Chapter 3: Manage fish hatcheries

Fish farming is a vital component of Kenya's agricultural sector, contributing significantly to food security, income generation, and employment, especially in rural areas. Efficient management of fish hatcheries ensures a reliable supply of quality fingerlings, which is crucial for successful fish production in cages and ponds. This chapter focuses on the principles and practices of managing fish hatcheries and fish cages, tailored for Agriculture and Extension professionals who support smallholder and commercial fish farmers across the country.

3.1 Fish hatchery management

A fish hatchery is a facility where fish are bred, their eggs are incubated and hatched, and the young are reared to fry or fingerlings before they are moved to grow-out ponds, tanks or cages. Good hatchery management supplies healthy, uniform fingerlings to the farm and to neighbouring smallholders, and it protects the quality of the broodstock. A farm that buys poor fingerlings loses time and feed on fish that grow slowly or die, so the hatchery is where the success of a production cycle is largely decided. In Kenya hatcheries rear species such as Nile tilapia and African catfish and are run by individual farmers, groups and larger companies. This topic introduces the terms of hatchery work and the tools and equipment that a hatchery uses, while pre-stocking, broodstock and records are taught in the later topics of this outcome.

3.1.1 Definition of terms

These are the terms a hatchery worker uses every day. Each should be understood before the tools and equipment are studied.

• Hatchery: A facility for breeding fish, incubating eggs and rearing larvae and fry up to fingerling size.
• Broodstock: Mature fish kept for breeding, selected for health, growth and good form.
• Spawning: The release of eggs and milt by the female and male fish, either naturally or after hormone treatment.
• Milt: The fluid from a male fish that contains the sperm.
• Fertilisation: The joining of egg and sperm to form an embryo, which in a hatchery may take place naturally or after the eggs and milt have been mixed by hand.
• Incubation: The period when fertilised eggs develop under controlled water flow, temperature and oxygen until they hatch.
• Hatching rate: The percentage of fertilised eggs that hatch, calculated as the number hatched divided by the number of fertilised eggs, multiplied by 100. Example: if 800 of 1,000 fertilised eggs hatch, the hatching rate is 800 ÷ 1,000 × 100 = 80 percent.
• Larva: The newly hatched fish, which still carries a yolk sac and does not yet feed on external food.
• Fry: A young fish that has used up its yolk sac and has started to feed on external food.
• Fingerling: A young fish that has grown to about the length of a finger and is ready for stocking into grow-out units.
• Hapa: A fine-meshed net enclosure placed in a pond to hold broodstock, eggs or fry.
• Rearing tank: A container of concrete, fibreglass or plastic used to hold fry and fingerlings under controlled conditions before they are moved to larger units.
• Aeration system: Equipment such as an air pump with tubing and air stones that adds oxygen to the water, which helps eggs, larvae and fry to survive.

3.1.2 Hatchery management tools and equipment

Hatchery work needs small, accurate tools that handle fish and eggs without harm. The table lists those in common use. Specifications depend on the species and on the size of the hatchery.

3.1.2.1 Uses of hatchery management tools and equipment

Each tool has a task in the hatchery sequence, and using the wrong tool can damage eggs or injure the broodstock.

• Holding and moving fish: Hapas keep broodstock and young fish separate, and soft knotless nets move them without damaging their scales or fins. Nets must be handled gently when fry are transferred.
• Incubating eggs: Trays and jars hold the eggs while a gentle flow of clean water brings oxygen and carries wastes away.
• Supplying oxygen: Air pumps and air stones keep the dissolved oxygen high in crowded tanks, which is important at night and in warm weather.
• Moving water: Pumps circulate and supply water to tanks and incubation units, and they must give a steady flow.
• Cleaning tanks: Siphoning tubes draw uneaten feed and waste from the tank floor without disturbing the fish.
• Checking the water: Thermometers and oxygen and pH meters show whether the water is suitable before eggs or larvae are added. Stable temperature is critical for the correct development of the eggs.
• Weighing and sampling: Scales record the mass of broodstock and sampled fingerlings, which guides feeding and the quantity of hormone given.
• Giving hormone: Single-use syringes and needles inject spawning hormone at the dose set for the weight of the fish, and each needle is used once and then discarded in a sharps container.
• Inspecting eggs: A hand lens or microscope shows whether eggs are fertilised and whether fungus is present.

3.1.2.2 Maintenance of hatchery management tools and equipment

Dirty or damaged equipment carries disease and damages eggs, so every item is cleaned and checked after use. A simple routine keeps equipment ready for the next breeding cycle.

1. Rinse nets, trays, jars and buckets with clean water after use to remove eggs, slime and debris. Clean incubation trays regularly to prevent fungal infection of eggs.
2. Disinfect them at the strength recommended on the product label, soaking them for the stated time and then rinsing them well with clean water.
3. Dry nets and trays in the shade and store them off the ground, away from sunlight, chemicals and rodents.
4. Check hapas and hand nets for holes and repair or replace them before they are used again.
5. Calibrate meters with the solutions supplied, rinse the probes and store them as the maker instructs.
6. Service pumps and air pumps by cleaning inlet filters, checking the impeller, replacing worn tubing and air stones, and checking electrical connections, so that the water flow stays steady.
7. Empty, scrub and dry tanks and troughs between batches, and check outlets and drains for blockage.
8. Discard single-use syringes and needles in a sharps container, and never clean them for reuse.
9. Keep a log of cleaning, repairs and replacements, so that missing or worn items are noticed early.

Chapter Summary

This chapter focuses on the effective management of fish hatcheries and fish cages, essential components of successful fish farming. It begins by exploring fish hatchery management, emphasizing the importance of maintaining optimal environmental conditions to ensure high survival rates of fish eggs and larvae. Proper feeding, water quality control, and disease prevention are highlighted as critical practices for hatchery success. The chapter also addresses the setup and maintenance of fish cages, detailing the selection of appropriate cage materials and strategic placement in water bodies to maximize fish growth. Managing stocking densities and regular monitoring of fish health within cages are discussed to prevent overcrowding and disease outbreaks. Overall, the chapter provides comprehensive guidance on integrating hatchery and cage management techniques to enhance productivity and sustainability in fish farming operations.