Download Aquatic Food Production systems 1. Fishing

Aquatic Food Production systems
1.Fishing. Factors that affect productivity
Key Questions.
1. What are the
factors controlling
marine
productivity?
2. Why is there a
difference in
productivity
between open
ocean and the
continental shelf?
Instructions
• Please complete the tasks on this powerpoint.
• The choice of format is yours. It can be
handwritten or typed in word.
• You will need pages 258 to 262 in the textbook.
• I have also uploaded a factsheet ‘Ocean
Productivity’
• This is 3 lessons worth of work. I hope to see you
on Friday 23rd for lessons as normal when we will
check through these tasks!
TASK 1 list 3 differences between
agriculture and fishing.
Task 2 Complete a glossary of the following key terms. You will
need the text book, the factsheet and perhaps notes from
your other units.
1. Biomass
2. Net Primary Productivity
3. Algae
4. Phytoplankton
5. algal blooms
6. Photic layer
7. Upwelling
8. Ocean salinity
9. Ocean density
10. Ocean thermocline
What are the factors controlling marine productivity?
TASK Use pages 258 and 9 to answer the following questions
Light
1. Why are kelp, algae and seaweed only found in
shallow water?
2. How does photosynthesis take place in deeper
water?
3. Where and why might light penetration be
reduced?
4. How does latitude affect light and marine
productivity in oceans?
5. Why are highest rates of NPP at a depth of 2030 metres? (Fact Sheet)
What are the factors controlling marine productivity?
TASK Use pages 258 and 9 to answer the following questions
Nutrients
1. Which nutrients are abundant in oceans and
which are limiting factors?
2. Where are least nutrients found in the
ocean?
3. Where are most nutrients found in the
ocean and why?
4. How are nutrients in the ocean replaced?
(fact sheet)
Why is there a difference in productivity between open ocean and the continental shelf?
TASK complete the questions below
Table 1. compares
NPP figures of some
terrestrial ecosystems
with the oceans.
1.
2.
3.
4.
5.
Which types of ecosystem yield the greatest biomass?
Which ecosystem covers the smallest area of the earth?
Which column is the most useful in deciding which ecosystem is the most
productive?
Which ecosystem in the most productive and which is the least?
Explain the difference in NPP between open ocean and continental shelf. Use the
following factors to help you explain; light, turbidity, depth, nutrient availability.
Why is there a difference in productivity between open ocean and the continental shelf?
PLENARY TASK Complete the grid below. Look carefully at fig 14.1 on page 259 to help
Open Ocean
Description of
nutrient and
light
conditions
Reasons for
nutrient and
light
conditions
Continental shelf
Aquatic Food Production systems
2.Fishing Techniques
Key Questions.
1. What are the
factors controlling
marine
productivity?
2. Why is there a
difference in
productivity
between open
ocean and the
continental shelf?
Fishing Techniques- Pelagic or Demersal?
TASK make sure you know
the difference between
pelagic and demersal fish.
Give examples of each.
Instructions
• Complete the grid on the next slide.
• Use the textbook, subsequent slides and
websites to help you.
http://britishseafishing.co.uk/commercialfishing-methods/
http://www.mcsuk.org/downloads/fisheries/Fis
hingMethods.pdf
Fishing Techniques
Trawling
Including Midwater trawlers
Description of
technique
Selectivity of
the catch
Incl. named
species
Environmental
impacts
Energy inputs
Long-lining
Purse seining
Drift netting
Factory ships
Fishing Technology
Technique
Description
Problems
Surrounding net
Used for aggregated pelagic
• Bycatch e.g.
species e.g. tuna surround fish
dolphins
from the sides and from
• Discards
underneath, thus preventing the
(undersize
target species from escaping by
specimens, no
diving downwards.
marketable
specimens, non
target species)
Seine
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
• Bycatch/discards
especially if mesh
size small
Fishing Technology
Technique
Description
Problems
Bottom otter trawls
Cone-shaped net kept
open by otter boards
which is dragged across
the ocean floor
• Disturbance to
sediment
• Bycatch of fish and
non-fish species
Dredge
Heavy, metal structures,
sometimes with teeth to
scrape along or cut
through the bottom in
order to catch mussels,
scallops, oysters etc
• Sediment
compaction and
chemical changes
• Damage to reefs
• Bycatch
• Exposure of
organisms to
predation.
Here are some good clips to watch
about the impacts of commercial
fishing. They are on You tube so you
may have to watch them at home.
Make sure you do!
•
•
•
•
https://www.youtube.com/watch?v=nkfz5fOPSck
https://www.youtube.com/watch?v=IzrOuZ7cr1o
https://www.youtube.com/watch?v=sJpMPPX3vtE
Watch out for Trawlermen on TV