Eye coloration, particularly shades of red or orange, is a distinct feature that allows anglers and naturalists to narrow down identification. This reddish hue is not universal among all members of the Centrarchidae family, commonly known as sunfish, which includes all black bass species. By focusing on this specific trait, along with other physical markers, it is possible to accurately distinguish a few prominent species that exhibit this signature eye color.
The Definitive Red-Eyed Bass
The primary species recognized for its red or reddish-orange eye is the Smallmouth Bass (Micropterus dolomieu). It is characterized by bronze or brown-olive body coloration, which tends to be darker in clear water environments. A reliable way to identify this true black bass is to examine the jaw; its upper jawbone, or maxilla, extends only to about the middle of the eye, distinguishing it from the Largemouth Bass. Smallmouth Bass also display a series of dark, vertical bars or blotches along their sides.
The overall body shape is streamlined and muscular, built for speed and power. Unlike the Largemouth Bass, the Smallmouth’s two dorsal fins are clearly connected, with only a shallow notch between the spiny and soft-rayed portions. The intensity of the eye color can range from a deep red to a reddish-orange, sometimes becoming more pronounced in spawning males.
Beyond the Smallmouth Other Red-Eyed Species
The most common fish confused with the Smallmouth Bass is the Rock Bass (Ambloplites rupestris). Although a member of the sunfish family, it is not in the Micropterus genus and is sometimes called “redeye” or “goggle-eye” due to its prominent, bright red eyes. The Rock Bass is differentiated by its more robust, stocky, and laterally compressed body shape, which is noticeably shorter and deeper than the Smallmouth’s streamlined form.
Rock Bass possess five to seven anal spines, most commonly six, while the Smallmouth has only three. The Rock Bass’s body is typically golden-brown to olive with rows of dark dots below the lateral line, a pattern the Smallmouth lacks. A third contender is the Redeye Bass (Micropterus coosae), native to the southeastern United States, which also has striking red eyes and a body that is less elongated than the Smallmouth, often showing reddish-orange tints on its fins.
Understanding the Red Pigmentation
The red pigmentation in the eyes of these fish results from specialized biological components. The coloration is linked to carotenoid pigments, such as astaxanthin, which create red, orange, and yellow hues. These pigments are obtained through the fish’s diet and deposited into the eye’s iris in pigment cells called erythrophores. The intensity of the red is influenced by the fish’s diet, genetics, and the clarity of the water it inhabits.
In some cases, the redness is enhanced by the tapetum lucidum, a reflective layer behind the retina rich in blood vessels. This layer reflects light back through the retina to improve vision in low-light conditions. The high concentration of blood vessels contributes a reddish tint to the eye’s appearance, helping these visual predators hunt efficiently in the clear, often deeper water they prefer.
Ecology and Distribution
The Smallmouth Bass thrives in cooler, clearer water, distinguishing its habitat preference from that of the Largemouth Bass. They are typically found in large, clear lakes with rocky shoals and in moderately flowing rivers and streams with gravel or rubble bottoms. The native range encompasses the St. Lawrence River-Great Lakes system and the upper and middle Mississippi River basin.
These fish are highly mobile, sometimes traveling significant distances in rivers, and are intolerant of high turbidity or siltation. As a top predator, the adult Smallmouth Bass primarily eats crayfish, small fish, and aquatic insects. Their preference for clean, cold-to-cool water means their presence often serves as an indicator of a healthy aquatic ecosystem.