How To Tell Spotted Bass from Largemouth at a Glance

Some anglers have difficulty telling spotted bass (Kentucky bass) from largemouth, and since in many places, including my home Ozark streams, the regulations are different for the two species, every angler should know how to tell them apart.  Even though many fishermen release their bass no matter what the species, in the Meramec river system in Missouri, spotted bass are invasive and have caused a serious decline in native smallmouth population, and those who care about the smallmouth should actually keep and kill all the spotted bass they legally can.

I remember the first spotted bass I ever caught.  I was in my early teens, perhaps 12 years old, and my grandfather had taken me to Whitewater River to trap minnows.  It was a long drive just to trap some bait, but Grandpa grew up in the area and I'm sure he was just wanting to revisit some old haunts.  I was, as always, fishing while he watched his minnow traps, and caught a bass that even back then, I knew was different from either the largemouth or smallmouth I'd caught previously.  Granpa just called it a "lineside", but I knew it wasn't a largemouth, and when I got back home I tried to find out what it was.  The Conservation Department had published a book on Missouri game fish with black and white photos, and it was there that I saw that my bass was a spotted bass.

Maybe, because I'm an artist and was an artist of sorts from the time I was a small child, I had trained myself to see details that others miss.  But I've always been able to tell spotted bass from the very similar appearing largemouth at first glance, as I lift them out of the water.  Indeed, I've often said I can tell them apart blindfolded, by feel.  Spotted bass scales are slightly saw-toothed on the outside edge, while largemouth scales are smooth, so when you feel them, the spotted bass feels slightly rough, the largemouth very slick.  But you don't have to feel them to see the difference.

It seems that some fishermen misidentify them because they have learned to feel the tongue.  Spotted bass have a small patch of teeth on their tongue, a spot that is slightly raised and feels like coarse sandpaper.  Largemouth supposedly don't.  But I have a largemouth mounted and hanging on my wall that has a tooth patch.  It seems about 10% of largemouth have a tooth patch.  It is raised like spotted bass but the teeth are much smaller so it feels only slightly rough, but it can be there.

The other thing that many anglers seem to remember is that spotted bass have smaller mouths.  Their upper jaw (maxillary) extends only to about even with the rear of their eye, while largemouth maxillaries reach well past the eye.  However, the mouth must be almost fully closed to check this characteristic, and if the largemouth is under about 10 inches, its maxillary might not be obviously past the eye.

So how do I tell them apart just at a glance (and I'm certainly not the only fisherman who can do so)?

Below is an illustration I did of both species.  I used good, clear photos to begin with, and enhanced the details--photos of fish usually have reflections and glare from their wet, slimy skins that often obscure details.  What is immediately obvious is that the two fish actually do look quite similar.  They are both basically greenish, and they both have a blotchy horizontal bar running from eye to tail down the middle of their sides.  You can also see in this illustration that the maxillary is slightly smaller in the spotted bass, but the size difference is really not too obvious, and could be missed or misread.

The upper fish is the spotted bass, the lower is a largemouth.  Now, here is the same illustration, with the differences I find very noticeable and that I use to identify the two species.

The area of the body marked A on both fish is the first thing I see.  Spotted bass have obvious rows of small spots in this area that, at a glance, form thin, dark lines.  Largemouth may or may not have some spots, but they are never as dark and noticeable and they do not form those thin lines.

The second thing I see is the area of the body marked B.  This is the portion between the lateral line and the dark band.  On spotted bass, the scales in this area have dark edges and each scale is plainly visible as a result.  On largemouth, these scales are not edged in darker colors and thus are not obvious.

Those two things immediately tell me whether the fish I'm lifting out of the water is a spotted bass or a largemouth.  I've also noted a couple other differences.  The notch between the spiny dorsal fin and soft dorsal fin, marked C, is deep on largemouth, with the membrane barely connecting the two fins.  On spotted bass it is significantly shallower, the membrane broadly connecting.  

And finally, the area marked D.  The scales on the lower cheeks and in front of the pectoral and pelvic fins on spotted bass are very small, much smaller than those on the upper gill cover and the rest of the body.  On largemouth, these scales are larger, a little smaller than the other scales but not nearly as small as they are on spotted bass.