Wait... Carp Don't Have What Organ?!

These picky fish lack an internal organ commonly found in almost 3/4 of all fish, how is that possible?

fly fishing for carp

March 2024

Those picky spooky fish that reject your flies, and bask in the sun just out of the reach of your cast, lack an internal organ commonly found in almost 3/4 of all fish. An otherwise important organ that should make them easier to catch... in theory.

Carp don't have stomachs. They simply pass whatever they eat directly into their intestines. Without a stomach, they can't really feel full, or ever stop eating. Bizarre, especially considering how picky they are for anglers.

Scientists have confirmed that these fish, along with others, including pufferfish and wrasse, have lost stomachs and the genes responsible for creating acid in stomachs. This was possibly caused by diets that didn't require the usual acid to aid in digestion. For example, eating shellfish and corals, organisms rich in calcium carbonate, neutralize acid, and overtime could have led to the loss of stomach acid genes in ancestral fish and the eventual disappearance of a stomach. Modern carp seem to manage just fine with the help of specialized pharyngeal teeth (teeth found in the back of their throat) to kick-start digestion.

Grass carp also make the most of things without stomach. They can eat between twice and three times their body weight in a day, gaining as much as ten pounds in one year. You'd think that would give anglers ample shots at hooking these veggie-carp. Yet they’re considered one of the spookiest, most skittish fish in freshwater.

So if you're feeling like they're getting the best of you… don't give up, plenty of opportunities exist, because carp can't stop eating.