already been reached- must be discarder
Species with no commercial value

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20
Q

What impact does bycatch have, on the organisms in the bycatch?

A

They are usually dead or will be injured and not survive when they are thrown back into the sea

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21
Q

Compare the bycatch from different fishing methods

A

Purse seine nets/pelagic trawling have a lower bycatch usually than demersal trawling
Demersal trawling usually exploits mixed fisheries

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22
Q

Drift net bycatch

A

They are non selective and will catch any animals swimming near the surface including whales,dolphins,turtles and sharks

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23
Q

Pelagic long line fishing

A

Albatrosses are large seabirds that collect food near the water surface
They are usually caught by long line fishing and drown because of it
They have a low reproduction rate, and lay one egg every second year, but it takes 7-10 years before they start breeding
So populations can be seriously effected

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24
Q

Pelagic trawling bycatch

A

Pelagic pair trawls for sea bass can kill porpoises
Because the porpoises are trying to catch the bass but get trapped in the nets and drown

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25
Q

Demersal trawling bycatch

A

Seabed fish often live in mixed-species shoals so the chance of catching a mixture of species is high

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26
Q

Shrimp bycatch

A

Shrimp use trawling nets with very small mesh size so few bycatch animals can escape
E.g. crabs,molluscs,sea urchins,starfish
Can make up to 99% of shrimp trawling

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27
Q

What is ghost fishing?

A

When discarded or lost fishing gear can continue to trap and kill marine organisms
Dead organisms that are trapped often act as bright so more organisms get caught and die

28
Q

5 ways habitats can be damaged by fishing

A

1) Seabed damage
2) Coral reef impact
3) Seagrass beds
4) Dynamite fishing
5) Food web impacts

29
Q

What type of fishing causes the most damage to the seabed?

A

Demersal trawling

30
Q

Impact of seabed damage

A

Loss of marine habitat

31
Q

Coral reef impact

A

coral is highly sensitive to physical damage. Nets, traps, ropes and discarded gear can all cause physical damage.

32
Q

Impact of dynamite fishing

A

Explosives used in blast fishing not only kill fish but also destroy coral skeletons, creating unbalanced coral rubble

33
Q

When might dynamite fishing be used?

A

It aims to stun and kill a school of fish or other commercial species by blasting dynamite and collecting them easily. It is mosty used in in developing or undeveloped areas of the world.

34
Q

4 ways the environmental impacts can be reduced

A

Catch quotas
Fishing equipment design and use
Restricting fishing Effort
Restricting fishing methods

35
Q

What is the purpose of a catch quota?

A

To set a limit of the total weight of fish that can be landed
It might be divided up between all fishing boats in a fleet

36
Q

When do catch Quito’s not work/are less effective?

A

In mixed fisheries when different fish are caught in the same net
If the catch quota for one species has been reached, surplus may be returned to the ocean whilst fishing for the other species continues
The surplus are likely o be returned dead or injured

37
Q

Give 9 ways fishing equipment designs and uses can be changed to reduce the environmental impacts of fishing

A

Mesh size
Mesh design
Escape panels acoustic deterrent devices
Hook shape
Decoys
Sinkers
Night fishing
Biodegradable/radiotracked equipment

38
Q

How can mesh size be altered to reduce the environmental impacts of fishing?

A

They can be set so that fish below a certain size can escape

39
Q

How can hook shape be altered to reduce the environmental impacts of fishing?

A

Longline hooks have curved points
Still catch tuna but less likely to catch albatrosses

40
Q

Escape panels

A

Turtle exclusion devices
Large spring loaded escape panels in the nets that allow turtles to escape

41
Q

Acoustic deterrent devices

A

Also known as ‘dolphin pingers’
Produce high frequency sounds that warn dolphins about the presents of the net

42
Q

Decoys

A

They attract and distract birds so they dont get caught on longline hooks

43
Q

Sinkers

A

Weights attached to pelagic longlines
They hold hooks down in the water so they still catch fish but not albatrosses

44
Q

Night fishing

A

Using longlines at night when birds aren’t feeding

45
Q

Biodegradable and radio tracked equipment

A

Reduces ghost fishing
Traps for crabs and lobsters, if they are held together by biodegradable rope, will fall apart if lost so wont continue to catch organisms
In the USA traps have radio-transmitters that activate if the traps are lost so they can be recovered

46
Q

How might the fishing effort be restricted in order to reduce the environmental impacts of fishing?

A

In some areas of the UK there are limits of the size and power of fishing boats, and no of days they can spend fishing
Where the number of fishing boats is so large that overfishing is unavoidable, boat owners may receive compensation for their boats to be decommissioned

47
Q

9 ways fishing methods are/can be restricted

A

Ban drifts nets
Bans on demersal trawling
No take zones
Turtle bycatch
Closed-seasons
Minimum and maximum catchable size
Protected individuals
Captive rearing and release

48
Q

Where might demersal trawling be banned?

