Came across this BBC piece, where Prof. Brian Cox states flathead catfish skin is covered with 700 taste buds per square centimeter and that catfish see the 3D picture of their world (the signal direction and intensity) by tasting the water, that is catfish is like one huge tongue.
It is pretty striking to imagine that catfish use taste/smell to see their environment the same way we use primarily eyesight and secondarily hearing to see and know what's around us.
 Is the entire skin covered in taste sensors?
 Is this an accurate description?
 Is this how all / almost all / most catfish perceive their environment?
Not knowing, just argumenting - a fish will only have taste buds if chances of percieving something are good enough
I would assume Lorricarids, being adapted to live in fast moving water, will not have these - fast moving water will wash anyting away, resulting in tasing things which are meters away, while not tasting things arount them due to the direction of the current.
Catfish is a rather large group of fishes, after all, living in a very different areas.
Perhaps predatory catfish, living in stagnant water, would benefit from thes buds. but others? I wonder
Loricariids have them as well. Most pleco keepers have watched their plecos "taste" something with their caudal fin to ensure it is food before turning to face the item and eat it. Better to check it out with your tail in case you have to swim away fast.
Several studies on this but few that compare the ability across families.
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I liked seeing the BBC video for the first time, especially since it uses a flathead catfish as it's my favorite species I fish for on the Lower Colorado River on the Cali/Arizona border. The first catfish I ever kept as a pet was a black bullhead I caught as a young boy, kept it in a washtub in my bedroom then. As I would watch it in the tub one day, lying still, I touched it's tail with a twig, no reaction. I then touched it's tail with a large worm and it immediately wheeled around and attacked the worm, devouring it with great relish! That convinced me about something I'd read at the time about their ability to taste through their skin. At that early time I would read in fishing magazines about how some said to avoid their whiskers as they have stingers on 'em!