A coastal fish farm uses floating sea cages to rear salmon. Fig. 1 shows a cross-section through one cage. Workers add measured amounts of pellet food each ...
Question 1 Report
A coastal fish farm uses floating sea cages to rear salmon. Fig. 1 shows a cross-section through one cage. Workers add measured amounts of pellet food each day and inspect the fish for disease. Nets stop the fish escaping, but water can move through the cage. The farm manager wants rapid fish growth without causing pollution in the surrounding area.
(a) Describe two features of the cage that allow the salmon to remain alive. [2]
(b) Explain why uneaten food and fish faeces may reduce the number of organisms living on the sea bed below a cage. [2]
(c) State two ways the farm could reduce the spread of disease between fish in the cage. [2]
Answer Details
(a) The net prevents salmon escaping. Water moves through the cage, providing oxygen and removing wastes. [2]
(b) Uneaten food and faeces increase the organic matter or nutrient concentration below the cage. Decomposers break down this waste and use oxygen, leaving less oxygen for sea-bed organisms, so fewer can survive. [2]
(c) Two suitable measures are to isolate infected fish and vaccinate fish. Reducing stocking density, disinfecting equipment, promptly removing dead fish, and preventing sharing of contaminated equipment are also valid. [2]
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