4.3 aquatic food production systems

Question 1

range and productivity of aquatic ecosystems

Answer 1

dominant source of primary productivity: phytoplankton –> single-celled photosynthetic organisms

Question 2

faroe whale hunting (faroe islands)

Answer 2

• average of 800 whales killed annually

reasons for:
- important part of culture and history
- natural source of food

reasons against:
- cruel –> kills with spears = painful
- meat contains mercury health risks

Question 3

marine food chain

Answer 3

• longer + more complex than terrestrial ecosystems
• more energy transmitted up food chain

Question 4

demand for aquatic food resources

Answer 4

• demand increases
• increase in population
• more money = more protein
• perception of fish as healthy

Question 5

we’re catching more fish because…

Answer 5

improvements in technology
- change from stail to steam
- refrigeration
- fish-finders: GPS

Question 6

bottom trawling

Answer 6

• dragging weighted net along seafloor to catch bottom-dwelling species (lobster, shrimp)
• results in damage to seafloor habitats
• high bycatch

Question 7

dredging

Answer 7

• uses rake-like structure dragged across seafloor to harvest shellfish, clams, and mussels
• results in damage to seafloor habitats
• bycatch is low

Question 8

gillnets

Answer 8

• vertical panels of netting set up as walls with openings to allow fish to get their heads through but not their bodies
• used to catch salmon –> other marine mammals (sea turtles) can be caught
• high bycatch because it drifts with the current and isn’t anchored

Question 9

marine reserves (florida)

Answer 9

• “no take zones”
• effective at creating mature fish and protecting env. from fishing damage
• terminal impact on fisheries who traditionally fished

Question 10

closed seasons (australia cuttlefish)

Answer 10

• no catch allowed during breeding season or other critical times
• economic impact

Question 11

changing consumer behaviour - grand banks, canada (ineffective)

Answer 11

what was happening
- “inexhaustible” stock –> now have technology
- 1958-1977: catches reached all-time highs

what was done
- too late to control overfishing
- 90s: cod population collapsed

what it caused
- cod stock still not recovered over 25 years later
- loss of jobs

Question 12

changing consumer behaviour - iceland (effective)

Answer 12

• focus on scientific research –> “marine research institute”
• total allowable catch
• licensing of boats –> each allocated a quota

Question 13

why it’s hard to change consumer behaviour

Answer 13

• consumers are lazy / disinterested
• labeling of seafood –> difficult to understand
• people may buy purely on economic grounds

Question 14

salmon farming in scotland

Answer 14

inputs:
- high density of fish enables disease spread

processes:
- high mortality rates (9.5 million fish annually)
- animal welfare concerns

outputs:
- diseases spread to wild populations
- genetic disruption

Question 15

seaweed farming

Answer 15

inputs
- seaweed improves quality of water by absorbing pollutants

processes
- invasive species can overgrow and take over coral reefs

outputs
- seaweed doesn’t require fertiliser, pesticides, or freshwater