Aquatic Food Production systems1.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. Biomass2. Net Primary Productivity3. Algae4. Phytoplankton5. algal blooms6. Photic layer7. Upwelling8. Ocean salinity9. Ocean density10. Ocean thermocline

What are the factors controlling marine productivity?

Light1. 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 20-30

metres? (Fact Sheet)

TASK Use pages 258 and 9 to answer the following questions

What are the factors controlling marine productivity?TASK Use pages 258 and 9 to answer the following questions

Nutrients1. 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)

1. Which types of ecosystem yield the greatest biomass?2. Which ecosystem covers the smallest area of the earth?3. Which column is the most useful in deciding which ecosystem is the most

productive?4. Which ecosystem in the most productive and which is the least?5. Explain the difference in NPP between open ocean and continental shelf. Use the

following factors to help you explain; light, turbidity, depth, nutrient availability.

Table 1. compares NPP figures of some terrestrial ecosystems with the oceans.

Why is there a difference in productivity between open ocean and the continental shelf?

TASK complete the questions below

PLENARY TASK Complete the grid below. Look carefully at fig 14.1 on page 259 to help

Open Ocean Continental shelf

Description of nutrient and light conditions

Reasons for nutrient and light conditions

Why is there a difference in productivity between open ocean and the continental shelf?

Aquatic Food Production systems2.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/commercial-fishing-methods/http://www.mcsuk.org/downloads/fisheries/FishingMethods.pdf

Fishing Techniques

Trawling Including Midwater trawlers

Long-lining Purse seining Drift netting Factory ships

Description of technique

Selectivity of the catch

Incl. named species

Environmental impacts

Energy inputs

Fishing Technology

Technique Description ProblemsSurrounding net

Seine

Used for aggregated pelagic species e.g. tuna surround fish from the sides and from underneath, thus preventing the target species from escaping by diving downwards.

• Bycatch e.g. dolphins

• Discards (undersize specimens, no marketable specimens, non target species)

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 ProblemsBottom otter trawls

Dredge

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

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