The Difference Between Large And Smallmouth Bass (How To Easily Tell Them Apart)

largemouth  bass and smallmouth bass lying on a table

It is easy to see how people can confuse the two. Deep bodies, big mouths, similar size, and often inhabit the same waters. However, Smallmouth Bass and Largemouth Bass are two species, unique with their own biology and effective fishing tactics.  

Here's a quick guide to reliably identifying Largemouth vs. Smallmouth Bass and more importantly, information to better understand them so you can become a more effective angler. 

Largemouth vs. Smallmouth Bass

To a seasoned angler, identifying fish is often a matter of a quick glance. However, even expert fish handlers can be forced into a second glance and a closer inspection to tell the difference between Largemouth Bass and Smallmouth Bass.

While there are a lot of indicators and idioms people may generally use to identify fish, they can often be unreliable at times due to individual fish variations within a species of fish.

In this post, we've  broken it down into the “Most Reliable Indicators” which are almost always true and easy to rely on, and “Less Reliable Indicators”, which should be used to support each other and not relied upon alone for fish identification.

Most Reliable Indicators For Identifying Bass

These are almost always true and easy to rely on. When supported by one another, you have a guaranteed identification.

1. Jaw Length In Relation To The Eye

Perhaps the most effective and quickest indicator that you can rely on is looking at the size of the jaw. When you close the mouth of a bass, the length of the jaw will differ between a Largemouth and a Smallmouth bass.

bass identification

Though more apparent with fully closed mouths, the Smallmouth (top) will have a jaw that does not extend past the rear point of the eyeball. A Largemouth (bottom) will have a jaw that extends past the rear point of the eyeball when fully closed.

On a Largemouth, the rear portion of the upper jaw extends beyond the eye. (Imagine drawing a vertical line tangent the back of the eye). On a Smallmouth, the rear portion of the jaw will not extend beyond the back of the eye. Remember that this only works when the mouth of the fish is closed in a natural position. Though you can rely on this method with pretty good certainty. They don’t call them a Largemouth and Smallmouth for nothing

jawline of largemouth bass extends past eye

Largemouth Bass with fully closed mouth. Note how the haw extends well beyond the rear portion of the eye.

2. Vertical Stripes vs. Horizontal Bar

Another fairly reliable indicator is looking at the orientation of the prominent dark markings on the side of the bass.  Largemouth Bass almost always have a darker horizontal line of rough shape running down the length of their body in line with the middle of their tail.

Smallmouth Bass, on the other hand, are generally characterized by an irregular striping consisting of short sections of dark vertical bars on the body.  

largemouth horizontal stripe vs smallmouth vertical stripes

Largemouth (top) are generally characterized by a dark lateral line stripe down the length of their body. Smallmouth (bottom) are generally characterized by lots of vertical dark barring down their side. Oftentimes Largemouth and Smallmouth will have a similar size and shape, so it comes down to key characteristics.

3. Dorsal Fin

Lastly, you can look at the dorsal fin of the bass. The dorsal fin of bass consists of two main “humps”. A Largemouth Bass has two separate “humps” of dorsal fin with a deep notch separating them. A Smallmouth Bass has one continuous fin consisting of two “humps”.

smallmouth bass dorsal fin

Notice how the dorsal fin on the Smallmouth dips down, but continues as one single and continuous fin. A Largemouth bass will have these two fins separated.

Less Reliable Indicators Of Bass Identification

These are indicators that should not be relied on as the sole means of identification, even though they sometimes are. While generally true, these characteristics can sometimes be attributed to unique differences in individual fish. When these characteristics are supported by other identifying traits, you can reliably tell the difference between a largemouth and smallmouth bass.

1. Color

Often, you can have a pretty good idea of what kind of fish it is based on a quick flash of the fish on your line. Largemouth Bass are generally a noticeably green color. Smallmouth on the other hand, can be described as more bronze, olive, or brown colored.  

color differences of bass

Smallmouth Bass (top) are usually described as a bronze, brown, or olive colored fish. Largemouth Bass (bottom) are usually described as being a green colored fish.

Bass Biology: 

Now that you know how to visually tell the differences between these two bass, let’s look at getting a better understanding of how these bass function and where they live to give you the edge as an angler.

Largemouth Habitat

Largemouth Bass are the epitome of a sit-and-wait ambush predator. These Bass are generally found hiding in and amongst cover. This often means hiding in the depths of a root wad or undercut, lurking under the shadow of a boat dock or bridge piling, hiding in a dead submerged tree, or even tucking back in the grass and reeds in a little pocket.

Largemouth Bass generally prefer slower and undisturbed areas of water. You won’t find them anywhere near strong current. They are more of a warm-water fish than Smallmouth Bass. Though these two Bass can often be caught in the same water body, the Largemouth Bass will almost always seek out shallower and warmer waters.

Smallmouth Habitat

Smallmouth Bass are a slightly colder-water lover of the North American Bass and are more adept at living in swifter water environments.

While also an ambush predator, Smallmouth Bass are also very much a pursuit predator. These fish are found not sitting and waiting in cover, but actively patrolling in and around cover that may be holding small fish.

You can find Smallmouth Bass moving around rock-piles and drop-offs along with foraging in submerged timber. Being a colder water fish, they’re often found in much deeper waters than Largemouth, only entering shallow waters during spring spawn when the water temperature is around 60 degrees. You can also find smallmouth bass moving into the shallows at night to feed.

Practice Safe Fish Handling

Remember, when taking a closer look at your newly caught fish, be sure to practice safe fish handling. While “lipping” bass is generally an acceptable way to handle them. Remember to only lift vertically or offer support under their belly so as not to damage or hyperextend their jaw.

  1. Handle Fish with Wet Hands

  2. Limit Time out of Water

  3. Do not Bend Jaws Open. Lift Vertically or support the Belly

Have fun out there and hopefully you can have some fishing days catching multiple species of Bass in the same water. Use this quick guide to help identify Largemouth vs. Smallmouth Bass.

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How To Identify Bass (VIDEO)

About the Author

When I'm not bass fishing or looking for steelhead in my home state of Oregon I can be found working on house projects dreaming of my next fishing adventure. I started this website to share just some of the things I've learned along my fishing journey, and the many things I'm still learning. Enjoy!