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
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.
are omnivores meaning that they eat both plants and
animals and according to research the ratio is about
eat about 5% of their body weight.
market size of Clarias in the market is about
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
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.