Question 1
(a) State one observable difference between specimens A and B. [ 1 mark ]
(b) Give one reason for the observed difference between specimens A and B. [ 1 mark ]
(c) Which of the specimens A and B is more suitable for the culture of table fish? [ 1 mark ]
(d) Give two reasons for the answer in 1(c). [ 2 marks ]
(e) Describe five ways by which the quality of the less suitable specimen could be improved for table fish production. [ 10 marks ]
Observation
This question was fairly attempted by the candidates. Although, most of the candidates were able to state an observable difference between specimens A (Fish pond water) and B (Tap water) with reason as required in 1(a-b), majority of them were unable to state with reason which of specimens A (Fish pond water) and B (Tap water) is more suitable for the culture of table fish as required in 1(c-d). Also, in 1(e), most of the candidates could not describe the ways of improving the quality of specimen B (Tap water) for table fish production.
The expected answers were:
1(c) Specimen more suitable for the culture of table fish
Specimen A (Fish pond water).
(d) Reasons for the answer in 1(c)
- It has natural fish food/nutritious/rich in nutrients/has fish food/has plankton
- Presence of plankton improves oxygenation/presence of plankton improves
aeration/aerates the water/adds oxygen to water.
- Presence of plankton increases productivity in fish pond water.
- It provides good environment for fish culture/good culture medium for fish.
(e) Ways to improve quality of specimen B (Tap water) for table fish
production
Application of fertilizer/inorganic fertilizer/organic fertilizer/manure
- Could be broadcast/spread/bagged in the water.
- It increases nutrient content/improves plankton growth/increase fish food.
- Increases primary productivity of pond.
Liming/application of lime ( It could be done before or after impounding)
- Creates a suitable pH for growth of fish.
- Liberates nutrient.
- Keeps the water free of pathogens/parasites.
- Creates suitable environment for fish food to grow.
Aeration/addition of oxygen/oxygenation
- Increases dissolved oxygen which improves the quality of water.
- It could be done by using aerator/ splashing the water surface with stick/paddling.
Inoculation / Addition / introduction of plankton /algae /zooplankton / microphytes / phytoplankton
- If conditions are favourable, these planktons will flourish thereby improving the
quality of water.
Dechlorination/ removal of chemical (chlorine)
- Leave water for chlorine/chemical to escape/expose water in the open air.
- Stir continuously for chlorine/chemical to escape.
- Delay stocking.
Exposure to sunlight
- Wind will blow algae spores into the water which will then grow and spread in
the water.
- Oxygen will dissolve into the water.
- Other fish food organisms will be attracted into the water.