Grade 10 marine and fisheries technology – Fundamentals of Aquaculture Quiz
1. What is the best definition of aquaculture?
Aquaculture is the controlled husbandry and production (farming) of aquatic organisms, not the capture of wild fish or study of physical oceanography.
2. Which two fish species are most commonly farmed in Kenyan freshwater aquaculture?
In Kenya, freshwater aquaculture is dominated by Nile tilapia (Oreochromis niloticus) and African sharptooth catfish (Clarias gariepinus), which suit local conditions and markets.
3. What is a broodstock in fish farming?
Broodstock are selected mature fish maintained specifically for reproduction to produce eggs and milt for hatcheries.
4. Which term describes newly hatched fish that still feed on yolk or tiny plankton?
Fry are very young fish just after hatching; they later develop into fingerlings and then juveniles as they grow.
5. After the fry grow and are large enough to survive handling and transfer, what are they called?
Fingerlings are young fish that have grown past the fry stage and are suitable for stocking into grow-out ponds or cages.
6. What is the primary purpose of liming an earthen fish pond before stocking?
Liming neutralises acidic soils, raises pH, and supplies calcium, which helps plankton growth and overall pond productivity.
7. Which water quality parameter measures how acidic or alkaline pond water is?
pH indicates acidity or alkalinity of water; maintaining suitable pH (typically about 6.5–8.5 for many cultured fish) is important for fish health.
8. Why is dissolved oxygen important in aquaculture ponds?
Dissolved oxygen is essential for respiration of fish and microbes; low oxygen causes stress, poor growth, and mortality.
9. Which practice helps prevent the spread of disease when introducing new fish to a farm?
Quarantine allows time to detect and treat any disease in new stock before they mix with the main population, reducing disease spread.
10. What is polyculture in aquaculture?
Polyculture is the culture of two or more species together to use different niches and increase overall productivity when species are compatible.
11. Which method describes rearing fish inside net enclosures placed in lakes, reservoirs or the sea?
Cage culture uses nets or cages suspended in natural water bodies to contain and grow fish while allowing water exchange with the environment.
12. What does the feed conversion ratio (FCR) show in fish farming?
FCR measures feed efficiency: lower FCR means less feed is required to produce a kilogram of fish, which is economically important.
13. Which temperature range is generally suitable for optimal growth of Nile tilapia?
Nile tilapia grow best in warm tropical temperatures generally between about 24 and 30°C; too cold or too hot slows growth or causes stress.
14. What is the role of fertilising a pond with animal manure or inorganic fertilizers?
Fertilizers stimulate growth of phytoplankton and zooplankton, which are natural food for many fish species, improving natural pond productivity.
15. Which of the following is a safe habit for regular pond management?
Good record keeping helps farmers track performance, diagnose problems, and make better management decisions over time.
16. What is the main advantage of using a hatchery in aquaculture?
Hatcheries provide controlled breeding and rearing to produce uniform quantities of healthy fry and fingerlings for stocking grow-out systems.
17. Which practice will reduce oxygen depletion at night in a fertilised pond?
Aeration increases oxygen and avoiding excess fertilizer prevents plankton blooms that consume oxygen at night, reducing night-time depletion.
18. Which measurement indicates the clarity of water and can reflect plankton levels?
Secchi depth measures how deep a disk is visible in water and provides a simple indicator of turbidity and plankton concentration.
19. Which of the following is a basic sign that fish may be stressed or sick?
Gasping at the surface and poor feeding are common signs of low oxygen or disease stress and require immediate attention.
20. How often should small juvenile tilapia typically be fed on a small Kenyan farm for good growth?
Juvenile fish need frequent feeding (usually multiple times per day) to support fast growth; feeding regimes are adjusted as fish grow.
21. What is integrated aquaculture (integrated farming)?
Integrated systems recycle nutrients (for example, fish waste feeds crops or livestock), improving efficiency and sustainability on small farms.
22. Which worker safety practice is important when handling pond chemicals or feeds on a farm?
Safe handling with protective gear and following instructions prevents poisoning, injury, and contamination of the farm environment.
23. What does 'carrying capacity' of a pond mean for a fish farmer?
Carrying capacity is the sustainable stocking level where fish can grow without causing poor water quality, stress, or disease due to overcrowding.
24. Which action is useful to prepare a pond after draining and before restocking?
Drying and cleaning the pond and repairing structure reduces disease, improves water quality, and prepares a good environment for new stock.
25. Which of these is an example of a natural food in fertilised ponds?
Phytoplankton and zooplankton are microscopic natural foods that proliferate after fertilisation and are eaten by fry and some adult fish.
