What is that yellow streak down the back of my catfish?

yellow catfish fillet

Well, it’s probably not because catfish are cowards. But many catfishers have certainly noticed the yellow, to dark yellow, to sometimes brown streak on the fillets of catfish. The yellow is usually seen on top edge of the fillet (near where the dorsal fin had been) and sometimes on the lower edge (near where the pelvic fin had been). It’s not, as some have guessed, iodine, or some other terrible toxin. But it’s found as a streak on the edge of the fillet because that is the fatty part of the fillet. The fat itself is not yellow, but yellow-pigmented compounds that are fat soluble will accumulate in the fat and cause it to become yellow. These yellow compounds are actually antioxidant chemicals that are good for you. They’re called xanthophylls, but are better known as carotenoids. And as you may have known, they are in many vegetables and of course carotene in carrots is one of the best known of these. While carotene is orange, the xanthophylls, such as lutein and zeaxathin found in catfish are yellow. And then there are other xanthophylls that are red, such as astaxanthin, found in shrimp, lobster, and salmon.

Fish don’t naturally have these pigments, but must get them from the environment, from what they eat. Now as you probably know, catfish are omnivores, which means they are opportunistic eaters and will eat just about anything. This means aquatic plants, other fish, vegetation, algae, fish eggs, crayfish, snails, aquatic bugs, minnows, decaying vegetation, dead fish, dead bugs, leeches, worms, but their main diet is insects, small fish, and vegetation. In the farm-raised catfish that you buy at the grocery store (if you had some bad luck catching your own), the yellow color would come from natural sources like algae, snails, vegetation, and shad (stocked with the catfish), plus from the corn in their feed. The catfish in stocked ponds and lakes should be similar, but river catfish probably would have a little more variability.

And if you just want the yellow color gone, I’ve heard you can soak the fillet in salted ice water overnight and the fillet will become pristine white. I’ll be trying this, and other methods, soon. I’ll give you a heads up on the results. So, even though the yellow streak in catfish can be considered a good thing – “sun kissed”, that same fat that the yellow dissolves in is also a great reservoir for the off-flavor, dirt-smelling compounds that are often associated with catfish. Even though there’s not really a link between the yellow color and the off-flavor (probably because the two maximize at different times of the year) some people remove the fat and say it helps the taste of the fillet.

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