Black spots on largemouth bass are nothing new, but it seems this year that more fish with these spots have been seen at marinas and on social media than usual. The random black blotches cause concern for some anglers, but they really shouldn’t. In fact, they are just a fun feature that Mother Nature sometimes throws at fishermen.
“There are multiple causes for this in bass,” says Mike Wood, the former inland fisheries chief for the Louisiana Department of Wildlife and Fisheries. “The melanosis, which is simply black pigment blotches on the bass, is more than likely caused by excess sunlight or some genetic trait in the fish. It’s more likely that those irregular black spots are just unique personality marks on healthy bass.”
Some have suggested that the spots occur because fish has been caught and poorly handled before, or that specific water conditions contribute. Either way, Wood said, if the fish appears healthy, there’s not anything wrong with it just because it has the black blotches.
Fish showing the black spots have been caught and documented at several reservoirs in February, including Toledo Bend, Caney Lake and Claiborne Lake.
“Over the years, I’ve had the opportunity to examine thousands of bass from water bodies across Louisiana,” Wood said. “Some water bodies always seem to have a higher frequency of bass with the pigmentation. I believe that’s due to localized genetic pools of the trait. To me, they are just neat beauty marks.”
What it is
The technical explanation of melanosis is that it is caused by skin cells that cannot regulate pigment production normally. The melanin production in those cells is greatly increased, which causes the black spots, or more accurately, “hyperpigmentation.”
It’s important to know that this is not normally any kind of disease. If a fish is skinny or looks generally unhealthy, there may be something else wrong with it. Melanosis is also present on occasion in catfish and trout. The condition doesn’t affect the fish in any way, other than make it look different. It also is not a “warning sign” that anglers should not eat the fish if they so desire.
Most cases of melanosis occur in bigger bass, those weighing 2 pounds or more. The spots are generally irregular and can appear anywhere on the fish from head to tail, or even on the fins.
Biologists have reported that “black bass blotching” has become more common in recent years in reservoirs or ponds.
The situation is similar to a common marking found in crappie, where a definitive black line goes from a crappie’s “nose” all the way down its back. These fish are commonly referred to as “blacknose crappie.” That is a genetic marking, and the specific trait is almost the same in all the crappie that possess it.
“Largemouth bass with melanosis are just kind of cool to look at,” Wood said, offering a non-biological opinion just a fisherman. “Every time I catch one, or when we’d find one doing shock surveys, I hold them up a time or two and look. They deserve a second look for sure.”
Wood retired from LDWF four years ago but still manages private waters as a technical consultant. You can get in touch with him through his website, mikewoodfisheries.com.
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