How to Identify Smallmouth Bass

To identify Smallmouth Bass (Micropterus dolomieu), look at these key features.

Physical Characteristics

Body shape

torpedo

Coloration

Typically bronze to brownish-green on the back and sides, fading to a white or cream belly. Often exhibits 8-16 dark, vertical bars or blotches along the sides, which can be more pronounced in younger fish or in certain environments. The dorsal fin is usually dusky, and the caudal fin is often dark with a lighter margin.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Upper jaw does not extend beyond the rear margin of the eye (a key differentiator from Largemouth Bass)., Shallow notch between the spiny and soft-rayed dorsal fins., Eyes are typically reddish-brown., Scales on the cheek are smaller than those on the operculum.

Dorsal fin

Two dorsal fins, broadly joined, with 9-11 spines in the anterior (spiny) portion and 13-15 soft rays in the posterior (soft-rayed) portion. The notch between the two sections is shallow.

Tail fin

Slightly forked caudal fin, typically dark with a lighter margin.

Pectoral fin

Paired pectoral fins, relatively small.

Distinctive fins

Anal fin with 3 spines and 10-12 soft rays. Pelvic fins are thoracic.

Identification Tips

1. 1

   Mouth Size

   The most reliable distinguishing feature: the upper jaw of a Smallmouth Bass does not extend beyond the rear margin of the eye when the mouth is closed. In contrast, the Largemouth Bass's jaw extends well past the eye.

2. 2

   Dorsal Fin Notch

   Smallmouth Bass have a shallow, barely noticeable notch between their spiny and soft-rayed dorsal fins. Largemouth Bass have a deep, distinct notch, almost appearing as two separate fins.

3. 3

   Coloration and Markings

   Smallmouth Bass typically have vertical bars or blotches on their sides, often bronze to brownish-green. Largemouth Bass usually have a prominent, irregular horizontal dark stripe along their sides.

4. 4

   Scales on Cheek

   Smallmouth Bass have smaller scales on their cheek compared to the scales on their operculum (gill cover). Largemouth Bass have uniform-sized scales on both the cheek and operculum.

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