fishing

Question 1

what is meant by marine productivity

Answer 1

the amount of food that can be harvested- limited by factors such as light and nutrients

Question 2

list the different types of fishing methods

Answer 2

1) Demersal- fishing for species that live on the sea bed

2) pelagic- fishing for species that live in the open waters above the sea bed, often near the surface of waters

Question 3

outline demersal trawling

Answer 3

• used for species on the seabed such as cod or haddock

- involves the dragging or a weighted net along the sea bed which catches fish in its path

Question 4

what are the disadvantages of demersal trawling

Answer 4

• high bycatch
• disturbed habitat on the sea bed
• increased turbidity from dislodged sand particles
• decarded nets allow ghost fishing

Question 5

outline demersal long lines

Answer 5

• the use of a long line with baited hooks which catch species such as cod and haddock
• the hooks can be made a specific shape complementary to a certain species gills reducing by catch

Question 6

outline pelagic trawling

Answer 6

• used for species which form shoals in mid-water or near the surface such as bass
• a net is hung between two boats and dragged through the water collected fish in the shoal s

Question 7

compare by catch rates of demersal and pelagic trawling

Answer 7

pelagic- pelagic fish tend to form single species shoals so the catch of non-target species is usually low but predator species may also be caught such as dolphins

demersal- higher bycatch rate

Question 8

outline drift nets as a form of pelagic fishing

Answer 8

• long curtain-like nets which are supported by floats and catch pelagic species near the surface
• nets can be kilometres long

Question 9

outline purse seining

Answer 9

• a net is laid around a shoal of fish

- the top is supported by floats while the bottom is held by weights the pulled tight underneath the shoal

Question 10

outline pelagic long lines

Answer 10

lines of baited hooks which may be kilometers in length which catch species in mid or surface waters such as tuna or squid

Question 11

list the environmental impacts of fishing

Answer 11

1) Bycatch
2) population decline
3) Ghost fishing
4) habitat damage

Question 12

what is bycatch

Answer 12

the non-target organisms which are caught when fishing such as

• immature fish too small to sell
• individuals of a catch quota that has already been filled
• species with no commercial value
  many species will be returned too injured to survive of be dead already
  amount of bycatch depends on fishing methods

Question 13

outline drift net bycatch

Answer 13

• the catch of species near swimming near the surface such as dolphins

Question 14

what is ghost fishing

Answer 14

fishing gear that has been disregarded or lost may continue to trap and kill marine organisms
dead organisms caught act as bait attracting more individuals who also become trapped and die

Question 15

list the forms of habitat damage

Answer 15

1) sea bead damage
2) coral reef impact
3) seagrass beds
4) dynamite fishing
5) food web impacts

Question 16

outline sea bed damage and coral reef impact

Answer 16

1) demersal trawling nets often have metal balls to disturb the sea bed mixing shallow aerobic surface layers with deeper anaerobic layers as well as destroying slow-growing organisms
2) coral polyps are sensitive to physical damage so can be killed if pressed against the cup they are attached

Question 17

outline habitat damage to seagrass beds

Answer 17

• grass-like plants on shallow sandy areas which act as an important nursery ground for many species in coral reefs of deep water
• disturbance from trawling kills plants so roots no longer bind sand so currents move sand around

Question 18

outline dynamite fishing

Answer 18

pressure waves released by underwater explosions stun fish making them easier to catch
commonly used in coral reefs where nets cant be used but explosions kill coral and other organisms

Question 19

outline food web impacts

Answer 19

reducing the number of species will cause

• increased competitors
• increased prey
• predators may become rarer

Question 20

why might population decline

Answer 20

• if mortality exceeds birth rate species are likely to become overfished
• K select species are more vulnerable to overfishing as they produce fewer young and reach sexual maturity ad a later age
• R select species populations are lily to recover faster