Monday, June 8, 2015

Cages for fish rearing

Here on our tilapia farm we have three different types of cages. There are several materials which you can use to make the structure with and also those which form the netting of the cage itself. You can buy them ready made on places such as Ebay or you can make them yourself.

We bought ours used, and did a few repairs to them to get them ready for the fish.

Our cages which are 3m x 2m are on aluminum frames and the cage itself is plastic coated wire. This has advantages and disadvantages. The advantage is it is lightweight. When you are moving or lifting it , once filled with fish any extra weight just makes your job more difficult.
The metal cages could take fish beginning at 50grams, any smaller and they could swim out through the space between the chainlink.

tilapia cage

The other type we have is heavy duty plastic on a wooden frame. These are 2m x2m and are heavy.This is due mainly to the frame as all the wood here in Brazil is hardwood. Yes the wood will last virtually forever but it is heavy. The plastic netting is very strong and the gaps are smaller which allowed us to buy smaller (less expensive) fish. When using the plastic cages, we could buy fish which were 30grams.

The third type which we bought, we didn't use as, although it was lightweight, it was cumbersome. This was made out of pvc pipe and was rigid.

The truth is you can make the size you want or need using most anything.
The 3m x2m has the capacity to hold 900 fish and the 2m x2m can hold 600. We always kept the amount less than this as we didn't want to stress the fish.

To keep it afloat we had a welder make small baskets into which we put empty plastic bottles. These had originally held industrial cleaning products but once empty were sold off for various uses. If you use this idea, be aware that after a time in the sun, the plastic does become brittle. It is always a good idea to have spares around, otherwise your fish could escape as the cage would sink on the side where your container has filled with water.

It is also necessary to have a lid on your cage for a couple reasons.
  1. Fish can jump out.
  2. To keep fish eating birds out. This includes herons, egrets, cormorants etc
  3. To keep birds from eating the fish food.

Along the top edge of the cage you will also need to put a fine mesh. This should be tied down to the cage. This keeps the fish food from floating out before the fish eat it. 

Sometimes you may notice the tilapia have red or bleeding mouths when raised in a cage. This is from hitting the side of the cage, trying to get out. This however never affected resale value as we sold by the kilo. 

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