Chapter 5: Oceans and Fisheries Flashcards
Elaborate on the resource potential of oceans
FOOD - fish - world fishery yields from sea are 80 million tonnes/year - main fisheries on continental shelves - water there is shallow - light easily penetrates+more oxygen - nutrients abundant on shelf from land
CHEMICALS+MATERIALS - have compounds containing more than 60 chemical elements - materials can be eroded from land to sea - can be extracted directly= salt, magnesium, gold, tin, titanium, diamonds - ocean floor mined for substances (diamonds) - mining needs to be done carefully - can cause damage to habitats nad produce dust particles
WAVE - eg - Islay LIMPET in Scotland - Agucadoura Wave Farm in Portugal
TIDAL - SIhwa Lake tidal power station - penzhin tidal power plant project
TOURISM - natural sites - diving - fishing - beach - ecotourism - whale watching
TRANSPORT - ships - cargo ships -
DRINKING WATER - desalination
Describe three types of merchant ships
BULK CARRIERS - transport foods such as rice and wheat
TANKERS - transport of fluids - oil and petroleum - lpg and lng - vegetable oils - wine
CRUISE SHIPS - for pleasure voyages
OCEAN LINER - to transport people from port to port
CONTAINER SHIPS - containerisation - load carries in lorry sized containers
REFRIFERATED SHIPS - food, dairy, fish
FERRIES - b/w islands or mainland - For people
COASTAL TRADING VESSELS - island close together
ROLL ON/OFF SHIPS - vehicles and loads can be driven in and off
prevailing wind
the direction from which the wind nearly always blows in a prticular area
Why are there some continental shelf areas that do not have fisheries
- lack of ecnomic resources
- Phytoplankton need minerals to make proteins along with the requirements for photosynthesis
- making proteins requires nitrogen and sulfur - necleic acids which form the genes of living things also require phosphorous
- chlorophyll needs magnesium
- lack of minerals reduces fish hence no fisheries
- usually minerals found due to upwelling and surface currents - current system or decay
Describe the patterns of major ocean currents
- surface currents are caused by prevailing winds - however final direction depends on the shape of the land around any point
- currents in Southern Hemisphere are generally anticlockwise as winds blow from south east and force the western Australian, Benguela, and Peruvian currents nothwards
- cold currents come from North or South pole
- warm currents come from the tropics of flow along either side of the equator
pg 117
Over fishing
when the number of fish that is caught is greater than the rate at which the fish reproduce - leading to a fall in the number of fish in the area
What is upwelling
areas where minerals at the ocean floor are brought ot the surface by currents
What is the euphotic zone and how is it important
- euphotic zone is the top 200m or so of seawater through which light can penetrate and in which photosynthesis happens
- Fish cannot make own food
- herbivores eat phytoplankton
- carnivores eat other fish
- phytoplankton need to photosynthesise - need light, water, CO2 - light is the limiting factor - ocean can only properly absorb in euphotic zone - hence fish found in shallower water - continental shelves
What is ENSO?
- El Nino Southern Oscillation
- every 10-15 years
- not understood why this takes place
- change in the normal trade winds
- leads to warm, nutrient poor water coming into the region from equator
- stops the upwelling of cold, nutrient rich water
- reduces photosythesis changes system of world fisheries
- change in pattern of current in the oceans of the south pacific
pg 119 for eg
What are the symptoms of overfishing?
- reduced catch
- size of the fish caught gets progressively smaller
Why has sustainable fishing been difficult to practice over the years
- usually the main reason for fishing is economic gain - meaning the number of fish caught are those that are available
- this leads to over fishing and bycatch
- usually laws created are not implemented
pg 121 for eg
What is bycatch?
- animals caught by fisheries that are not the intended target of their fishing effort
- wrong species
- wrong sex
- individuals that are too small
- for eg worldwide shrimp fisheries only account for 2% or the world’s catch but 30% of the world’s bycatch
- tun fisheries have dolphin bycatch
What are the major reasons of overfishing?
- economic reasons - increasing demand for food and fish
- technology and imporved fishing methods > bigger boats that can stay a long way from port for many weeks + you can use SONAR detection and detaield weather detection > they fish more than needed
- usage of huge nets > scoop up everythingin area > almost half of what is caught in nets like these are regularly discarded as bycatch
Give some examples of huge nets used around the world to catch fish
**Trawl nets + bottom trawl nets **- catch all kinds of unwanted species + damage seabed
Drift Nets - drift with current and are not anchored - used in coastal waters
Seine Net + purse seine - hang likr a curtain in hte water - surrounding net
Dredge Nets - dragged along seabeds - mainly to catch shellfish + other creatures living in mud - dig up with teeth or water jets
pg 122 for picture reference
What is aquaculture
- farming freshwater fish
- Cobia is the best example of successful aquaculture
