Grade 10 marine and fisheries technology – Fish Pond Quiz

A good pond site needs reliable clean water and must not be flood-prone; steep slopes, polluted areas or saline soils will cause management problems and poor fish survival.

Nursery ponds are shallow, protected ponds used to rear fry and small fingerlings until they are large enough to be moved to grow-out ponds.

Most freshwater fish do best in near-neutral to slightly alkaline water; pH 6.5–8.5 supports good biological function and plankton production.

Daytime DO above about 5 mg/L is desirable for good growth and health; very low DO (2–3 mg/L or less) can stress or kill fish.

Lime is used to correct acidic soils and water, improving alkalinity and calcium levels which supports plankton growth and pond fertility.

Feeding should follow recommended rates based on fish size and appetite to avoid underfeeding or overfeeding, which wastes feed and harms water quality.

Polyculture uses different species that feed at different levels (e.g., surface and bottom feeders) so the pond's food resources are used more efficiently, increasing total yield.

Nile tilapia is hardy, fast-growing and widely adapted to Kenyan ponds, making it the most common cultured freshwater species in the country.

Aerators mix air into the water, raising dissolved oxygen which is essential for fish respiration and overall pond health.

Stocking density describes how many fish are placed in a given pond space, commonly reported per cubic metre or per hectare to guide management.

Drying ponds helps remove pests and predators, lets the soil oxidize and makes it easier to repair liners or embankments before restocking.

Disease often causes reduced feeding, erratic swimming, lethargy or visible sores; faster growth and vivid colours are not disease signs.

Harvesting is done when fish reach the desired size for market to maximize profit and ensure good product quality.

Broodstock are selected mature fish kept specifically for breeding to supply hatcheries or nursery ponds with healthy fry and fingerlings.

Organic fertilizers supply nutrients that encourage plankton and natural food production; when used correctly they support fish growth (overuse can, however, harm water quality).

Inlets and outlets allow the farmer to manage water levels, replace water, control flow rate and drain the pond for harvest or maintenance.

A depth of roughly 1.5–2.5 m is common for grow-out ponds as it balances temperature stability, oxygenation and ease of management; very shallow or extremely deep ponds are not suitable.

Keeping records of stocking, feeding, growth, mortality and costs allows the farmer to evaluate performance, detect problems early and improve production.

FCR shows how efficiently fish convert feed into body weight; lower FCR means better feed efficiency and lower production costs.

Applying fertilizer after filling and before stocking gives time for plankton (natural food) to increase so fry or fingerlings have food when stocked.

Quarantine isolates new fish to detect and treat diseases before they can spread to the main population, protecting the farm's health status.

Hapas are small mesh net enclosures placed in ponds to protect young fish from predators and allow easy feeding and grading.

Carrying capacity refers to how much fish weight the pond ecosystem (food, oxygen, waste removal) can support without causing collapse in performance or water quality.

Herons are wading birds commonly found near ponds and can catch and eat fish, causing significant losses if ponds are not protected.

Water exchange replaces polluted or depleted water with fresh water, helping to control nutrient buildup and keep oxygen and other quality parameters within healthy ranges.

Heavy clay soils have low permeability so they retain water, making them suitable for earthen ponds. Sandy, rocky or very peaty soils leak or collapse and are unsuitable without lining.

Tilapia do best when dissolved oxygen is maintained above about 5 mg/L. Levels below 3 mg/L cause stress and mortality. Very low values like 0.5–1 mg/L are dangerous.

A pH between about 6.5 and 8.5 is suitable for most pond fish (including tilapia and catfish). Very acidic or very alkaline water harms fish and reduces productivity.

Lime is used to raise pH and supply calcium, improving water quality and plankton growth. It does not make water salty or change temperature significantly.

Fry are newly hatched young; fingerlings are older juveniles that are bigger and have developed fins and scales, suitable for stocking grow-out ponds.

A depth around 1.2–1.8 m (about 1.5 m) is commonly recommended for small earthen grow-out ponds to provide stable temperatures and oxygen distribution. Extremely shallow or very deep ponds are impractical.

Stocking density describes how many fish are placed in a given area (e.g., per m2) or volume (per m3). It affects growth, water quality and carrying capacity.

Gates and drains let farmers manage pond water levels for maintenance, water exchange, draining for harvest or emergency situations. They do not affect taste or purposely attract insects.

Fertilizers (organic or inorganic) stimulate plankton growth, providing natural food for fry and fingerlings. Fertilizers do not disinfect or alter species directly.

Feeding 2–3 times daily with appropriate rations helps growth and reduces waste. Infrequent or unmeasured large feedings cause poor growth and water quality problems.

Quarantining new stock allows detection and treatment of disease before mixing with existing fish. Bringing in unchecked materials or mixing fish increases disease risk.

Wading and predatory birds frequently take fish from ponds; farmers use nets or scare devices. Cats may take some fish but birds are a major predator; plants and dikes do not prey on fish.

Hapas or nurseries protect and feed fry until they reach fingerling size suitable for stocking grow-out ponds. They are not for long-term adult storage or crop cultivation.

Harvesting should be done when fish have reached the desired size and weight for market. Harvesting too early or in unsuitable weather risks low yield or fish loss.

Mechanical aeration increases oxygen levels, improving fish survival and feed efficiency. Aerators do not salt or intentionally overheat water and are used to reduce, not attract, pests.

Polyculture combines species that occupy different niches (e.g., tilapia with catfish) to use resources efficiently. It is not keeping one fish alone or indoor single-tank culture.

Sick fish often stop feeding and show unusual behaviour (e.g., gasping, corkscrewing). Healthy activity and feeding are signs of good health, not disease.

Carrying capacity refers to the highest fish biomass that the pond can sustain given its water quality and feeding regime. Exceeding it leads to poor growth and mortality.

FCR = feed offered divided by weight gained. A lower FCR means more efficient feed use. It is not related to net catches or physical pond measures.

Lime rates are based on initial soil acidity (pH) and the pond area/volume. Farmer observations and soil tests guide correct application rates.

Dikes form the pond perimeter, holding water and often providing walkways or space for equipment. They are not feeding devices and proper design can reduce, not increase, mosquito problems.

Clean, consistent water such as borehole or spring water reduces disease and chemical risks. Contaminated runoff, sewage or stagnant garbage water can introduce pollutants and pathogens.

Applying fertilizer shortly before stocking allows natural food organisms to grow, improving survival of fry/fingerlings. Applying at harvest or during drying is not useful.

Sampling every 2–4 weeks gives useful information on growth rates and feed needs without stressing the fish too much. Very infrequent or excessive sampling is impractical.

All-male tilapia do not reproduce in the pond, so energy goes to growth rather than breeding, reducing overcrowding and improving marketable yield. It does not change colour or remove feeding needs.