Chapter 2: Perform fish farm management practices

Fish farming in Kenya represents a vital component of agricultural diversification and food security enhancement. Effective management of fish farms ensures sustainable production, maximizes yields, and safeguards the health of cultured species. This chapter focuses on essential management practices necessary for successful fish farming, equipping Agriculture and Extension professionals with knowledge to support farmers in optimizing their operations. Understanding these practices is crucial for increasing fish production and improving livelihoods in rural and peri-urban communities.

2.1 Fish farm management practices

Fish farm management is the systematic organisation, operation and supervision of fish culture activities to achieve good productivity. It covers the practices that keep fish healthy and growing, protect the environment and keep the enterprise profitable. In Kenya smallholder pond farmers and larger commercial farms with tanks and cages work side by side, and efficient management is what allows both to meet the growing demand for fish. This topic explains the terms used in fish farm management, why management matters and the main practices carried out on the farm, while the records that support them and the practical work are taught in the later topics of this outcome.

2.1.1 Definition of terms

These are the terms a fish farm worker uses when planning and carrying out management practices. Each should be understood before the practices themselves are studied.

• Aquaculture: The controlled cultivation of aquatic organisms such as fish, crustaceans and plants in fresh or salt water. Fish farming in ponds, tanks and cages is a branch of aquaculture.
• Rearing unit: Any structure that holds fish while they grow, such as a pond, a tank, a hapa or a cage.
• Stocking density: The number of fish introduced per unit area or volume of water. Example: 600 fingerlings put into a pond of 200 m² give a stocking density of 600 ÷ 200 = 3 fingerlings per m². The right density balances growth and water quality, because overcrowding causes stress and low oxygen.
• Feed conversion ratio (FCR): The weight of feed given divided by the weight gained by the fish. Example: if a farmer feeds 150 kg of feed and the fish gain 100 kg, the FCR is 150 ÷ 100 = 1.5. A lower value means that the fish convert feed to body mass more efficiently.
• Water quality parameters: The measurable properties of the water that affect fish health, such as temperature, dissolved oxygen, pH, transparency and ammonia.
• Dissolved oxygen: The oxygen present in the water that the fish breathe, measured in milligrams per litre (mg/L).
• Biosecurity: The set of measures that keep disease-causing organisms away from the farm and stop them from spreading within it.
• Quarantine: The separate holding of newly bought or sick fish until they are known to be healthy.
• Predator: An animal that feeds on the fish, such as a heron, kingfisher, otter or snake.
• Parasite: An organism that lives on or in a fish and feeds at its expense, for example fish lice and gill flukes.
• Effluent: Water that leaves a pond or tank, often carrying uneaten feed, faeces and dissolved wastes.
• Sludge: The layer of mud, uneaten feed and faeces that settles on the bottom of a pond or tank.
• Harvesting: The collection of mature fish from the rearing unit for sale or consumption. Timely harvesting affects profit and fish quality.

2.1.2 Importance of fish farm management

Good management turns a stocked pond into a profitable enterprise. It reduces losses, uses inputs wisely and protects the environment on which the farm depends.

• Maximising growth and yield: Balanced feeding, suitable stocking density and good water quality promote healthy growth and increase the weight harvested from each rearing unit.
• Preventing disease outbreaks: Regular observation, clean water and biosecurity measures reduce the diseases that can destroy a stock and the money invested in it.
• Improving use of resources: Careful use of feed, water and labour lowers the cost of producing each kilogram of fish and improves returns, especially for small-scale farmers.
• Promoting environmental sustainability: Good management reduces pollution of water and the damage to the surroundings, and it helps the farm to comply with the environmental rules enforced by the National Environment Management Authority (NEMA).
• Supporting market competitiveness: Regular production of healthy fish of uniform size lets the farmer supply traders, hotels and markets throughout the year and meet the quality they ask for.
• Protecting workers and the public: Safe handling of chemicals, waste and fish keeps workers healthy and ensures that the fish sold are safe to eat.

2.1.3 Fish management practices

Fish management practices are the regular activities that keep the water, the rearing units and the fish in good condition from stocking to harvest. They are carried out by observation and routine, so that a problem is noticed while it is still small. Four of them are treated in detail below, and the other routine practices follow after them.

2.1.3.1 Checking water quality parameters

Fish live in their water and breathe, feed and pass wastes into it, so the state of the water decides their health and growth. Checking water quality parameters means measuring them at regular times, comparing the readings with the suitable range and taking action when a reading moves out of range. Many problems on a fish farm start with water quality, and the first signs are often seen in the fish themselves, such as gulping at the surface.

• Timing: Measure oxygen early in the morning, when it is lowest, and temperature in the afternoon, when it is highest.
• Sampling points: Take samples at the same places and depths each time, away from the inlet, so that readings can be compared.
• Warning signs: Fish gulping at the surface at dawn, fish that stop feeding, dead fish and water that turns dark or smells bad all show that water quality needs urgent attention.
• Catfish: African catfish tolerate low oxygen better than tilapia because they can breathe air, but they still grow best in well-oxygenated water.
• Recording: Write each reading in the water quality record so that trends are seen early.

2.1.3.2 Rearing units’ maintenance practices

Rearing units wear out and fill with silt, weeds and wastes, and a poorly kept unit loses water, harbours predators and disease and produces fewer fish. Maintenance is done on a routine, with larger jobs carried out between production cycles when the unit is empty.

