4.3 aquatic food production systems Flashcards
(37 cards)
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
