4.3 aquatic food production systems Flashcards
marine ecosystems
- oceans
- estuaries
- mangroves
- coral reefs
- salt-marshes
- 70% of earths surface
marine trophic levels
primary producers
- base of the food web
- microscopic phytoplankton, seaweed
marine trophic levels
primary consumers
- zooplankton
- small floating animals that graze on phytoplankton
marine trophic levels
secondary consumers
- small predators, some fish
marine trophic levels
tertiary consumers
- top predators, large fish
- marine mammals
coastal waters and shallow seas tend to be more productive because
- nutrients that precipitate out a resuspended by wind and currents in shallow water
- river input brings in more nutrients
- sunlight can penetrate down to the sea floor, driving photosynthesis
freshwater trophic levels
primary producers
- phytoplankton
freshwater trophic levels
primary consumers
- zooplankton
freshwater trophic levels
secondary consumers
- fish
- birds
- ducks
- drogs
freshwater trophic levels
tertiary consumers
- large fish and birds
- mammals
factors contributing to the increasing demand for fish
- human population growth
- promotion of health benefits consuming fish, protein, nutrients, essential fatty acids
- better standards of living
- imports
seal hunting
- traditional cultures, only 3% of total seals hunted globally each year
controversial
- concerns over species becoming threatened
- inhumane methods of killing
- most meat wasted
- incorrectly blamed for the collapse of newfoundland cod
- ice melting threatening seals habitat
government
- quotas
- open and close hunting season
- limited boats and catches per day
- banning babies and certain species
- not enforces well
energy efficiency of aquatic food systems
- less efficient than terrestrial food systems
- less light, absorbed or reflected by water
- humans eat high up the food chain, greater energy loss
growth in capture fisheries
- population, popularity
- more fishing fleets
- able to fish further from the shore and stay out longer
- sonar, radar, satelite technology
- process, preserve and freeze out at sea
- changing fishing gear
use of nets
trawler nets
- dragging funnel shaped net across the seabed
- damages seabed
use of nets
drift nets
- hung vertically in water
- bycatch, turtles, sharks, dolphins
- banned in many places
marine capture fisheries not continuing to expand?
- consequence of overfishing and habitat degradation
maximum sustainable yield (MSY)
- max harvest that can be obtained annually without impacting the standing stock and it’s ability to replenish itself
- hard to calculate, can still lead to over-exploitation
reasons for overfishing
property rights
- nobody owns the fish, swim through large areas across national boundaries
- don’t want to spend money conserving for other countries to harvest
reasons for overfishing
zero sum game
- need to convince people to sacrifice short term gain to benefit the future
- fish less, others fish more, conservation loose out
managing fish stocks
use of quotas
- estimate MSY, politicians set total allowable catches (TACs)
- bycatch discarded as waste, penalties
managing fish stocks
reduction in fishing effort
- reducing number of boats, boat size, fishing gear used, limits on minimum fish size, fishing times
managing fish stocks
use of exclusion zones and marine protected areas
- fishing banned in certain areas
- legislation enforced
newfoundland cod fishing case study
- tragedy of commons
- largest cod stocks
- 1950s technology development
- 1990s, loss of fish stocks, still low numbers 30 years later
- unemployment
iceland cod case study
- slight decline, government took action to prevent similar to newfoundland
- protecting territorial waters
- restrictions on fishing gear and fleet sizes
- strict quotas
- banning disposal of bycatch
- diversification of target species
- use of exclusion zones
- high level of enforcement
aquaculture
open based system
- most popular
- farming within a natural aquatic ecosystem, sea, lake
- little control over environmental factors
aquaculture
semi closed system
- abstraction of water from sea or lakes to use within tanks or ponds on land
- greater control over environmental conditions
- more expensive
environmental impacts of aquaculture
increase in organic sediments
- waste, uneaten fish food, feces, medicines
- precipitates to below the cage and can accumulate
- can cause anoxic conditions, reducing biodiversity
- movement, sufficient aeration of water
environmental impacts of aquaculture
increase in available nutrients
- soluble nutrients released from uneaten fish food and feces, increase dissolved nutrient levels in the water
- increase primary production, algal bloom, harm fish
environmental impacts of aquaculture
use of medicines and hormones
- contaminate the water and impact other aquatic life
environmental impacts of aquaculture
use of antifouling agents
- used to prevent growth of algae and other organisms on the cage
- toxic to mollusks, decrease biodiversity
environmental impacts of aquaculture
spread of disease
- heavily stocked, disease spreads from one fish to another
- potentially outside of cages
environmental impacts of aquaculture
escaped fish
- threaten wild stocks, competing, transmit disease
- may have advantage for survival over wildfish, decrease biodiversity
environmental impacts of aquaculture
attracted predators
- predators can become caught in the net
-underwater acoustics to deter predators
managing environmental impacts of aquaculture
- reducing waste of uneaten food, not overfeeding
- effective application of medicine
- regular removal of dead fish
- moving the cages to prevent build up of organic sediments
- sufficient movement and water exchange, disperse blooms, waste/nutrient build up
- aerate the water
environmental impacts of aquaculture
loss of habitats
- clear land for aquaculture
- mangrove forests, reduce natural storm protection
- space taken up other animals can’t use
thailand shrimp aquaculture case study
- 2/3 mangrove forests destroyed
- all problems with aquaculture happening
- international pressure to reduce environmental degradation
- legislation, better controls
