Oceans and Fisheries Flashcards
Uses of water (resource potential)
- Food
- Tourism
- Building materials
- Source of drinking water
- Transportation
- Power generation
Define aquaculture
The rearing of aquatic animals and cultivation of aquatic plants for food
Examples of building materials formed through erosional processes of the coast and on land
- Gold
- Sand
- Gravel
- Limestone
Methods of harnessing the power of the oceans
- Onshore wave generators
- Offshore wave generators
- Tidal barrages
- Tidal stream generators
Give an example of how water is used in tourism, transportation and as drinking water
Tourism- beaches, but unsustainable tourism may lead to habitat destruction
Transporation- bulk carriers, container ships, for trade
Drinking water- using desalination plants
Ocean current? Factors that influence them?
An ocean current is a continuous movement of seawater set in a direction that is driven by-
- The gravitational pull of the moon
- Wind
- Thermohaline circulation
- Tides
- Rotation of the Earth
Define thermohaline circulation
The oceanic circulation system driven by the differences in temperature and salinity
Explain the distribution of ocean currents
The warm surface water moves away from the equator in giant spiral motions.
Define gyres
A circular system of ocean currents that spin anticlockwise in the southern hemisphere and clockwise in the northern
Define coriolis effect
The effect the rotation of the Earth has
Explain the massive global conveyer belt
Since oceans do not have a uniform salinity or temperature, the warm water reaches the polar region and cools down, becoming saltier and denser leading it to sink down and travel back towards the equator. This nutrient-rich water comes to the surface through upwelling, which attracts fish stimulating the food chain
What are some key characteristics of areas where major fish populations can be found
- In shallow waters around the continental shelf with sunlight
- Around islands
- Where ocean currents cause upwelling
- In coastal waters
- Near coral reefs
What 3 elements make a key factor in the distribution
The relationship between topography, ocean currents and photosynthesis
Explain the El Niño effect
This climate cycle occurs every 2-7 years in the Pacific Ocean. These lead to weakened winds and reversed warm ocean current patterns, with drier conditions in Asia and wetter in South America.
In a normal year, warm water currents move toward the left which leads to rainy weather in Australia. This leaves cold water on the right in Peru causing high levels of upwelling and fish populations there.
However, in an ENSO year, the warm water moves back eastwards towards Peru leading to the cold Humboldt (Peruvian) current feeling overwhelmed with the heat, making it a warmer winter and heavy rainfall but no upwelling of cold water which reduces fish concentrations.
Define bycatch
The unwanted fish species and marine animals caught in fishing nets when fishing for a different species
Normally because they’re of the wrong sex, size, or species.
A lot of the time the species caught are too small and therefore discarded back dead which affects the future fish population.
Define overfishing
When more fish are caught than the population can replace through natural reproduction
What leads to overfishing?
- Lack of management
- Increasing technology
- Usage of large ships that companies can afford due to the increase of fish demand
- Radar and spotter helicopters
- High demand for fish
Explain what a fish factory trawler is
These are massive ships that pump vasts amount of catches from super trawlers etc, load them onto the ship, and freeze them on board, ready to be shipped off. (The dead bycatch is thrown back in the sea)
What threatens fish species?
- Overfishing
- Catching of vulnerable species
- Destructive fishing methods
- Illegal or pirate fishing
Aquaculture and fish farming
Raising fish in tanks and enclosures- allows species to recover
However, this can lead to water pollution and even disease transfer, plus fish are provided as food for other fish sometimes
How can you manage the decreasing fish populations?
- Switch from diamond to square fish nets (smaller fish can escape)
- Pole and line fishing- inconvenient, but reduces bycatch as its selective
- Quotas- reduce the number of fish caught and ban catching of endangered species
- Closed seasons- breeding season
- Protected reserves- Marine Protected Areas (MPA)
- Conservation Laws
- International agreements- banning international fishers
Why are quotas a controversial way of management?
+
Allows fish populations to recover as there are set limits on the amount one can catch
Bans endangered species preventing extinction
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Fishermen have to discard perfectly fine dead fish just so they don’t get fined
Fishing vessels may reach the quota limit by catching the wrong fish- discard
Explain why the largest fish populations are found in shallow waters where there is upwelling
Phytoplanktons make food using sunlight which can’t penetrate very deep into the water. However, the other resources necessary are not found at surface level. Therefore, upwelling brings those minerals etc to the surface which allows fish to survive in the shallow waters.
Name 2 cold currents + 2 warm currents
Cold- Peruvian (Humboldt) current, Labrador current
Warm- South equatorial current, Brazil current
Why are you likely to find fish near the continental shelves?
High oxygen concentration: respiration
High light penetration: photosynthesis
Abundance of CO2: photosynthesis
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