4.3 Flashcards
Why are marine ecosystems like coral reefs and mangroves considered highly stable and resilient?
Because they are highly biodiverse.
Where does half of marine productivity occur?
In coastal regions above the continental shelf.
Why do deep ocean regions have low productivity?
Because there is no light, so primary production relies on chemotrophs and dead organic matter.
What is the continental shelf?
The extension of continents under the sea, creating shallow waters with high
productivity
Why is the continental shelf important?
It allows photosynthesis, nutrient upwelling, and is part of a country’s exclusive economic zone (EEZ)
What are phytoplankton?
Photosynthetic, single-celled producers responsible for 99% of oceanic primary
productivity
What are zooplankton?
Single-celled animals that eat phytoplankton and support marine food webs.
What are benthic organisms?
Organisms that live on or in the seabed.
What are pelagic organisms?
Organisms that live in open water, not near the bottom.
Name 6 reasons for increased demand for aquatic food resources
GCNUGA
- a growing human population
- changing dietary patterns (economic growth -> increased consumption of protein rich foods)
- nutritional benefits of seafood (recognised as a valuable source for essential neutropenia such as omega-3 fatty acids, vitamins and minerals)
- urbanization and the rising middle class (increased demand for diverse and higher value food options)
- global trade and supply chains (advances in transportation and the expansion of global trade networks have made it easier to important and export seafood products -> increased availability of seafood to communities)
- aquaculture production
What is aquaculture?
Farming aquatic organisms in controlled environments.
What is bottom trawling & its impacts?
involves dragging heavy nets along the seabed.
impacts:
- destroys habits such as coral reefs
- results in significant bycatch (catching non-target species)
- disturbs sediment, causing sediment illusion and releasing other trapped pollutants
What is ghost fishing & its impacts?
occurs when abandoned or lost fishing gear continues to catch marine life (eg. ghost nets)
impacts:
- leads to unnecessary deaths
- causes entanglement of marine organisms, including endangered species
- contributes to marine debris and pollution
use of poison in fishing & its impacts?
some fishermen use poisons and toxic substances, such as cyanide, to stun or kill fish, making them easier to catch
impacts:
- kill/damage a wide range of marine life
- cyanide kills coral polyps and other organisms that form the coral reef structure, leading to reef degradation and overall loss of biodiversity
- highly unsustainable and illegal in many places
use of explosives in fishing & its impacts?
some fishermen use explosives, such as dynamite, to stun, or kill fish, making them easier to catch
impacts:
- destroy marine habitats and kill indiscriminately (kill non-target species)
- causes extensive damage to coral reefs and other important marine habitats
- highly unsustainable and illegal in many places
What is overfishing?
Harvesting fish faster than they can reproduce
What is maximum sustainable yield (MSY)?
Highest possible annual catch that can be sustained over time without depleting the fish stock
Impact of fishing farms include:
- Loss of habitats
- Pollution (with feed, antifouling agents, antibiotics and other medicines added to the fish pens)
- Spread of diseases
- Escaped species including GMO’s which may survive to interbreed with wild fish
- Escaped species may also outcompete native species and cause the population to crash
Reasons why humans have gotten good at finding and catching fish on an industrial scale:
Commercial fishing informed by the latest satellite technology, GPS navigation and fish finding scanning technology of military quality
Fishing fleets have become larger, and with modern refrigeration techniques, including blast freezing, they can stay at sea for weeks or an entire season
Indiscriminate fishing gear will take all organisms in the area, regardless of whether they are the target species or not
Trawlers drag huge nets over the seabed virtually clearcutting it
What is the tragedy of the commons?
a metaphor illustrating the tension between the common good and the needs of the individual and how they can be in conflict.
assumption that in the short term it is worth taking all the fish you can because, if you do not, someone else will. assumes that humans are selfish and not altruistic.
eg. of tragedy of the commons?
exploitation of the oceans ->
the grand banks off the coast of Newfoundland (once the richest fishing grounds on earth).
However, in the 1990’s fishing stocks crashed and by 1995, cod and flounder fishing there had been closed in an attempt to conserve remaining stocks.
So far there has been little, if any, recovery of fish numbers.
solution to the tragedy of the commons?
regulation and legislation by authorities which limits the amount of common goods available to any individual.
Increasing the size of gaps in fishing nets can help in two main ways:
* fewer unwanted species (that are often discarded) will be caught and killed. since they can escape through larger net gaps (as long as they are smaller than the species being caught)
* juvenile fish of the fish species being caught can escape through larger net gaps (this means they can reach breeding age and have offspring before they are caught and killed. this ensures the population of the fish species being caught can be replenished.)
What are fishing quotas?
fishing quotas limit the number and size of particular fish species that can be caught in a given area.
