Topic 12: The Extent To Which Aquaculture Can Replace Fishing

Question 1

Why may the reliance on aquaculture increase, and the catch from it equal that from wild fish?

Answer 1

There has been no further increase in global fish catches since 1990
That was after 50 years of increasing catches
Increasing demand for seafood, increased the need for the expansion of aquaculture

Question 2

What 3 problems need to be solved in order to for large scale aqua culture to be sustainable?

Answer 2

Tropic level efficiency
Food requirements
Stock collection

Question 3

Trophies level efficiency

Answer 3

It is more productive to raise herbivorous fish species because the amount of food produced per unit area is higher e.g. tilapia
However, carnivorous fish, although less energy-efficient are more popular with customers, eg. Salmon
Fish have a low basal metabolic rate because they dont use a lot of energy for warmth or support, so have higher food conversion ratios than mammals or birds

Question 4

Food requirements for herbivorous fish

Answer 4

May eat plants and algae that naturally grow in the water
Growth of these can be increased by adding plant nutrients
Supplementary feeding may involve adding plant material e.g. crop waste

Question 5

Food requirements for carnivorous fish

Answer 5

E.g. salmon may feed on fish that have a lower economic value e.g. fish meal from sandeels
Overfishing of sandeels has caused population decline in other species that eat them e,g, puffins
Some plant based foods have been developed but the fish meat then produced is less tasty

Question 6

Stock collection

Answer 6

Some species do not breed well in captivity
E.g. Atlantic blue fin tuna
So young fish are caught in the sea, then raised in large cages int he sea
So tuna aquaculture cannot continue without a wild population