The Ozark sculpin was first described scientifically in 1985. Before that, it was considered synonymous with the mottled sculpin. Then, in 2010, researchers recognized the knobfin sculpin as a separate species and split it away from the Ozark sculpin. Among these fish, there are consistent differences in body form and in DNA. These indicate that what used to be considered “Ozark sculpins” occurring in the Current, Eleven Point, and White river drainages were a separate species, the knobfin sculpin.
Meanwhile, the Ozark sculpins in the Osage, Gasconade, and Black river drainages retain the name “Ozark sculpin.”
Sculpins, as a group, have very large mouths. The head is broad and flattened, tapering abruptly into the rather slender body. Scales are absent, but small prickles are often present on the head and body. The dorsal fin is divided into two distinct parts; the forward part contains spines, but these are soft and flexible, superficially resembling soft rays. The pectoral fins are large and fan-shaped. The pelvic fins each contain 1 stiff spine and 3 or 4 soft rays. The rear margin of the tail fin is rounded.
The Ozark sculpin can be distinguished from other Missouri sculpins by the following:
- The lateral line is incomplete, ending beneath the base of the soft dorsal fin.
- The two sections of the dorsal fin are clearly joined.
- There usually are wavy bands across the second dorsal fin, making it look marbled.
- Spawning males have a blue chin and belly.
- Dorsal fin spines number 6–7.
- Pectoral fin rays number 13–15.
- The membrane connecting the two sections of the dorsal fin is only slight to moderate-sized.
- There is moderate to strong pigmentation (dark markings) on the lower surface of the body cavity (you’d have to cut the fish’s belly open to see this).
- It occurs in the Osage, Gasconade, and Black river systems (not in the Current, Eleven Point, and White river systems).
Like our other sculpins, the overall color is variable, tending to match substrate color where found. The Ozark sculpin has the back and sides dusky and mottled, with the background color brown to olive. There are usually 4 (possibly 3–5) indistinct dark saddle marks across the back. A dark bar at the base of the tail fin is usually a thin crescent that is straight or slightly concave on its hind margin. Spawning males are dark grayish black to nearly black, with bluish-green color on the chin and belly, and a yellow to orange stripe on the outer edge of the first dorsal fin.
Similar species: Five species of sculpins occur in Missouri.
- The knobfin sculpin (C. immaculatus) is most similar. It too has an incomplete lateral line, clearly joined dorsal fins, wavy bands across the second dorsal fin, and breeding males with a blue-green chin and belly. However, it has a different dorsal fin spine count (8–9); has a different pectoral fin ray count (16–17); has a comparatively wide membrane connecting the two sections of the dorsal fin; and it has very little pigmentation in the lower surface of the body cavity. Also, the knobfin sculpin occurs in the Current, Eleven Point, and White river systems.
- The mottled sculpin (C. bairdii) occurs in the Osage, Gasconade, and Meramec systems, and in small tributaries to the Missouri and Mississippi rivers in the northern and eastern Ozarks. The mottled sculpin has a more rounded (less deep and compressed) body; the two sections of the dorsal fin are narrowly joined or are nearly separate; and spawning males are black, lacking blue coloration.
- The banded sculpin (C. carolinae) occurs in many of the same stream systems as the Ozark sculpin. Note the banded sculpin’s complete lateral line and its broad, distinct dark vertical bar at the base of the tail, angling forward toward the belly.