your internet guide to all things catfish
|Thoughts on a Catfish|
by John Sankey
here are so many living things - so many ways of living! And, some of them illustrate better than any textbook the long route that life took from molecule to mammal. One of these is the genus Clarias, the 'Walking Catfish'.
They are true fish. But, they
One species, Clarias batrachus, is occasionally found in tropical fish stores. It has a body shaped like a fish, scaleless like an amphibian, and four pairs of barbels. It comes in a wide variety of colours: white, tan, gray, brown, or albino. Males have spots on their dorsal fin and females don't. It moves on land by curling its tail forward then jumping, like a frog with only one rear leg, keeping itself upright with its stiff front fins. Mine is less than a foot long, but can move so fast it might get away from me if I don't have a butterfly net in hand.
Clarias are not appreciated by fastidious aquarists, for they dismember and eat any fish smaller than they are. It's not a quick process either. Clarias have a small mouth, with no teeth - their prey has to be reduced to swallowing size by shaking. They normally live on muddy bottoms, and can't see more than a few centimetres, so they have to locate food almost entirely by smell and motion. And, in the artificial environment of a small aquarium, smells can spread so evenly that even that fails to help them locate food - they have to just charge around until they run into it. I feed mine dried food, and earwigs in season.
They are also a useful example
of the resilience of biodiverse ecosystems. The
June 1969 National Geographic (135:846-851) contains
photos of the panic-driven campaign that occurred
when they were discovered in the Everglades. The
living things of thousands of pools were killed
with rotenone until it was discovered that everything
except the catfish were being killed - they simply
climbed out of the poisoned pools and walked to
the next one. The campaign was abandoned - the Everglades
given up as lost forever by the authorities. Then,
it was discovered that alligators love Clarias
- the alligators of the Everglades have never been
better fed! I am not aware of a single species whose
existence in the Everglades was endangered by the
addition of Clarias. (Incidentally, the same
is true of house sparrows, starlings and purple
loosestrife, all of which have engendered equally
panic-stricken campaigns around me in Canada.)
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