4.3 Aquatic Food Production Systems Flashcards
What is the role of phytoplankton in marine food chains?
They are primary producers and perform photosynthesis
Phytoplankton produce food for themselves and oxygen for animals.
How many fishers are directly engaged in fishing and fish farming worldwide?
Nearly 35 million
Most fishers are concentrated in developing countries.
What are the principal ethical issues in fisheries?
Poverty, the right to food, legislation, overfishing, ecosystem degradation
These issues relate to human and ecosystem well-being.
What impact does overfishing have on fish stocks?
It makes recovery very difficult
Once a fish stock collapses, it struggles to return to sustainable levels.
What is aquaculture?
raising fish comercially, usually for food.
What are some major environmental impacts of aquaculture?
- loss of natural habitat = human activies interfere with natural process (migration, predator-prey relationships, etc.)
- many fish in aquaculture (ie. salmon) need to be fed other fish for food -> ‘using’/’growing’ more fish than consumed
- disease spreading from farmed fish -> wild stocks
- pollution (uneaten food, feaces, chemicals) contaminating surrounding waters
- accidental escape of genetically modified fish -> can affect local, wild fish populations / gene pools when they interbreed
-> decrease of wild fish genetic diversity
-> potential introduction of non-natural genetic variation
What is the whaling controversy about?
The debate over whale hunting focusing on sustainability and conservation
It also includes issues of ownership and national sovereignty.
True or False: Aquaculture is the fastest growing form of food production in the world.
True
Due to the peak of wild fisheries.
What is a significant social impact of aquaculture?
Traditional livelihood and community displacement
Conflicts arise from export-driven commodity production.
What social issue is associated with the establishment of shrimp farms in developing countries?
Large scale displacement of families
This contributes to landlessness and food insecurity.
sustainable yield definition
the rate of increase in naural capital that can be exploited without depleting the original stock or its potential for replenishment
2 types of ‘fishery’
capture (harvesting seafood from wild stocks) and aquaculture (intervention in the rearing process, to enhance production)
bottom trawling
- weighted net that drags across sea floor
longlining
- 50 miles of baited hooks
sustainable aquaculture case study
offshore shellfish, Devon UK
- mussels on long lines underwater
- custom made rope: high surface area, easier to attach
- put bycatch back in water (no nets are used so bycatch isnt dead)
- few inputs
- 56 different species feed on/by ropes -> inreased biodiversity -> more species in seabed
- shells made up of carbon -> carbon sink (in creation, take carbon out of atmosphere)
sustainability
social:
- protein in mussels
- low calories
- rich in nutrients and minerals
- alternative to meat
economic:
- expanding company
- provides jobs
unsustainable aquaculture case study
shrimp farming, Thailand
industry expanded in 1980s/1990s due to high global demand
how does the shrimp farming in Thailand impact inputs into the system?
- large amounts of feed needed
-> sourced through wildcaught fish - this reduces oceanic fish stocks
- disease outbreaks require large amounts of antibiotics/chemicals
-> can create antibiotic resistant bacteria
shrimp farming in Thailand/fish density in cages
- shrimp stocked at high densities = stress, disease, mortality
-> increases risk of disease spread - more resource managemet needed
shrimp farming in Thailand/water pollution
- open aquaculture = high amounts of organic waste, nutrients, chemicals, antibiotics into surrounding waters
-> eutrophication = oxygen depletion = anoxic waters (death of surrounding marine life)
shrimp farming in Thailand/habitat loss
- Mangrove forests are often cleared to construct shrimp ponds -> necessary for wildlife + essential buffers against coastal erosion/flooding/storm surges
about 50-60% of Thailands forests clared over the last few decades
shrimp farming in Thailand/interference with local processes
- less mangroves = disrupted coastal sedimentation, erosion control
-> altered water flow + sedimentation patterns = negative impact on local biodiversity
shrimp farming in Thailand/invasive species (incl. GM species)
- non native shrimp occasionally escape
-> compete with natives species for food and habitat
-> alters local biodiversity + niches of local species
open aquaculture systems characteristics
- open air
- in pre-existing body of water eg. sea or lake
- little control over enviornmental conditions
- some contact with other species in the enviornment
semi-closed aquaculture systems characteristics
- often inside a building
- body of water is often man made
- some (or much) control over enviornmental conditions
- little contact with other species in the enviornment
Notes on energy efficiency aquatic vs terrerstiral food chains
- in aquatic systems, most food is harvested from top trophic levels (less energy efficient than terrestrial systems)
- initial fixing of available sunlight energy is less efficient due to the absorption and reflection of light on water
- energy conversions along aquatic food chains are more efficient:
-> endothermic (lose less to keep bodies warm)
-> shorter food chains
how does MSY provide indefinite stable growth?
aims to maintain pop. size at maximum growth rate by harvesting individuals that would normally be added to the population = indefinite growth
modern tool to solve some issues of global overfishing
sonar -> distinguishes fish that is watned = decreases bycatch
managing fish stocks: quotas
fish biologists estimate MSY based on current stock levels / rates of replenishment -> politicians agree on Total Allowable Catches -> shared & lead to invidual limits (quotas)
CRITICISM:
by-catch is often thrown back into the sea to maintain allowable size limits
managing fish stocks: reduction in fishing effort
- reducing # of boats fishing
- restricting boat size
- restricting fishing times
- restricing type of gear used (inclu. limits of net size, mesh size (larger nets reduces number of juvenlie/baby fish caught))
why is harvesting some species (such as seals, sharks and whales) controversial?
- ethical issues -> biorights - rights of an endangered species, a unique species, or landscape to be ‘left alone’
- rights of indigenous culture + international legislation conservation needs to be considered
IWC
international whaling commission
- decides hunting quotas -> based on stats of its scientific committee
- 1982 -> voted to establish a ban on commerical whaling (took effect in 1986)
Inuit whaling
- IWC allows Inuits in Alaska to kill certian quota of Bowhead Whales
-> half of meat in Inuit diet
-> Bowhead whales not endangered
-> hunt is sustianable
CONSERVATIONISTS believe…
- whales have biorights
- shouldnt be killed
Japanese whaling
- Japan reluctantly stopped whaling in 1986 -> continued for “scientific purposes” to establish size/dynamics of whale populations in Antarctic
- Australia + other Western countries oppossed on conservation grounds
- Australia took case to ICJ court = Japans “scientific research” masks commerical whaling
- Japan said it was an attempt to impose its cultural norms and that Mink Whales / other species were plentiful, whaling activities were sustainable
- 2014: ICJ ruled Japan needs to halt whaling because their scientific output was limited
General threats to whales through whaling
- collision with ships
- chemical pollution
- habitat degradation
- noise pollution
- by-catch (unintentional capture of whales in fish nets)
What large project has helped in protecting whales?
(1994) Southern Ocean around Antarctia = whale sanctuary
