Cage Culture of Tilapia
The traditional method of raising tilapia in earthen ponds has been accompanied by two other techniques during the 20th century: cage raising and tank raising. Each technique comes with its own pros and cons and a method highly suitable for one situation may be far from ideal under other circumstances. In this article, we will take a closer look at the cage culturing of tilapia.
Raising tilapia in cages
Raising tilapia in cages makes the tilapia much easier to harvest. When tilapia is grown in ponds, the farmer usually have to drain the pond and use seines to harvest the fish after each growing cycle, a practice which is both labor-intensive and stressful for the fish.
A tilapia cage typically consists of mesh and lets the water circulate freely while keeping the fish inside. Cages are commonly used when tilapia is raised in rivers, reservoirs that mustn’t be drained, natural lakes, estuaries, and coastal embayments. Experimental projects are also being carried out where tilapia is raised inside cages placed in cooling water discharge canals.
Placing tilapia cages in public waters is illegal in certain parts of the world or requires a permit. In some areas the legal status for tilapia cages in public waters is unclear which can create problems for you in the future if you go ahead.
Generally speaking, tilapia cages are more frequently found in large bodies of waters than small ones, since small bodies of water are less stable and more easily affected by the waste products emitted from tilapia cages. If you place tilapia cages in a small body of water (<5 acres / <2 hectares), you should be aware that the waste products can cause a sharp decline in available oxygen in the water, causing fish mass-deaths. To prevent this from happening you can install mechanical aeration. Water changes will also work, but may be impractical.
Tilapia cages are either individually moored or linked together. Piers and rafts are commonly utilized by tilapia farmers and attaching cages to ropes suspended across the surface is also popular.
Pros and cons
Pros
- It is easier to harvest tilapia from cages than from ponds.
- It is easier to make sure the tilapia gets the food when you carry out supplemental feedings.
- In densely stocked cages, the normal reproductive habits of tilapias are disrupted. You can therefore keep males and females together without having to worry about uncontrolled breeding. If spawning does occur, the eggs will normally fall through the mesh before the male gets a chance to fertilize them, provided that the mesh you use is larger than 1/10-inch.
Cons
- Supplemental feedings might be easier in a cage than in a pond, but you will on the other hand be forced to feed your fish a lot more since they won’t be able to swim around looking for their own food. Cage grown tilapia do have limited access to natural food but it is rarely enough to sustain them – especially not if you want them to grow fast. You will also be forced to feed your tilapia food of a higher-quality since you must make sure that it contains everything they need, e.g. sufficient amounts of all necessary vitamins and minerals.
- When tilapia is raised in cages, most farmers opt for a very high stocking density. Living in such a crowded environment is stressful for tilapias and weakens their immune system. If parasites, virus or similar find their way into the cage, the fish won’t be able to put up much of a fight and mass-deaths can occur. You can decrease the risk by feeding your fish a high-quality diet and making sure the water values are optimal.
- Unlike a tank, a cage is open for predators unless the mesh is very fine and durable. Unlike the more natural situation in a pond, tilapias trapped in a cage won’t be able to escape if attacked by predators small enough to swim through the mesh.
- Cages are vulnerable to storms.
Choosing tilapia species
Many different tilapia species, hybrids and variants are commonly grown in cages, such as Blue tilapia (Oreochromis aureus), Nile tilapia (Oreochromis niloticus), and the man-made variants Taiwan Red and Florida Red. The Nile tilapia is a very fast grower, but is not as cold tolerant as the Blue tilapia. Taiwan Red and Florida Red are not particularly cold tolerant either, but they are highly priced on the food market for the reddish coloration and they grow pretty fast.
As you can see, each tilapia comes with its own strengths and weaknesses. When choosing tilapia for your cages, several factors should be taken into consideration, including climate, water conditions, salinity and which growth rate you require. Also keep in mind that certain species and hybrids may be banned in your area. Checking up on local legislation in advance can save you a lot of trouble in the long run.
Cage placement
- Placing tilapia cages in stagnant water is usually not a good idea.
- Placing the cages closer to each other than 4.5 meters (15 feet) will increase the risk of really poor water quality. The greater the distance the better.
- Placing the cages less than 90 cm (3 feet) from the bottom will increase the risk of disease.
- Ideally place the cages in a place exposed to a lot of current, since that will help remove waste products and aerate the water. Extremely rough waters should however be avoided.
