Question 23M.3.SL.TZ1.12
| Date | May 2023 | Marks available | [Maximum mark: 4] | Reference code | 23M.3.SL.TZ1.12 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Evaluate, State | Question number | 12 | Adapted from | N/A |
The feed conversion ratio (FCR) of grouper fish, Epinephelus coioides, was compared at two different fish densities in two types of tanks over a period of 10 weeks. The recirculation tank reused the same water, which was constantly purified. The flow-water tank had a continuous flow of clean water.
[Source: Samad, A., Nan, F.-H. and Lee, M., 2014. Effects of stocking density on growth and feed utilization of grouper
(Epinephelus coioides) reared in recirculation and flow-through water system. African Journal of Agricultural Research,
[e-journal] 9(9), pp. 812–822. https://doi.org/10.5897/AJAR2013.7888. Open access.]
State the effect of increasing fish density on feed conversion ratios.
[1]
(FCRs) decrease;
This was mostly answered correctly; some compared the two types of tanks instead of density.
Evaluate the rearing of grouper fish as food for humans at high density using recirculation tanks rather than water-flow tanks.
[3]
Pros:
a. less water is wasted (as it is purified and re-used);
b. less impure water is released to the environment;
Cons:
c. (FCR with recirculation tanks) has higher feed conversion ratio;
d. more food/energy needs to be supplied (to the fish)
OR
recirculation may cost more;
Accept vice versa for water flow
Pro or con need not be stated
The command term "evaluate" was not understood, such that pros and cons were not given and 3 marks were not awarded. The concept of FCR was rarely understood and although candidates were awarded mpc for the recirculation tank having a higher FCR, they considered this was an advantage.
