4.3 Aquatic food production systemsIB Environmental Systems and Societies SL: Subtopic test

1. 1
   In the sea lochs of western Scotland, Atlantic salmon are reared in floating net pens. The fish are fed pellets made partly from wild-caught fish. Waste feed and faeces fall to the seabed beneath the pens, and escaped farmed salmon sometimes breed with wild salmon in nearby rivers. The industry has grown rapidly and employs many people in remote coastal communities.

   (a)

   Which statement correctly defines aquaculture?

   [1 mark]

   • AThe farming of aquatic organisms, including fish, molluscs, crustaceans and aquatic plants
   • BThe harvesting of wild fish from the open ocean using nets and lines
   • CThe protection of fish stocks inside marine protected areas
   • DThe collection of plankton to use as fertiliser

   (b)

   Which of the following is an environmental impact of salmon farming described in the scenario?

   [1 mark]

   • AIt reduces the nutrient content of the water around the pens
   • BIt guarantees a recovery of wild salmon stocks
   • CEscaped farmed fish can interbreed with wild salmon and reduce the genetic diversity of wild populations
   • DIt removes all pressure on wild fish stocks

   (c)

   Outline two reasons why the aquaculture industry is expanding.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Average fish consumption per person has risen steadily across the world over recent decades. Fisheries scientists estimate, for each fish stock, the maximum sustainable yield (MSY). Governments in many regions set annual quotas that limit the total catch, and some campaigns encourage consumers to choose fish from sustainable sources.

   (a)

   Which pair of factors best explains the rising global demand for seafood?

   [1 mark]

   • AFalling world population and a decrease in the price of meat
   • BRising fish stocks and a ban on fishing quotas
   • CIncreased use of aquatic fertilisers and more marine reserves
   • DGrowth in the human population and changes in dietary preferences

   (b)

   What is the maximum sustainable yield (MSY)?

   [1 mark]

   • AThe largest number of fish a boat can carry
   • BThe highest annual catch that can be taken from a stock and sustained over time
   • CThe total number of fish in a stock
   • DThe lowest catch needed to keep fishers employed

   (c)

   Explain why setting a fishing quota above the MSY can lead to the collapse of a fish stock.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Records from a fictional bottom-dwelling fish stock in a shelf sea show the following. Year 1: catch 90,000 tonnes, 500 boats fishing. Year 5: catch 60,000 tonnes, 750 boats. Year 10: catch 30,000 tonnes, 1,000 boats. Over the period the average size of fish landed fell, and many of the fish caught were young.

   (a)

   Calculate the percentage decrease in catch between year 1 and year 10, and use catch per boat to show what has happened to the fish stock.

   [3 marks]

   (b)

   Suggest two measures that managers could introduce to restore the fishery, explaining how each would work.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   For centuries the Grand Banks off Newfoundland, Canada, supported huge catches of Atlantic cod. After the Second World War, large industrial trawlers with sonar and freezer facilities fished the Banks. Catches peaked in the 1960s and then fell. In 1992 the Canadian government closed the northern cod fishery, and tens of thousands of fishers and plant workers lost their jobs. Cod stocks have been slow to recover.

   (a)

   Explain how overexploitation led to the collapse of the Grand Banks cod fishery and the consequences of the collapse.

   [6 marks]

   (b)

   Evaluate the use of marine protected areas, fishing legislation and changes in consumer behaviour as ways of making fisheries more sustainable.

   [6 marks]

   Total for question 4: 12 marks

End of questions