Aquaculture for all

Bringing the Ocean Home with DIY Aquaculture

Trout Nutrition Health +11 more

Once the sole domain of wealthy businessmen and fish experts, aquaculture is becoming increasingly attractive as a domestic amateur hobby. Adam Anson, reporting for TheFishSite, finds out what it takes to get started.

The incentives that fish farming has to offer become increasingly attractive as people continue to embrace the concept of home-raised food production in all of its forms. Whilst aquaculture is perhaps most accessible to rural communities, it is also now available to urban dwellers. Grown indoors or out, this new trend can provide a cheaper alternative to the high prices that retailers charge for fish, whilst enabling a more manageable degree of food safety and sustainability.

Fish farms pose a greater challenge to amateur farmers than vegetable plots, but they are relatively easy to farm by comparison with livestock, needing less space and providing high meat outputs in return for the time consumed managing them. The input costs are also relatively low, most fish converting about 65-70 per cent of feed into meat.

For many, the question isn't if they want to farm fish, but how. The options are both varied and numerous, but the kind of operation budding fish farmers should choose to undertake depends on the territory, time and money they have available.

The System

The simplest way to produce fish is in a specially made cage, which can be lowered and moored into a body of water. Although this system is very cheap, the farmer must first have access to a pond and cannot expect to produce great quantities of fish.

Another simple and inexpensive method of production uses a continuous source of natural cold water and diverts it into a pond. The inflow and outflow can be easily managed with well positioned pipes. This system produces a good quantity of fish, but again, access to natural water supplies is crucial and water regulations will need to be discussed with local authorities.

Those unable to access local water sources may consider building a home recirculating system, the productivity of which will vary greatly depending on how well it is built and managed. Controlling temperature, removing ammonia and waste, and oxygenating the water are all of great significance to this system. For this to be achieved home recirculating systems must be fitted with additional components, including: a solar dome - to keep the water warm; a drum clarifier - to collect and remove organic material; a biofilter - to remove ammonia; an aerator, to add oxygen to the water; and a source of emergency power in case of a power outage.

For those who fancy a bit more of a challenge, and would like to produce highly sustainable and organic produce, aquaponics may be the answer. Rather than using artificial components to control water quality, waste and feed, aquaponics sets out to develop miniature and balanced ecosystems by growing fish in conjunction with different kinds of plants. Vegetables can be grown to maximise food output. The plant feeds upon the waste in a fish tank and filters the water in the process. Aquaponic systems are normally managed in greenhouses in the same manner as hydroponics. Pumps and aerators must also be included in the system and management can become extremely complicated and time-consuming.

The Fish

Choosing which kind of fish to raise is the next big question. Considerations involve its market price, taste, growth rate, ability to reproduce, how easy it is to culture the young and how readily available the necessary feed is. Some fish are omnivores which makes them relatively easy to manage as they feed on natural food resources occurring in the pond, but many fish require fishmeal and fish oils to survive and supplies can be both insustainable and expensive. To compensate for higher feeding costs, however, most carnivorous species fetch higher market prices.

Fish species that are hardy and can tolerate unfavourable culture conditions will survive better in relatively poor environmental conditions (e.g. tilapia). Besides the effect of the environment on the fish species, the influence of the species on the environment should also be considered when introducing a new fish species. For warm water species tilapia, catfish, carp and bass, are recommended, whilst the most suitable cool-water species are trout, salmon and perch.

Farmers can choose to grow more than one type of fish species at a time, but extra considerations must be taken on-board for this. Each fish species has a certain feed preference, making feed management a more complicated process. However, if it is well balanced a farmer can take advantage of the different feeds available at different areas of the system. Consequently, total fish production can be raised to a higher level than would be possible with only one species.

The Management

Eggs can be harvested and fertilized or, fertilized eggs, known as eyed eggs can be purchased quite readily. For the first few months they are raised in rearing ponds or hatching trays away from the main pond. Fish develop in a series of identifiable stages. They begin life as an egg, then grow into a larvae, a fry, a fingerling, a young fish, a juvenile and finally an adult. As egg and larva fish feed on their own reserves, but by the time they become fry their yolk sacs are depleted and they must instead rely on an external, varied food source.

Natural fish food consists of phytoplankton, zooplankton, periphyton and water plants, produced in the pond itself. Largely this consists of phytoplankton which can be increased by the addition of fertiliser to the pond. The natural food supply of carnivorous fish includes insects, small fish & crustaceans. Poles and branches can be added to the pond, which are soon colonised by a variety of tiny organisms that can be eaten by the fish.

The rest of the fish's diet is attained by supplementary feed. Typical examples of supplementary fish feed are rice bran, broken rice, breadcrumbs, cereals, cereal wastes, maize meal, Guinea grass, napier grass, fruits, vegetables, peanut cake, soybean cake and brewer's waste.

To achieve a high production of fish in the pond, regular maintenance and monitoring is also vital. Daily management includes: checking the water quality (oxygen, pH, salinity, colour, transparency, temperature, etc.); checking the pond for possible water leaks; cleaning the screen of the water inlet and outlet; observing the fish while they feed to check for fertiliser levels and possible disease; looking out for predators; and removing aquatic weeds growing in the pond.

June 2009
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