Aquatic food production systems Flashcards
Why do marine ecosystems have high stability and resistance?
Marine ecosystems are usually very biodiverse and so have high stability and resilience
What is the continental shelf?
An extension of continents under the ocean. Where continental shelf exists it creates shallow water
Why is the continental shelf important?
- 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
What are phytoplankton and why are they so important? What about zooplankton?
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
Marine ecosystems can be classified as:
BENTHIC // living on or in the sea bed
PELAGIC // living surrounded by water from above the sea bed to the surface
What is a fishery?
A fishery exists when fish are harvested in some way. It includes capture of wild fish and aquaculture (fish farming)
What percentage of fishery activity is in oceans?
90%
How many people make a livelihood in fisheries?
Up to half a billion people
How many people gain 20% of their protein intake from fish
3 billion
Health benefits of fish
- high in protein
- low in sat. fat
- contain vitamins A,B,D needed for healthy diet
What percentage of the world’s fisheries are fully exploited, seriously depleted or too low to allow recovery?
70%
What is aquaculture?
The farming of aquatic organisms in both coastal and inland areas involving interventions in the rearing process to enhance production
On average, how much fish and meat does a person eat per year?
- 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
Why does most of the extra fish come from fish farms?
- 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
Name 3 ways fish farming is becoming more sustainable
> 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
What percentage of all farmed fish is produced by China and why is this so important for Chinese farmers?
- 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
Name 5 negative impacts of fish farms
- 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
Atlantic salmon + fish farming
- 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
4 ways technology has developed to be more efficient at catching fish on large scale
> 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
Example of nations fighting over fish
1970s: Iceland banned all foreign vessels from fishing in Icelandic waters. This led to 3 ‘cod wars’ between Britain + Iceland
The world fish catch is just over 90million tonnes per year. How much is ‘by-catch’?
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.
How can the deterioration of oceanic fisheries be reversed? // granting fishers ownership stakes in fish stocks
- 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
How can the deterioration of oceanic fisheries be reversed? // marine reserves
- 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%
How can the deterioration of oceanic fisheries be reversed? // consumer
Consumers can promote healthy fishery production by eating less fish + buying seafood from well managed, abundantly stocked fisheries
