I’ve never eaten a carp, but I’ve always heard that you should remove the mud vein before eating them and that you should watch out for “floaters” (loose bones suspended in the flesh, as in suckers). They say the fish will taste “muddy” if you don’t remove that vein, thus the name. Some folks, who know nothing about fish, envision a section of intestine, like in shrimp. The mud vein in fish though is neither a vein, nor a part of the intestines. It’s a strip of darker meat about halfway up the side of the fish and runs from gill to tail.
Some references say that it’s at the same point as the lateral line. The lateral line on a fish is heavily laden with nerves and is used to detect movement in the water around them. That helps them locate prey, avoid predators and stay in their schools more easily. There is supposedly a higher level of fat in that area and the meat is darker due to that section being more saturated with blood. I assume the extra blood is to keep the nerves in good health. Since poisons and heavy metals tend to be deposited in the fish’s body fat, both that area and the fat along the belly are more likely to be contaminated and taste peculiar. It may be best, then, to remove both.
While I’ve never tried removing the vein from them before cooking, bass, catfish and even bluegill show evidence of the so-called vein, as do most fish. I HAVE learned that fish tend to taste less “fishy” if you scrape the vein off before eating them. It removes quite easily after cooking, and you’ll find the seam between the back meat and rib meat underneath. I don’t know if removal after cooking would work for carp or not; I know that it does for trout, tilapia and salmon. Other folks suggest keeping the fish in clean water for a few days to let them “flush out,” just some do with turtles. Whatever method you choose, please don’t let your catch (or your meal) go to waste. © 2013-