5.2 World fisheries

Question 1

Ocean structure

Answer 1

Continental shelf- shallowest part of a continental margin
continental slopes- where seafloor drops away quickly on edge of continental crust
continental rise- gentle slope at the base of continental slope
ocean floor

Question 2

Distribution of major fish populations are found in

Answer 2

They are found in shallow continental shelves

Question 3

Why continentental shelf can be rich in fisheries?

Answer 3

• it recieves more sunlight
• large abundance of oxygen
• large abundance of phytoplankton
• Abundance of CO2 for phtotsynthesis by phytoplankton
• Due to phaytoplankton on continental shelf it means abundance of food

Question 4

Surface currents

Answer 4

movement of the surface water of the sea in a constant direction.

Question 5

Warm ocean currents-

Answer 5

warm water is moving from the tropics towards poles

Question 6

Cold ocean current-

Answer 6

water from colder areas is moving from poles towards the equator.

Question 7

Prevailing wind:

Answer 7

the direction from which the wind nearly always blows in a particular area.

Question 8

Circulation of ocean currents in north of the equator

Answer 8

current circulations are mainly clockwise.

Question 9

Circulation of ocean currents in south of the equator

Answer 9

South of equator, the circulation of currents in all three oceans ( Pacific, Indian, Antarctic) is mainly anticlockwise.

Question 10

example of cold current

Answer 10

peru current (beside S USA)
west australia current

Question 11

example of warm current

Answer 11

South equatorial current
east australia current

Question 12

factors affecting ocean currents

Answer 12

1) temperature of water
2) prevailing winds
3) rotation of earth (due to rotation, currents move clockwise in north hemisphere, anticlockwise in southern hemisphere)
4) Salinity of water: higher the salinity warmer the currents

Question 13

Upwelling

Answer 13

• areas where minerals at the ocean floor (cold current) are brought up to the surface by currents.
• This layer is rich in nutrients which results in higher productivity
  KEY TERMS- cold currents, upwelling, more nutrients, more phytoplanktons, more fishes

Question 14

Downwelling

Answer 14

is where surface water (warm currents) is forced downwards, where it may deliver oxygen to deep water, downwelling leads to reduced productivity, as it extends the depth of nutrient-limited layer
KEYTERMS- Warm currents, downwelling, less nutrients, less phytoplanktons, less fishes

Question 15

effect on climate of cold currents-

Answer 15

cold and dry, drought,
fog and mist

Question 16

effect on climate of warm currents-

Answer 16

warm and heavy rainfall

Question 17

El Niño Southern Oscillation (ENSO) meaning:

Answer 17

the change in the prevailing winds that leads to change in the pattern of currents in the oceans of the South Pacific.

Question 18

Effect of EL Nino southern oscillation (ENSO):

Answer 18

• Warm nutrient-poor water comes into the region from the equator.
• Results in no upwelling of the cold, nutrient-rich water that supports the anchovy fishery(Peruvian).
• No nutrients mean the phytoplankton do not grow well, so there’s less food for the fish, resulting in fewer fisheries as they migrate somewhere else
• The effects of El-Nino include the reversal of wind patterns across the Pacific, drought in Australia, and unseasonal heavy rain in South America.
• Much of the production of the anchovy fishery was used for fishmeal which is used to feed farmed fish, thus countries where this is important, are affected by a crash in the anchovy fishery.