26. Why is proper stocking time (season) important when stocking ponds in Kenya?
Temperature and water availability vary by season in Kenya; stocking at suitable times improves survival, growth and farm efficiency.
27. What is aquaculture?
Aquaculture is the farming of aquatic organisms (fish, shellfish, algae) under controlled conditions, unlike capture fisheries which take animals from the wild.
28. Which of these is a common freshwater aquaculture species in Kenya?
Nile tilapia is widely farmed in Kenyan freshwater ponds and cages (e.g., in Lake Victoria) because it grows well in warm fresh water.
29. What is a 'fingerling' in aquaculture?
Fingerlings are juvenile fish that have grown past the larval stage and are suitable for stocking into ponds or cages for grow-out.
30. Which water parameter is most critical because fish need oxygen dissolved in water to breathe?
Dissolved oxygen is essential for fish respiration; low levels can cause stress or death, making it the most immediately critical parameter.
31. What does 'polyculture' in aquaculture mean?
Polyculture involves raising two or more species that use different parts of the environment, improving resource use and reducing risk.
32. Why is pH important in fish ponds?
pH affects metabolic processes, the toxicity of ammonia, and nutrient availability; extremes can harm fish and pond productivity.
33. What is the main purpose of aeration in ponds?
Aeration pumps oxygen into the water and helps circulate it, preventing low oxygen zones and keeping fish healthy.
34. Which feed component is most important for fish growth?
Protein provides amino acids necessary for tissue growth and repair; fish feeds are formulated to supply adequate protein for different species and stages.
35. What is a hatchery used for in aquaculture?
Hatcheries produce fry and fingerlings under controlled conditions to supply grow-out farms with healthy young stock.
36. Which practice helps reduce disease spread between ponds?
Biosecurity measures like disinfecting gear and controlling movement prevent pathogens from spreading between facilities.
37. What is carrying capacity in aquaculture?
Carrying capacity is the limit of fish biomass a system can sustain given water quality, oxygen, and feeding; exceeding it causes stress and disease.
38. Why is regular water exchange important in ponds?
Water exchange removes wastes like ammonia and restores dissolved oxygen and appropriate chemistry needed for fish health.
39. Which of these is a sign that fish might be sick?
Sick fish often separate from the group, breathe fast near the surface, or show sores and abnormal behaviour, indicating disease or poor water quality.
40. What is pond fertilization used for in traditional aquaculture?
Adding organic or inorganic fertilizers increases plankton and natural food production, supporting growth of filter-feeding or young fish.
41. Which culture system keeps fish in net enclosures within a lake or reservoir?
Cage culture uses nets or cages suspended in open water bodies (like Lake Victoria) to grow fish while water flows through the cages.
42. Why are broodstock important in aquaculture?
Broodstock are selected adults maintained to provide quality eggs and sperm for hatcheries, ensuring good genetics and production.
43. What does 'monoculture' refer to in fish farming?
Monoculture means raising a single species in a pond or cage, which simplifies management but may increase disease risk if problems occur.
44. Which of the following is a basic step in preparing an earthen pond before stocking fish?
Proper pond preparation includes draining and drying to remove predators and silt, and applying lime to adjust pH and improve conditions for stocking.
45. What is a common low-cost feed ingredient used by smallholder fish farmers in Kenya?
Small-scale farmers often use locally available plant by-products (maize bran, oilseed cakes) blended to supply protein and energy for fish feeds.
46. How does stocking density affect growth in aquaculture?
Overcrowding leads to competition for oxygen and food, increases waste, and raises stress and disease incidence, reducing individual growth.
47. Which practice helps make aquaculture environmentally sustainable?
Sustainable practices (efficient feeding, correct stocking, effluent treatment) reduce pollution, conserve resources, and protect surrounding ecosystems.
48. What is the role of a biofilter in a recirculating aquaculture system (RAS)?
Biofilters host nitrifying bacteria that transform ammonia (toxic) into nitrate, helping maintain safe water chemistry in RAS systems.
49. Why is record keeping important on a fish farm?
Good records help farmers monitor performance, find problems early, plan feeding and harvests, and improve productivity and profitability.
50. Which seaweed is commonly grown in Kenyan coastal areas for income and food?
Eucheuma and Gracilaria are tropical seaweeds cultivated along the Kenyan coast for food, carrageenan, and local livelihoods.
51. What is an advantage of cage culture over earthen ponds in Lake Victoria?
Cage culture uses open water for production, requiring less land and allowing higher production on lakes like Victoria while relying on natural water exchange.