How To Know the Number of Fishes A Pond Can Take?

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This singular question or issue can make or mar a fish farm business. Overstocking of fish ponds has been the detriment of many fish farms in Nigeria. Here is how to know the number of fishes you can put in your fish pond. Do you just gauge with your eyes that the pond can take 1000 fishes or 2000 fishes?

Imagine you put 20 children in a small face-me-I-slap-you kind of room. That’s overpopulation. In fish parlance that is what we call an excessively high stocking density.

Issues that shouldn’t normally occur would arise. Water to bathe would be scarce. The toilet and other facilities would be strained. Diseases would thrive and easily spread.

There would be competition for food and afterwards, the bully of the house would be clearly identified.

He would continue getting the best food, be bigger and stronger to continue his bullying. However, imagine if they were just 2 fishes in that pond? (Yes, it is fish we were talking about all along, what were you thinking?)

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What is a fish pond carrying capacity?

Every pond has what is called a carrying capacity. What this means is there is a maximum weight of fishes that the pond can support.

Once the weight is achieved the fishes would stop growing. The weight in that tank cannot exceed the carrying capacity. For instance, you know this white iron tanks?

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It contains 1000 litres of water. With an average calculation of 10 litres to 1 fish, that means it can only support 100kg of fish.

What this means is that if you put 1 fish in there, all other factors being equal, the fish can continue growing till it reaches 100kg in size. If you put 2 fishes there, they’ll grow till they each reach 50kg in size.

The total weight of fishes in that pond sustainably can only peak at 100kg. If you put 100 fishes in there, they would grow till they reach 1kg each in size. If some of them have to continue to grow bigger, then some of them would die. You’ll just notice that all the total weight of fishes in the pond doesn’t exceed its carrying capacity.

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This carrying capacity can only be calculated not from the dimensions of the pond, but from the actual litres of water that is put in the pond. Don’t forget that you wouldn’t fill the pond up with water to the brim. So for better results, you need a bigger pond.


Items to tick before you stock your pond

Here are some tips that should guide you before you can calculate the stocking density of the fish pond based on the following formula’s for you to know what quantity of fish you should put in your fish pond.

1. Water management: How available is water on the site? Can it be changed quickly, regularly and frequently? How many thousands of litres are you able to pump in and how long that takes? This would let you know if you can plan to change water daily, and therefore stock more. However, if you have to change the water every 3 days, you would have to stock less.

2. Management ability: How many staff do I have on the farm, how skilled are they? How efficient are they? Should 1 person take care of 10,000 fishes?

3. Power availability: You probably need power to change the water in your ponds. This can either be government supply or a generator and fuel. These are costs that should be factored in. If we cannot have access to power to change the water more frequently, then we should stock less.

4. Your financial Power: How many fishes can you raise? If you budget N450 to raise a fish to table size of 1kg (this is only possible using local feeds – for more advise on fish feeds check here), how many fishes would you be able to raise conveniently without running out of funds? We all know that one fish farmer who is looking for quick sales because he cannot afford to feed again and thus gets swindled by fish buyers because of his desperation. Why not stock what you can afford to raise without borrowing money, and start the marketing of your fish 2 weeks before you run out of feed.


Calculation time!

After this, you can then use the following formulas to calculate how many fishes your pond can take.

This varies from pond to pond. Different stocking densities for different pond rearing systems. You can read up on the FAO’s stocking density here. All calculations are in meters.

  • For the Earthen Ponds: Length * Breadth * Height *2/5 (Measurement in Feet)
  • The Mobile fish Pond: Length * Breadth * Height *5/3 (Measurement in Feet)
  • Concrete Pond: Length * Breadth * Height *5/3 (Measurement in Feet)
  • For the Tanks: Use the FAO standard of 10 litres to 1 fish at your peril. Experience shows that the fish always hangs when you use that stocking density. That is why most people you see want to sell off thier plastic tanks. For tanks, I would advise you use use a standard of 50  litres per fish.

For more on what you need to know before you start your fish farm project click here

To know how to identify the best fingerlings or juveniles to stock on your farm click here.

You can reach Akinfish at any time on 08161385163 for ideas or counsel, you can also ask your comments or questions in the comment section.


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