Fishing And Aquaculture

Question 1

Light levels

Answer 1

Photic zone - most light near water surface
Aphotic zone - little light and deep

Question 2

Nutrients

Answer 2

• algae absorb nutrients in water and photosynthesise
• phosphates low solubility causing deficits
• ## high phosphates in photic due to runoff and areas of cold water upwelling

Question 3

How does light and growth change in tropical areas?

Answer 3

• high light, warm temp all year
• low nutrients all year

Question 4

How does productivity and. Nutrients change in temperate oceans?

Answer 4

• high productivity with light peaks
• drops when nutrients declines in winter
• autumn storms disturb sediment and cause bloom .

Question 5

Antarctic Ocean

Answer 5

• low water temp all year,
• light drops with growth middle of year
• ## storms and upwelling increases nutrients

Question 6

Fresh water

Answer 6

Highly productive due to runoff
High light

Question 7

Coastal area

Answer 7

Nutrients high from runoff and coastal u9owelling
High light and temp

Question 8

Explain wind driven currents

Answer 8

• wind blows over ocean surface
• water pulled up
• warm water towards poles
• cold water towards equator
• earth spins so doesn’t flow straight and deflected into gyres.
• this deflection = coriolis effect

Question 9

Describe thermohaline currents

Answer 9

• driven by temperature changes and salinatiy
• both affect water density and trigger rising or sinking forming currents
• slower than wind
• all currents for one big loop called thermohaline circulation or global conveyor belt

Question 10

3 key words of ocean zones

Answer 10

benthic = bottom
Demersal = above seabed
Pelagic = water column

Question 11

Fishing methods: pelagic trawling

Answer 11

• net dragged along open water behind boat, to catch shoals of anchovies and mackerel
• low non-target species capture
• possible bycatch but lots of fish in one go
• fuel used when boat is looking for shoal
• easy to overfish

Question 12

Fishing methods: demersal (bottom) trawling

Answer 12

• dragged on sea floor
• exploited mixed fisheries due to high biodiversity caught.
• towing resistance and friction uses up energy
• significant habitat damage and bycatch

Question 13

Fishing methods: purse seining

Answer 13

• Curtain nets around a shoal And closed underneath
• pelagic species in shoals so less bycatch
• tightening of net reduces escapes
• resistance of lifting net increase energy use

Question 14

Fishing methods: drift netting

Answer 14

• curtain net dragged behind boat , weights and boys
• fish swim into it and get stuck by their gills
• bycatch is high
• lower energy use due to static process.

Question 15

Fishing methods: long lining

Answer 15

• hooks with bait on a line
• limited bycatch
• catch albatross
• static passive process

Question 16

Fishing methods: shellfish trapping

Answer 16

• baited cages