If you want to raise fish, you need a supply of young fish. You can raise your own baby fish instead of buying them or catching them in the wild.
Newly hatched baby fish are called fry and when they are finger size they are called fingerlings. With a little extra time and care you can have fingerlings to put in your ponds and to sell to other farmers.
Here is a way to produce common carp. You will need two ponds – a spawning pond and a nursery pond. Spawning is when adult fish breed and lay their eggs. A spawning pond is a pond where fish can breed and lay eggs. The spawning pond is also where the eggs will hatch into fish fry.
The spawning pond
In a separate spawning pond more baby fish will hatch and survive because there are fewer predators and less disease.
When choosing a site for the spawning pond, look for soil that holds water. Dig a pond about 2m x 3m in size and about 1m deep. Leave the pond empty until the sun has baked the soil completely dry to kill any insects that might eat the newly hatched fry. Once the soil surface is full of cracks, let fresh water into the pond. When the water is at least 50cm deep, the spawning pond is ready for breeding stock. A mat of pond weeds such as water hyacinth, covering no more than a quarter of the pond area, encourages spawning as eggs are laid among the roots.
Choosing carp for spawning
When choosing carp as breeding stock, choose big, healthy adults that are ready to spawn. Females that are ready to spawn have soft swollen bellies. Males that are ready to spawn will secrete a white milky substance when gently squeezed. Choose about ten of the biggest, healthiest females and ten of the biggest, healthiest males.
It takes only one day for the fish to spawn. After one day, remove the adults from the spawning pond and put them back in the pond.
Carp eggs hatch in about two days. In a few days the fry will be about the size of an eyelash – 0.5cm long and very thin. When the fry are at least 1cm long, put them in a nursery pond. You can catch them by using a very fine mesh net or a net made out of loosely woven cloth. Handle them very carefully.
The nursery pond
The nursery pond is a little shallower than the spawning pond, but it is prepared in the same way. Dig a pond about 6m x 6m and about 70cm deep.
Let the soil bake in the sun. When the soil is full of cracks, sprinkle well rotted manure or compost and slowly fill the pond. The nursery pond must have an inlet for fresh water coming into the pond and an outlet for water to leave the pond. The outlet will prevent the pond from overflowing and washing away the carp fry. Don’t forget to cover the inlet and the outlet with a fine mesh to keep the fry in and the predators out.
If possible, feed the fry first with a little powdered egg yolk and, later, finely powdered oil cake (heat treated) and rice bran. Carp fry also eat small plants and animals that live in the water, and they will reach finger size in six to eight weeks. When your carp are fingerlings you can transfer them into your fish ponds or sell them to other farmers.
Adapted from DCFRN Notes No.35
Know your fish!
Tilapia mature at 3 to 4 months of age. When breeding begins, the male makes a round nest on the pond bottom by waving his tail back and forth. Then he attracts a female to lay eggs in the nest. The male fertilises the eggs, then the female picks them up and keeps them in her mouth to protect them. After several weeks the eggs develop into ‘fry’. They begin to swim around but keep near their mother’s mouth in case of danger. They leave the mother after two more weeks.
A female tilapia can reproduce 3 or 4 times a year, producing up to 1,000 eggs each time. It is easy to understand how a fish pond can quickly become overcrowded with small tilapia! Small fingerlings can be removed from the pond edges and sold to other farmers. When you see many small fish in your pond, this means it is time to prepare for a total fish harvest as overcrowded fish will not grow well.
D & M Murnyak