• Pond walls: Keep them firm, so that water is not lost and cattle or machinery do not break them down. Plant short grass to prevent erosion.
• Weed control: Cut aquatic weeds and tall grass on the edge by hand, because dense weed uses up oxygen at night and shelters snakes and frogs.
• Removing sludge: Remove the layer of mud and waste from the bottom of the pond when it is dry, because it uses oxygen and can carry disease.
• Screens and pipes: Keep mesh screens on inlets and outlets in good repair so that wild fish cannot enter and stock cannot escape.
• Drying and liming: Dry the pond bed in the sun between cycles and apply lime as advised, to kill pathogens and correct acidity before restocking.
• Cleaning equipment: Wash and dry nets, buckets and basins after each use, and keep separate equipment for sick fish.

2.1.3.3 Control of predator, parasite and diseases

Predators, parasites and diseases all reduce survival and growth, and prevention is cheaper and more reliable than treatment. The farmer checks the fish often, acts at the first sign of trouble and keeps the water and the rearing units clean.

• Predators: Herons, kingfishers, otters, snakes, monitor lizards, frogs and insect larvae feed on fish, especially fingerlings. Nets, scare devices and fences keep most of them out, and the devices are described in the topics on predator control devices. Remove wild fish that enter the pond, and keep the grass short around the edges so that predators have no cover.
• Parasites: External parasites such as fish lice, anchor worms and gill flukes attach to the skin and gills, and internal worms live in the gut. Infested fish rub against pond walls, produce excess mucus, swim weakly and have pale or damaged gills.
• Bacterial and fungal diseases: Bacteria cause red sores, swollen bellies and fin rot, while fungus appears as white or grey cotton-like patches on injured skin and on eggs. These diseases usually follow stress, poor water quality or rough handling.
• Early detection: Watch the fish at feeding time, because sick fish eat less, separate themselves from the group or swim abnormally. Remove dead fish at once and note their number.
• Prevention: Buy fingerlings from a reliable hatchery, quarantine new stock, avoid overcrowding, give good feed, keep the water clean and disinfect nets and tools between ponds.
• Isolation and treatment: Move sick fish to a separate tank, and treat only on the advice of a fisheries officer or a veterinarian, using the product, dose and time stated on the label.
• Withdrawal period: Do not harvest fish for sale until the period required after a treatment has passed, so that the fish are safe to eat.
• Between cycles: Drain, dry and lime the pond to break the life cycle of parasites and disease organisms before restocking.

2.1.3.4 Waste management

A fish farm produces wastes that must be handled so that they do not pollute water, spread disease or attract pests. The main wastes are uneaten feed and faeces, pond effluent, sludge, dead fish and the packaging and containers used on the farm. Good waste management also saves money, because less feed wasted means lower costs.

• Reducing waste at source: Feed only what the fish eat in a few minutes and adjust the amount to their size and appetite, because uneaten feed rots in the water and uses oxygen.
• Treating effluent: Let water from the ponds pass through a settling pond or a vegetated ditch before it leaves the farm, so that solids settle and plants take up nutrients. The Environmental Management and Co-ordination Act, 1999 and its regulations on water quality require that discharged water does not pollute rivers and lakes.
• Using sludge: Dry sludge and pond mud can be spread on vegetable plots and crop fields, where the nutrients feed the plants. Do not wash it into streams.
• Disposing of dead fish: Remove dead fish daily and bury them in a pit with lime, well away from water sources, or burn them. Never throw them into the pond or into a river, because they spread disease.
• Handling chemicals and used oil: Keep chemicals, fuel and used oil from pumps and engines in labelled closed containers in a lockable store, and take them to an authorised collector. Hazardous waste is kept apart from ordinary waste.
• Sharps: Used needles and syringes are discarded in a sharps container and never reused or put with ordinary waste.
• Packaging: Reuse or sell empty feed bags where possible, collect plastics and do not burn them in the open or leave them in the pond area.

Other routine management practices

Several other practices complete the management routine and link the four above to the full production cycle.

• Pond preparation and maintenance: Before stocking, drain and dry the pond, lime it, fill it slowly through a screen and let the water settle so that natural food develops.
• Stocking with quality fingerlings: Use healthy, uniform, disease-free fingerlings of a species suited to the local climate and water, and stock them at the planned density.
• Feeding management: Give nutritionally balanced feed in the correct quantity and at regular times, so that growth is good and little feed is wasted. Formulated feeds usually give better growth than farm scraps.
• Records: Keep written records of stocking, feeding, growth, mortality, water quality and sales, which are covered under the preparation of fish management records.

Chapter Summary

This chapter on fish farming focused on essential fish farm management practices, beginning with the definition of key terms that clarify concepts used throughout the unit. The importance of effective fish farm management was emphasized, highlighting its role in ensuring healthy fish growth and sustainable production. Detailed fish management practices were explored, including the regular checking of water quality parameters to maintain an optimal aquatic environment. Maintenance of rearing units was discussed as a critical activity to prevent structural failures and contamination. The chapter also covered strategies for controlling predators, parasites, and diseases that can adversely affect fish stocks. Waste management practices were addressed to promote environmental sustainability and reduce health risks. Additionally, the preparation of fish management records was explained as a vital tool for monitoring farm activities and making informed decisions. Finally, practical steps for carrying out fish management practices and accurately preparing management records were presented to support efficient farm operations.