1. What factors affect the supply and use of fish?
Learning outcomes:
To describe and explain the main physical factors that affect fish stocks.
To understand how technological changes and government policies have led to overfishing.

2. Starter - finish the sentence
Fishing is …
Fishing is the collection of a wide range of species including fish and shellfish.
Fishing is the last large- scale human hunting activity.
Fishing provides an important source of protein. Especially in LEDCs.
Reading notes can be viewed online
Reading - World Fisheries Factfile and World Fish Production, 2004

3. OUTCOME 1 - What physical factors affect the supply and use of fish?
The two most important factors that affect marine productivity are light and nutrients.
WHY?
Discuss in pairs why each of the following factors might affect availability of light and nutrients.
Depth of water
Latitude
Turbidity (cloudiness of the water)
Proximity to the coast
Hand out showing map and nutrient movements in the sea from page 259 in the Env studies text book.
Look at the map showing the productivity of different ocean areas. Write down 3 facts about it.

4. OUTCOME 1 - What physical factors affect the supply and use of fish?
Explanation
Depth of water
Light essential for photosynthesis cannot penetrate deep water. The depth that light can penetrate is called the photic zone. Kelp or algae that anchor to the sea bed are only found in shallow water.
Latitude
The tilted axis of the earth produces seasonal variations in sunlight intensity and day length. In polar regions these variations are extreme resulting in algal blooms that support rich food webs
Turbidity
Where fine sediments are washed in by rivers or where stormy weather disturbs sediments turbidity is increased. This affects light penetration and photosynthesis.
Proximity to the coast
Productivity is maintained where fresh nutrients are continually arriving such as in a coastal area where rivers bring nutrients from the soil it’s catchment area. These rarely get carried out to open ocean so productivity out at sea is often low unless there is an upwelling.
Taken from 258 in ES text book

5. The Tragedy of the Commons
OUTCOME 2 - To understand how technological changes and governments have led to overfishing
The Tragedy of the Commons
Marine fishing is a classic example of the tragedy of the commons.
No one owns the fish in the sea until they are caught, but all those who fish affect one another.
As long as individuals and groups benefit from using a resource, exploitation will continue even when then resource begins to degrade.
Key Principle = although selfish behaviour may not be in an individual’s long term interest, neither is it in an individual’s interest to be unselfish unless everyone is.
Litter in school analogy or strawberries!
This has resulted in overfishing which is when fish are harvested faster than they can breed to replace themselves.

6. Technological Advances which have improved the efficiency of fishing
OUTCOME 2 - To understand how technological changes and governments have led to overfishing
Technological Advances which have improved the efficiency of fishing
LORAN = Long range navigation
Teacher info on techniques = page 151 Red book
Hi-tech fishing vessels ‘the strip miners of the sea’
LORAN (Long range navigation) and GPS
Fishing techniques such as trawling, dredging, purse seine and surround nets

7. OUTCOME 2 - To understand how technological changes and governments have led to overfishing
Bottom otter trawls
Surrounding net
Used for pelagic species e.g. tuna surround fish from the sides and from underneath, thus preventing fish from escaping by diving downwards.
Cone-shaped net kept open by otter boards which is dragged across the ocean floor
Seine
Dredge
A very long net, with or without a bag in the centre. Operated with 2 long ropes fixed to its ends for hauling and herding demersal fish
Heavy, metal structures, sometimes with teeth to scrape along or cut through the bottom in order to catch mussels, scallops, oysters etc

8. Are Governments to blame?
OUTCOME 2 - To understand how technological changes and governments have led to overfishing
Are Governments to blame?
This can be printed for students