FISH HATCHERY: AN IMPORTANT ASPECT OF AQUACULTURE

The Nigerian aquaculture sector is growing at a very exponential rate and diversifying in a parallel manner. This welcomed trend still at its primordial stage is faced by numerous bottlenecks which if left unattended, will definitely shorten the lifespan of the success achieved in this economically viable aspect of the agricultural sector.

Of all the hurdles faced by individuals active in this sector, unavailability of viable fingerlings and juveniles has been the major setback. A greater percentage of aquaculture practitioners in the country largely depend on fingerlings and juveniles from the wild as stocking materials for their pond. In a modern and agriculturally competitive world, this practice cannot be sustained due to the fact that most fishes are seasonal breeders and there is always a scarcity of stocking materials also called fish seed when it is not breeding season.

It is necessary to bear in mind that the demand for aquaculture products is always on the rise both globally and locally. Hence, to maintain a constant supply of stocking materials for a fish farm, farmers resort to hatcheries to provide an all year round supply of stocking material.

HATCHERY
A fish hatchery is a special place where fish breeding; egg fertilization, incubation, hatching and rearing through the early stage of life into fingerling is carried out artificially. It is seminal in modern aquaculture as it allows regular supply of pond stocking materials for farmers and it also allows the improvement of the genetic and phenotypic traits of the cultured aquatic organism as desirable traits can be enhanced and undesirable traits checked or controlled through cross breeding.

In general, a hatchery can be situated on an aquaculture farm (incorporating a hatchery with normal fish production) with the sole purpose of providing fingerlings for the farm or it can be carried out in entirety on a farm (focusing solely on fingerling production).

REQUIREMENTS FOR FISH HATCHERY
Irrespective of the method of production – sole hatchery production or incorporated production, a fish hatchery requirement doesn’t change. Some of the major requirements for a fish hatchery include:

• Water: Abundance of water suitable for fish production all year round. The water should be monitored meticulously for negative changes in its chemistry and measures should be taken to counter such changes. The water should have a neutral pH, be well aerated and free from pollutants.
• Availability of feed: Although young fish generally feed on planktons, in a confined environment the supply of plankton may be limited and lead to the malnourishment of the stock. Hence, a farmer should adopt methods that will promote plankton division, proliferation and growth. Alternatively, he should ensure that there is ample supply of feed necessary for the feeding of his young fishes. The feed should be able to provide all the necessary nutrients required by the young fishes in appropriate quantity. Such feed can be purchased from an aquaculture feed store.
• Breeding fish: Breeding materials (breeding fish) should be available. Because of the sexual dimorphism in fish, it is required that farmers should obtain sexually matured male and female fish with favourable traits to serve his hatchery. Breeding materials should have a good history of rapid growth rate.
• Market: If the farmer is not operating the hatchery to feed his fish farm, there should be a ready market to patronize him of his stock.
• Equipment: There should also be hatchery equipment and supplies available. These include pond or tanks, buckets, chemical, containers, nets, aerators, filters, etc. Each of these equipment play a crucial role in the success of a hatchery. For example, a fish pond or tank is filled with water and is used to house the breeding materials and the eggs are placed in containers during spawning. For better observation of fish, a small tank is preferable. It is advised to keep male and female fish in separate tanks.

BASIC HATCHERY METHODS
Fish reproduction both in the wild and in confinement involves egg release, fertilization, incubation, hatching and growth. This process is what the farmer tries to mimic to the best of his ability in a fish hatchery.

Egg release: Egg release in fish can be natural or induced. In most commercial setups, egg release is usually induced by injecting hormones such as Suprefact and Ovaprim which cause the female fish to release eggs every three months. When a female fish is prepared to reproduce, she is filled with eggs and appears larger than normal because of her swollen abdomen. These eggs are released from the abdomen of the fish into its external environment awaiting fertilization by the sperm of the male fish.

In hatcheries, egg releasing is enhanced by the farmer who gently applies pressure to the abdomen of the fish in a downward manner that causes the release of the eggs through their genital opening. The released egg is collected in a container while they await sperm from the male fish.

Fertilization: Sperm is obtained from the male fish by slaughtering them and extracting their testis. The testis is then sliced into two or more quadrants and each placed in a clean, thin cloth material and squeezed to obtain the sperm in a container. The sperm obtained from the male fish is then introduced into the container holding the eggs and mixed to promote better fertilization chance of the eggs. Sperm from one male fish can be used to fertilize eggs from up to thirteen female fishes.

Incubation and Hatching: after fertilization has been carried out, the eggs in the egg holding container is covered with water and aerators placed in them to enhance aeration. This medium is now placed in a conducive environment usually 30°C for incubation to occur. Hatching usually occurs within two to three days in most fishes.

Growth: immediately after hatching, the young fish experiences rapid growth till they attain a certain size before they are removed from the container. Different fishes possess different growth rate depending on various reasons, hence, farmer needs to observe this phase meticulously to prevent the predation of larger fish on smaller ones.

NOTE: before embarking on fish hatchery operations, seek professional help to prevent total failure of the process as young fish handling and management can be very volatile and can lead to loss of resources if not carried out properly.