A

in areas where the seabed ecosystem is particularly sensitive or important.

49
Q

No take zones

A

areas where fishing and other activities that exploit wildlife or damage the habitat are not permitted. Protecting the breeding populations of breeding adults so a population can recover.

50
Q

How can turtle bycatch be reduced?

A
  • reducing the time that the net is towed can reduce bycatch mortality
51
Q

Closed seasons

A

a ban on fishing for part of the year allows the fish to grow to a larger size

52
Q

Minimum catchable size
Maximum catchable size

A

allows large numbers of small fish to grow to a larger size and live long enough to breed. Protecting large individuals may ensure there is a surving population

53
Q

Captive rearing and release, or ‘population seeding’

A

increasing the wild populations of some species by releasing individuals that have been raised in captivity.

54
Q

the natural breeding rate exceeds the necessary to sustain the population. why will a breeding surplus not increase the long term adult population?

A

surplus individulas will die because the carrying capacity of the environment has been exceeded

55
Q

what will increase in a population where the carrying capacity of an environment has been exceeded?

A

density dependent factors which will increase mortality rate
e.g. intraspecific competition for food

56
Q

what is the MSY for a fish population?

A

the greatest biomass that can be removed from the population each year without the population suffering long term decline

57
Q

Why are Freshwater areas so productive?

A

Water bodies on land are very productive as they receive nutrient run off from the land and receive high light levels because they are relatively shallow

58
Q

Trawling often results in high by-catch.
Describe how one change in net design and one change in fishing method can
reduce by-catch. (2 marks)

A

Net Design: increased mesh size allows smaller fish to escape
Fishing method: fishing at night so seabirds cannot see catch OR longline uses specific hook shapes/bait

59
Q

Describe two other environmental impacts of trawling. (2 marks)

A

habitat damage/ named eg (from direct contact with nets)
ghost fishing (from discarded equipment)

60
Q

Suggest reasons for the changes in the catch of lobsters shown in Figure 2 (Dramatic decrease)

A

Up to two marks for explanation before 1997:
fishing below MSY/appropriate quotas set
increased fishing effort/technology
Up to three marks for cause of population decline after 1997:
overfishing/fishing above MSY
quotas set too high
net mesh too small

61
Q

Describe how scientists could collect data to estimate the lobster population without
the use of trawling.

A

shellfish/lobster trap
Three from:
* captured individuals are marked and released
* second set of traps placed/recapture
* leave for a length of time to allow

62
Q

name one abiotic factor and one biotic factor that
would need to be controlled in this investigation to find the relationship between the temperature of water and the growth rate of fish.

A

Abiotic: PH of water, extreme acidity/alkalinity leads to slower growth rate due to impact on enzyme and activity

Biotic: Age of fish, younger fish have a much faster growth rate than older individuals

63
Q

Explain why primary productivity varies between open oceans and continental
shelves.

A
  • nutrients at surface on continental shelf due to disturbance of
    seabed/ runoff from land
  • less nutrients near surface in open oceans because DOM sinks
64
Q

Discuss how the environmental impacts of aquaculture may be reduced. [25 marks]

A

impacts of predator control/culling
methods to reduce predator control/culling
e.g.
better cage design
sterile fish
avoid non-indigenous species with potential to be invasive
impacts of using pesticides to kill lice/ antibiotics
methods to reduce the use of pesticides to kill lice/ antibiotics
e.g.
using cleaner fish e.g. wrasse/ lumpsuckers
removing excessive growth of weed and crustaceans by
mechanical cleaning of cages
reduce stocking density
vaccinations/ breed in disease resistance
tanks with single age group
overfishing/fish impacts of feed production
methods to reduce overfishing/fish impacts of feed production
e.g.
farming herbivorous fish
plant based protein feed pellets
control feed waste by CCTV/ laser shut off

65
Q

Suggest why fish farmers use polyculture instead of monoculture. (2 marks)

A

Higher productivity/higher
yield per unit area
some species provide
faeces/food for
others/common carp

66
Q

Suggest why fish farmers add manure to polyculture lakes. (2 marks)

A

to replace nutrients
removed by fishing
cheaper/more easily
available than inorganic
fertiliser

67
Q

Describe two ways that wastes from aquaculture may reduce local water quality.
[4 marks]

A

faeces
hormones

68
Q

Discuss the advantages and disadvantages of the methods used to reduce the
environmental impacts of fishing.
[25 marks]

A

AQA Environmental science questions (8 decks)

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