Tilapia Farming in Lakes, Cages, and Tanks
Tilapia Farming in Brazil
Before arriving in Brazil, I had never heard of a tilapia. There were a few in the lake in front of our new home when we arrived, and after a year, we decided to net the lake and sell the fish. These sold very quickly, and it was at that point we started to seriously think about raising them to sell commercially. In this state in Northern Brazil, there is a requirement of 40% more tilapia because of the growing domestic market.
We now have over 10,000 fish and are set to double this number in the next few months. We are currently using three methods here on our farm: free swimming, in cages. and in purpose-built tanks.
Tilapia can be raised in ponds, lakes or tanks. We have chosen to have lakes dug, which are fed by the water table.There are several lagoons in the area, some are deeper than others. We wanted to make sure we would still have water at the driest time of year so we can keep producing fish, albeit smaller quantities.
Some tilapia farms lined their lakes with clay. These are then continually filled with water and then drained when the fish have been sold. Our lakes use the water table and are therefore cheaper to run as we don't have the added expense of pumping water to fill them.
Lake and Pond Aeration
With so many fish in a body of water, we need to aerate our lakes. The wind, which is a constant for several months of the year here, will add oxygen to the water by breaking the surface tension of the water. With extra added oxygen we will be able to farm more fish and as such make more money. Without aeration, ammonia builds up as a result of fish waste. The aeration promotes aerobic bacteria which clean the lake and reduce the ammonia.
There are several different methods for aeration. Here in Brazil, we have seen the paddle aerators which sit on the surface of the water. Think of a paddle boat going down the Mississippi and you will understand what I mean.
There are types that sit on the surface and push air down, and others that sit on or near the bottom and deliver air through a diffuser which will spread the air over a larger area.
There are also windmills that will aerate ponds and lakes. These are an excellent idea when there is no electricity present. Solar panels are also used to drive a small pump to circulate water.
Below is a photo I took from our balcony. This is one of our lakes in front of the house. This aerator is a 1.5 horsepower and will pull water from a depth of 1.8 meters. We also have a less powerful one in another lake that pulls water from 1.2 meters. This we use in a lake that has less fish and more natural wind.
Tilapia Fish Cages
The cages we use are plastic coated chain link. This is on a metal frame and we have used 4 x 50L plastic bottles to keep each afloat. These cages are 3m x 2m and can take 900 fish each.
We have also bought others that are on a wooden frame with heavy gauge plastic netting as the cage. These will be used for our new fish as the holes are too small to allow a 30g fish to pass through. These are 2m X 2m and 1.2 meters deep. At maximum water level, they can take up to 600 fish.
Feeding Cost of Tilapia
The cost of food to feed tilapia is high. We have seen many people digging lakes here to put the tilapia in but they don't realize that you have to provide food for them for 6-8 months without a return on your money. Once you have all your equipment, the cost of the food is the greatest expense. As such we have sought different methods of feeding. We are currently using duckweed which is floating plant. We have constructed ponds to grow this and we feed this to our fish every other day. This has cut our food bill down drastically.
The other option is to feed every other day. They will grow slower but it is estimated that in the same time frame your fish will be 10% smaller. If you have the time to leave them longer you will save more money feeding them every other day.
Another viable option is delayed feeding. If your pond or lake is rich with algae, you can delay feeding your young fish for 2 months. They will gorge on algae, and save you the cost of two months worth of commercial feed.
- Duckweed. Could this plant save the world?
For some duckweed is a menace, for others it's a Godsend. Find out why we have built duckweed ponds here on our farm in Brazil.
A Bit More Information About Tilapia
In parts of Asia, they will put tilapia in the flooded rice fields. When the rice is ready to pick, the tilapia are also ready to catch.
The type we have are an African Nile variety. This variety grows fast and is slower to breed than others. Although new to the western palate, the tilapia were farmed in Ancient Egypt.
They are very hardy and can survive in water temperatures to 40° Celsius(104°F). Although for optimal growing it should be 28-30° Celsius (82-86° F). In parts of America, they use tilapia as a low-cost method to keep the algae down in the water systems.
Tilapia eat a variety of foods, and as such are an economical fish to feed. In some areas, farmers will add manure to the water to encourage algae to grow. The fish then eat the algae, as mentioned previously.This is much cheaper than commercial fish foods.
Mistakes to Avoid When Raising Tilapia
As newbies to fish farming, we have made some mistakes and are now rectifying these.
Our first mistake was putting the fish into the lake without cages. We were advised to do this but there are a few problems with this method.
The first issue is that tilapia can begin to breed at 4 months. They build nests which are depressions in the the sand. See photo below.This makes the bottom uneven for netting purposes and allows the fish to pass below the fishing net. It also leads to erosion of the banks.
The second is, this increases the amount of fish in the lake which are competing for food. So the original stock we paid for are getting less food and hence growing less. We have been advised that this leads to stunted growth in fish.The answer to this is to net it frequently to remove as many fish as possible. We are doing this several times a week at the moment and putting the fish we catch into cages. We have noticed the fish are smaller but once they are in cages, they continue to put on weight and although not as big, equally as heavy and they are sold by weight not by size.
We have also introduced peacock bass and other predator fish into the lake. They will help control the numbers by eating the young ones.
Protecting Your Hands
If you are working with tilapia, you'll need gloves. When caught in a net, they splay their dorsal fin. This will damage your hands if you aren't wearing a suitable pair of gloves. Also, to secure the fish before removing it from the net, I insert my index finger into its mouth and with my thumb in the gills. This locks the fish in my fingers allowing my other hand to work the line free. Tilapia have a serrated mouth, and removing one fish isn't a problem. But try 20, 50 or 100 and with them thrashing and trying to escape, the skin on your thumb will be raw by the end of the day!
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© 2011 Mary Wickison