12: Aquaculture Flashcards
What factors limit ocean productivity?
- light intensity
- nutrient availability (phosphates and nitrates)
- oxygen concentration
How does upwelling aid productivity?
Upwelling brings up nutrients when the wind pushes the surface water away and cold water is drawn up from the bottom.
Why are open oceans less productive than coastlines?
Open water in much deeper, so nutrients sink to the bottom, where there is very little light.
Coastlines are more shallow so the nutrients stays where there’s still light and gets moved about by storms and waves. They also get run off from land
What are the names for the fishing of different depths?
Pelagic: catching fish that live in shoals shallow to medium deep
demersal: catching fish that swim in mixed shoals at the sea floor
Benthic: fish that live inside the sediment such as shell fish
What examples of pelagic fishing are there
- long line
- purse seine
- otter trawl
- drift net
What examples of demersal are there?
- beam trawl
- lobster pot
- otter tawl
What examples of benthic fishing are there?
scallop dredge
What methods are there to reduce over fishing?
- closed seasons
- reducing netsize/hole size
- limit number of boats/days at sea
- limit size of boat
- ban on fishing certain well breeding individuals (lobster)
- no take zones
- population seeding
- quotas
- marine stewardship council
- dolphin pingers and bycatch removal devices in nets
- longlining reduces by catch
What methods are there to reduce waste in aquaculture?
- polyculture so that a variety of fish consume all the different food sources and prevent over population of each other
- integrated multi-trophic aquaculture to minimise waste
- aquaponics so that excess nutrients is used in hydroponics of plants
- use fish lower down the food chain such as herbivors so less energy used
How does aquaculture maximise yield name 10? (12)
1) currents to allow high pop. density
2) tempertuare and light control (can prevent breeding 3) seasons where there is little growth)
4) eggs kept in optimum conditions
5) water circulates from young to old to avoid spread of disease
6) gender control using hormones
7) selective breeding
8) high oxygen levels
9) control of predation
10) antibiotics in feed
11) adding fish such as rass which eat pests like sea lice or use of pesticides
12) adding high amounts of food
What are the negative environmental effects of aquaculture on the environment?
-use of pesticides killing non-target species
-antibiotic resistance
-escaped fish breeding with wild population
(genetic contamination, compettion with wild, invasive species, spread disease)
-excess food and waste can cause eutrophication
How can the environmental impacts of aquaculture be reduced?
Food supply
Overfishing to make food pellets
- Culture herbivorous fish instead
- use more plant products in pellets
How can the environmental impacts of aquaculture be reduced?
Pesticide pollution
May kill non-target species
- cleaning of cages
- biological control of pests (russ eating sea lice)
How can the environmental impacts of aquaculture be reduced?
Antibiotic resistance
-lower stocking densities
How can the environmental impacts of aquaculture be reduced?
Escaping fish
Better nets
