A Clarias hybrid and its implications
by Nonn Panitvong

o, a few of my international friends have asked what is up with my post on Facebook with a photo of a Clarias in it, why do so many like and share?, what did I write?. Here is my broken English translation for all of you. I guess this simple calculation can apply to many species and situations.


Clarias - hybrid species

Clarias - hybrid species

This post became major news in Thailand, news website, television and radio are all talking about this and I hope that I did deliver the message to a lot of people. Clarias catfish (or Walking Catfish) are a popular food fish in Thailand. In the past, the most popular, and the most delicious of them all is Clarias macrocephalus, however, this species only grows to 25-30 cm. and they grow quite slowly thus they are not commercially viable in large numbers. So Clarias gariepinus, the African Giant Walking Catfish was imported and they were artificially bred with the native C. macrocephalus, to create the hybrid that grow quite big, quite fast and quite tasty. They named this hybrid BigOui. It was a major commercial success and it became the majority of Clarias being sold in the markets anywhere in the kingdom.

Now a large majority of us are Buddhist and we believe in making merit by freeing the suffering life. Catfish in the market or in the aquaculture ponds are destined to live a short life and die as food, so people believe that buying them and releasing them in to nature is a good deed. As a conservation biologist, I would like to let you all know that this hybrid alien does not belong in our waters, NEVER, and here is some simple calculation to show you why.

1. Clarias are omnivores meaning that they eat both plants and animals and according to research the ratio is about 1:1.
2. They eat about 5% of their body weight.
3. The market size of Clarias in the market is about 3 fish/Kg.
4. And for simplicity of calculation I will assume that the Clarias are released into a good location, that they all are able to fill their stomachs everyday. I will also assume that their size remains constant because otherwise it will be too complicated for me to calculate, (i’m a field/conservation biologist and we are not supposed to be good with maths).
Our scenario is this guy decides to buy 1,000 kg of Clarias which would consist of 3,000 individuals and release them into this said pristine water, and i’m not joking, people in my country do buy this many fish for release.

So According to our facts they will eat about 50 kg. of food/day (1,000 * 5%), and of this 50 kg., half of it or 25kg. will be animals: 25 kg = 25,000 grams. The animals (fish, shrimp, snail) that will fit a Clarias of this size would be about 2-3 cm. and they would weigh about 5 grams, so these Clarias will eat 5,000 individuals (25,000/5) of animals per day or 1.7 individual/Clarias/day which is very highly possible and that will be 1,800,000 individual/year (5,000*360).

These 1.8 million animals that are being eaten by the Clarias, the large majority would be native species, some are young and of a highly important food species, some are endangered species, some are a small species that would normally be preyed upon by larger native species. These native species are playing the same games by the same rules and they know each other’s game very well. They are in a balance, and are now adding a large quantity of hybrid Clarias into this equation which will instantly wreck the whole balance of this food web. It is like you are in your village and suddenly a large group of carnivore like lions or tigers are released into your area and you are defendless against them, or maybe the predator just showed up in the area and started hunting you like in the movies. That would be what our native species feel when you release the hybrid Clarias into our water ways.

I don’t believe that you would gain any merit from such an act and I would strongly discourage you all from doing this. That would be what our native species feel when you release the hybrid Clarias into our water ways.


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