Aquatic food production systems

Question 1

Why do marine ecosystems have high stability and resistance?

Answer 1

Marine ecosystems are usually very biodiverse and so have high stability and resilience

Question 2

What is the continental shelf?

Answer 2

An extension of continents under the ocean. Where continental shelf exists it creates shallow water

Question 3

Why is the continental shelf important?

Answer 3

• it has 50% of oceanic productivity but just 15% of its area
• upwellings bring nutrient-rich water up to the continental shelf
• light reaches the shallow seas so producers can photosynthesise
• countries can claim it as their to exploit + harvest

Question 4

What are phytoplankton and why are they so important? What about zooplankton?

Answer 4

PHYTOPLANKTON

• single-celled organisms
• can photosynthesise
• produce 99% of primary productivity
• they float in sea

ZOOPLANKTON

• float in sea
• single-celled organisms
• eat phytoplankton and their waste

Question 5

Marine ecosystems can be classified as:

Answer 5

BENTHIC // living on or in the sea bed

PELAGIC // living surrounded by water from above the sea bed to the surface

Question 6

What is a fishery?

Answer 6

A fishery exists when fish are harvested in some way. It includes capture of wild fish and aquaculture (fish farming)

Question 7

What percentage of fishery activity is in oceans?

Answer 7

90%

Question 8

How many people make a livelihood in fisheries?

Answer 8

Up to half a billion people

Question 9

How many people gain 20% of their protein intake from fish

Answer 9

3 billion

Question 10

Health benefits of fish

Answer 10

• high in protein
• low in sat. fat
• contain vitamins A,B,D needed for healthy diet

Question 11

What percentage of the world’s fisheries are fully exploited, seriously depleted or too low to allow recovery?

Answer 11

70%

Question 12

What is aquaculture?

Answer 12

The farming of aquatic organisms in both coastal and inland areas involving interventions in the rearing process to enhance production

Question 13

On average, how much fish and meat does a person eat per year?

Answer 13

• On average worldwide, each person eats about 20kg of fish + 8kg of meat per year
• This used to be higher for meat and lower for fish
• Diets are changing as need to reduce sat fat is understood
• Most extra fish is coming from farms

Question 14

Why does most of the extra fish come from fish farms?

Answer 14

• Although technology has improved, wild caught fishing has reached its limit
• Either they are not there due to overexploitation
• Or we cannot take more than sustainable yield + that is not enough as human pop. grows

Question 15

Name 3 ways fish farming is becoming more sustainable

Answer 15

> Fishmeal uses more trimmings + scraps that would have been wasted in past
Livestock + poultry processing waste is substituted for fishmeal
8 species of carnivorous fish (inc. Atlantic salmon) can get enough protein w/o eating other fish

Question 16

What percentage of all farmed fish is produced by China and why is this so important for Chinese farmers?

Answer 16

• China produces 62% of all farmed fish worldwide
• Fish grown in rice paddies + their waste provides fertiliser for the rice
• System is of mutual benefit: produces rice + healthy source of protein for farmer

Question 17

Name 5 negative impacts of fish farms

Answer 17

• loss of habitats
• pollution (w feed, antibiotics etc…)
• spread of disease
• escaped species inc.GMO that interbreed w wild fish
• escaped species may outcompete native species + cause population to crash

Question 18

Atlantic salmon + fish farming

Answer 18

• Wild Atlantic salmon live in North Atlantic + Baltic seas
• Due to overfishing, commercial market for wild salmon crashed
• Now farmed in fish farms
• Although commercial successful, farms create pollution as fish are kept in high densities + their faeces and chemicals enter ocean
• Sea lice are a common problem
• If farmed salmon escape + interbreed, reduces genetic fitness of wild stock so their ability to survive in wild is reduced

Question 19

4 ways technology has developed to be more efficient at catching fish on large scale

Answer 19

> latest satellite technology +GPS navigation
fishing fleets larger w blast freezing so can stay out at sea for weeks
indiscriminate fishing gear will take all organisms in area, even if not target species
trawlers drag huge nets over seabed virtually clearcutting it

Question 20

Example of nations fighting over fish

Answer 20

1970s: Iceland banned all foreign vessels from fishing in Icelandic waters. This led to 3 ‘cod wars’ between Britain + Iceland

Question 21

The world fish catch is just over 90million tonnes per year. How much is ‘by-catch’?

Answer 21

20million tonnes are by-catch - unwanted fish and other marine animals that are thrown back into the oceans from the fishing boats. Most are dead or dying.

Question 22

How can the deterioration of oceanic fisheries be reversed? // granting fishers ownership stakes in fish stocks

Answer 22

• Granting fishers an ownership stake in fish stocks
• e.g. fishers in Iceland + NewZ have used marketable quotas, allowing them to sell catch rights, since late 1980s.
• The upshot is smaller but more profitable catches
• ‘Tragedy of the Commons’ problem is averted

Question 23

How can the deterioration of oceanic fisheries be reversed? // marine reserves

Answer 23

• studies have shown well-postitioned + fully protected marine reserves can help replenish an overfished area
• by giving fish a refuge to breed + mature in, reserves can increase the size + total no. of fish both in reserve + surrounding waters

e.g a network of reserves established off St Lucia in 1995 has raised the catch of adjacent small-scale fishers by 90%

Question 24

How can the deterioration of oceanic fisheries be reversed? // consumer

Answer 24

Consumers can promote healthy fishery production by eating less fish + buying seafood from well managed, abundantly stocked fisheries

Question 25

Why are fish stocks shrinking?

Answer 25

> Industrialised nations subsidise their fleets by $50 billion a year
demand outstrips supply

Question 26

The tragedy of the commons in fishing and how we can overcome it

Answer 26

• Tensions between common good + needs of individual
• If resource seen as belonging to all, we tend to exploit it for our short-term gain
• If we don’t take it, somebody else will
• Solution is often regulation + legislation by authorities which limits the amount available to any individual

Question 27

What is the United Nations Convention on the Laws of the Sea?

Answer 27

• international agreement written over decades
• attempts to define the rights + responsibilities of nations w respect to seas + marine resources
• most countries have signed the convention

Question 28

What is a sustainable yield?

Answer 28

The increase in natural income that can be exploited each year without depleting the original stock or its potential for replenishment

Question 29

What is maximum sustainable yield?

Answer 29

The highest amount that can be taken w/o permanently depleting the stock

Question 30

The carrying capacity for each species depends on…

Answer 30

• its reproductive strategy
• its longevity
• the indigenous resources of habitat / ecosystem

Question 31

How is the sustainable yield calculated?

Answer 31

SY = annual growth + recruitment - annual death + emigration

Question 32

In practise, harvesting the maximum sustainable yield normally leads to population decline and an unsustainable fishery. Why is this?

Answer 32

• population dynamics of target species normally predicted rather than the species numbers being quantitively measures
• hard to be precise about pop. size
• estimates made on previous experience
• disease may strike population
• model doesn’t look at age + sex ratio // harvesting young fish or reproductive females has much worse impact

Question 33

What is a much safer approach compared to MSY?

Answer 33

• the harvesting of an Optimum Sustainable Yield
• requires less effort than MSY
• maximises difference between total revenue + total cost
• has much greater safety margin than MSY
• but still may impact pop size if there are other environmental pressures